STEMscopes Georgia Science Student Notebook Physical Science by acceleratelearning

Physical Science STEMscopes Georgia Student Notebook

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Physical Science Notebook

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GEORGIA Student Notebook – Physical Science ISBN: 978-1-946725-79-0

Published by Accelerate Learning Inc., 5177 Richmond Ave, Suite 800, Houston, TX 77056. Copyright © 2017, by Accelerate Learning Inc. All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without prior written consent of Accelerate Learning Inc., including, but not limited to, in any network or other electronic storage or transmission, or broadcast for distance learning. To learn more, visit us at www.acceleratelearning.com

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GEORGIA

This Student Notebook is designed to be used as a companion piece to our online curriculum. The pages of this book are organized and follow the 5E model.

Student Handout

ENGAGE

A short activity to grab students’ interest

Student Journal

EXPLORE

A hands-on activity in which students get experience with the concept being taught

STEMscopedia

EXPLAIN

A reference material that includes parent connections, technology, and science news

Reading Science A reading passage about the concept that includes comprehension questions

ELABORATE Math Connection

A set of grade-level appropriate math problems that address the concept

Writing Science

EVALUATE

A writing prompt based on the concept studied in which the students can demonstrate what they have learned

Only student pages are included in this book and directions on how to use these pages are found in our online curriculum. Use the URL address and password provided to you by your district to access our full curriculum.

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Physical Science Student Notebook Table of Contents

Lesson PS1A

Atoms, Ions, and Isotopes PS1BC

Atomic Trends PS2ABC

Ionic and Covalent Compounds PS3AB

Conservation of Mass During Chemical Reactions PS4AB

Fission, Fusion, and Radioactive Decay PS4C

Nuclear Energy as an Alternative Energy Source PS5A and PS7D

Particles and Energy in Matter PS5B

Behavior of Gases PS6ABC

Solutions

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Page

1 25 51 83 111 131 147 169 187 iii

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Physical Science Student Notebook Table of Contents

Lesson

Page

PS6DE

217

Acids and Bases PS7A

Explaining Energy Transformations in a System

261

PS7BC

Thermal Energy

291

PS8A

Motion of Objects PS8BC

Newton’s Three Laws and Force of Gravity PS8D

Work, Mechanical Advantage, and Simple Machines PS9AB

Electromagnetic and Mechanical Waves PS9C

Wave Phenomena PS9DE

Sound and Light Waves

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243

315 335 361 385 407

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Physical Science Student Notebook Table of Contents

Lesson

Page

PS10AB

431

Electricity and Circuits PS10C

Magnetism and Electricity

455

Appendix Glossary

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479

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Physical Science

PS1A

Atoms, Ions, and Isotopes

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PS1A Atoms, Ions, and Isotopes

Student Handout Name:

Date:

Note: Only the first four energy levels are shown on this model.

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PS1A Atoms, Ions, and Isotopes

Student Journal Name:

Date:

Group:

ATOMS.COM PBL Entry Document Your science teacher was just informed that a local college is having a contest among area schools. The science department at the local college wants to create an educational website about atoms. Their goal is for a variety of learners to access the website and learn about atoms, ions, and isotopes, and their properties and characteristics. Your web design team’s task is to create a website that is both eye catching and informative. The local college has informed all area schools that the winning school will receive a $5,000 grant, which can be put toward the purchase of more science equipment and products for very cool science experiments. The actual website does not have to be created, just the idea for the website. To have your website design considered, you will need a display of your homepage and an example of an atom informational page. For the atom informational page, your team will need to select any atom from the periodic table and design graphics along with information so that a student accessing your website could learn about the chosen atom. The sample of your website can be created on either a laptop computer or posterboard. Your team will be given time to conduct research, develop your plan, and create a sample. You will present your idea to an audience in a 3-minute presentation. Divide your team into the following roles to complete the project: design team leader, atom expert, ion expert, and isotope expert. The number one rule is that you must stay in your own work area at all times. Thank you for helping to create a website design for our local college. This future website will be a great resource for students everywhere to learn about the importance of atoms in our world.

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PS1A Atoms, Ions, and Isotopes

Student Journal ATOMS.COM PBL Expert Roles Design Team Leader As the design team expert, your role is to ensure that your team successfully completes the task in the allowed amount of time. You will choose the element that your team will present. You will also keep track of all planning, encourage communication among team members, and make sure that all members of the team fully know and understand all parts of the plan. Team members will present your final design. Atom Expert As the atom expert, your role is to ensure that your team’s design has all the appropriate information regarding the characteristics of a neutral atom of the chosen element. This information will include the masses, electrical charges, and locations of protons, neutrons, and electrons, along with an explanation of the location of the element on the periodic table. You will design your section of the website. The team will present your final information regarding the neutral atom. Ion Expert As the ion expert, your role is to ensure that your team’s design contains all the appropriate information regarding an ion of the chosen atom. This information will include the masses, electrical charges, and locations of protons, neutrons, and electrons, along with an explanation of how the ion is different than the neutral atom. You will design your section of the website. The team will present your final information regarding the ion. Isotope Expert As the isotope expert, your role is to ensure that your team’s design contains all the appropriate information regarding an isotope of the chosen atom. This information will include the masses, electrical charges, and locations of protons, neutrons, and electrons, along with an explanation of how the isotope is different than the neutral atom. You will design your section of the website. The team will present your final information regarding the isotope.

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STEMscopedia: ATOMS, IONS, AND ISOTOPES

PS1A

Reflect Have you ever wondered what the entire universe is made out of? Well, it is simple. The entire universe is made out of matter. Of course, different objects are made out of different types of matter, but it’s all matter. Anything that has mass and takes up space is matter. Matter can exist in any state: liquid, gas, or solid. The only thing that exists in our universe that is not matter is energy. The smallest size that matter can be broken down into is called an atom. Atoms An element is matter that is made of identical atoms. An atom is the smallest unit of an element that has all of the chemical properties of that element. Every element that is found on the periodic table is made of different atoms. Parts of an Atom All atoms are made of three different subatomic particles: protons, neutrons, and electrons. Every element on the periodic table has a different number of protons, electrons, and neutrons. Study the nitrogen atom to the right. The center of the atom is the nucleus, and the outer rings surrounding the nucleus are known as the energy levels/electron clouds. Protons are positively charged subatomic particles that are found in the nucleus. Neutrons are neutrally charged subatomic particles that are also found in the nucleus. Electrons are found outside the nucleus and have a negative charge. Electrons are very tiny compared to a proton or neutron. One proton or neutron has a mass equal to the mass of 1,800 electrons. Together the protons and neutrons make up 99.9 percent of the atom’s mass. Since electrons have very little mass, the mass of an atom is found by adding the neutrons and protons together. The nitrogen atom to the right has seven protons and seven neutrons. Therefore, the atomic mass of the nitrogen atom is 14.

Look Out Atoms are so small they can’t be seen with a typical microscope. Some people think that atoms are solid dense balls, but they are actually 99.999 percent empty space. In fact the electron cloud is 10,000 times larger than an atom’s nucleus. The model below shows how an atom is composed of a large amount of empty space.

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STEMscopedia: ATOMS, IONS, AND ISOTOPES What Do You Think? Match the term with its description: ___Positive charge ___Smallest matter ___Atomic mass ___Where protons and neutrons are found ___Negative charge ___Where electrons are found ___Neutral charge

Neutron Proton Electron Energy Levels Atom Nucleus Protons Electrons Neutrons + Protons

Elements in the periodic table are ordered by their atomic number. The subatomic particle that determines the atom’s identity is the number of protons. The atomic number of an atom is equal to the number of protons that an atom has. Nitrogen’s atomic number is 7, so it must have seven protons. The number of neutrons and electrons can vary within a nitrogen atom, but it must always have seven protons to be a nitrogen atom. Oxygen has an atomic number of 8; therefore, an oxygen atom must have eight protons.

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STEMscopedia: ATOMS, IONS, AND ISOTOPES What Do You Think? Fill in the chart below each atom. Use a periodic table to help you identify the atom.

# protons ______________ # neutrons _____________ # electrons _____________ atomic mass____________ element _______________

Reflect Each of these two diagrams shows a different atom:

How are these atoms similar? How are they different? What conclusion can you draw about the properties of each atom based on its structure? Which element do these two atoms represent? Atoms of the same element can have different numbers of neutrons. Each of these atoms above has seven protons in its nucleus and seven electrons surrounding its nucleus. However, the atom on the left has seven neutrons in its nucleus, whereas the atom on the right has only six. Why is this significant?

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STEMscopedia: ATOMS, IONS, AND ISOTOPES The number of protons defines the type of element, yet atoms of the same element may have different numbers of electrons and neutrons. Because both atoms in the diagrams above have seven protons, they are atoms of the same element: nitrogen (N). They are also isotopes. What are isotopes? Isotopes are atoms of the same element that have different numbers of neutrons. Let’s consider another example. There are two natural isotopes of helium (He). One isotope has one neutron, and the other isotope has two neutrons. Both isotopes have two protons. Therefore, the mass number—the total number of an atom’s protons and neutrons—of the first helium isotope is 3 (two protons plus one neutron). The mass number of the second helium isotope is 4 (two protons plus two neutrons).

Reflect Helium has only two isotopes, but most elements have more. Iron (Fe) has more than 25 isotopes, but many of these isotopes are not very stable. The most abundant iron isotope has 26 protons and 30 neutrons. Therefore, this isotope has a mass number of 56.

Look Out There are several ways to write an isotope of a particular element. One way is to write the mass number as a superscript before the elemental symbol. Following this method, the two isotopes of helium are written as 3He and 4He. Another way is to use a hyphen to separate the name of the element and its mass number. For example, the two isotopes of helium are also written as helium-3 and helium-4. The average atomic mass of an element depends on its isotopes. On the periodic table, each element is listed with its atomic number above the chemical symbol. Below the atomic symbol is a decimal number that is the element’s average atomic mass. An element’s average atomic mass is the weighted average of the mass numbers of all the naturally occurring atoms and isotopes of that element. Most elements have more than one naturally occurring isotope. Do not confuse an isotope’s mass number with the average atomic mass of the element.

Reflect Have you ever been shocked by static electricity? If you have, then you have experienced the flow of electrons from one atom to another. When an electron jumps from one atom to another atom, it produces light and an electrical charge. Electrons can easily move from one atom to another atom. When you add or subtract electrons to or from an atom, you cause the atom to have an electrical charge.

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STEMscopedia: ATOMS, IONS, AND ISOTOPES Atoms of the same element can have different number of electrons. An atom can have different charges such as neutral, positive, and negative. The two subatomic particles that determine an atom’s charge are the protons and electrons. Not all atoms have an equal number of protons and electrons. The charge of an atom depends on the number of protons and electrons. For example, if an atom has three negative electrons and three positive protons, the atom is neutrally charged. If an atom has more positive protons than negative electrons, then the atom is considered positively charged. If you have more negative electrons than positive protons, the atom is considered to be negatively charged. Ions are atoms of the same element with a different number of electrons. An atom that gains or loses an electron is considered to be electrically charged. Atoms that are negatively charged are attracted to atoms that are positively charged. This attraction of opposite charges leads to chemical bonds being formed.

What Do You Think? Below are three atoms. These atoms all have three positive protons. Therefore, they are all models of a lithium atom. Label each ion with the type of charge it has: positive, negative, or neutral.

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STEMscopedia: ATOMS, IONS, AND ISOTOPES Connecting WIth Your Child Practice differentiating between a neutral atom, ions, and isotopes. Draw a shell of an atom for your student on a piece of paper, similar to the one to the right. Use M&M’s to represent the three subatomic particles (e.g., different colored M&Ms could represent different subatomic particles, such as red for electrons, yellow for neutrons, and blue for protons). Have your student practice creating different types of atoms, such as a neutral carbon atom, a possible carbon ion, and various possible carbon isotopes. For the sake of time, be sure to pick atoms that have small atomic numbers. Here are some questions to discuss with your child: 1. How do you know what element the atom represents? 2. What is the difference between an isotope and an ion? 3. What is the mass of the atom? 4. If you were to add an additional proton to an atom, what would be the name of the element the atom represents?

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PS1A Atoms, Ions, and Isotopes

Reading Science Name:

Date:

Group:

Rutherford’s Scattering Experiment 1

Today, it is well known and widely accepted that atoms are the smallest unit of matter. It is also known and accepted that atoms have a specific structure. They have a nucleus that contains positively charged protons and neutrally charged neutrons. Orbiting this nucleus are negatively charged electrons. However, these facts were not always known or accepted. There is a long history of the development, testing, and acceptance of the modern theory of the nature of atoms. This includes the discovery of atomic structure. Ernest Rutherford’s scattering experiment was one of the most important experiments leading to the nuclear model of the atom.

Let’s start at the beginning. The Greeks were the first to propose the idea of an atom. They defined this “atom” as a tiny particle that could not be divided into smaller particles. However, without the appropriate scientific tools, it was impossible for the Greeks to create viable experiments to test their ideas. It wasn’t until the early 1800s that the modern theory of atoms and of atomic structure got its start, thanks to John Dalton.

Dalton was one of the first scientists to use what he knew to support atomic theory. He was familiar with both the law of conservation of mass proposed by Antoine Lavoisier and the law of definite composition proposed by Joseph Proust. A scientific law is a statement that summarizes natural and physical phenomena that have been explored by many tests. A law tells what effect is always observed under a certain circumstance but does not attempt to explain why this will occur. Dalton used these two laws to propose what is now known as Dalton’s atomic theory. He stated that elements are made of very small particles called atoms. These atoms cannot be created or destroyed in a chemical reaction. Atoms combine with other atoms in whole-number ratios. He also proposed that the atoms of each element were different from the atoms of other elements, while each atom of an element is identical in every respect. (As new methods of investigation were developed, the suggestion that each atom of an element is identical was proven to be incorrect.)

Dalton’s atomic theory helped to explain some of the properties of atoms. However, it did not account for some of the behaviors of atoms, such as how they bond and react. Neither did it account for the composition of atoms. Scientists did not know or understand what atoms were made of. Therefore, there was still not enough evidence to support his hypothesis. Over two centuries, many different researchers have investigated and tested each part of the proposal.

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PS1A Atoms, Ions, and Isotopes

Reading Science 5

A hypothesis, or related group of hypotheses, can eventually become considered a scientific theory. This only happens if, over time, that hypothesis continues to offer valuable explanations of observed phenomena while being supported by wide-scale testing. While scientific testing never stops, a theory is generally considered to be true. However, a theory is subject to change as new information becomes known. Even today, most of Dalton’s atomic theory is still accepted and taught. The theory, however, has been modified to reflect new scientific understanding of atomic structure. These new discoveries were made possible by new technologies that allowed new methods of research.

In the 1820s, two scientists named Michael Faraday and William Crookes discovered that the atom was composed of even smaller parts. They called these subatomic particles. The first subatomic particle that they discovered was the electron. In the 1890s, another scientist named J. J. Thomson was able to describe the electron even better, including its charge of negative 1 (-1). But, it was still not known where this charge was located in the atom. They also did not know how this electron worked in regard to the other subatomic particles thought to be contained within the atom.

Then, in 1910, a scientist named Ernest Rutherford performed a set of groundbreaking experiments that led to the model of the atom that we know today. The experiment was called the Rutherford scattering experiment. Rutherford and his team began by using a radioactive source to create something called alpha particles. Alpha particles are basically helium atoms without their electrons. These high-energy particles were directed at a very thin sheet of gold foil. Surrounding the foil was a screen made of fluorescent material that would glow when struck by a particle. Based on what was known about atomic structure at the time, the team’s hypothesis was that most of the alpha particles would go straight through the gold foil. They thought they might perhaps see some particles moderately deflected to the side. However, the team did not expect to see several particles being deflected directly back toward the beam source. How was this to be explained?

Alpha particles have no electrons, so they have a positive charge. Remember, like charges repel each other. As the positive alpha particles traveled through the gold foil, most passed straight through. Some were moderately deflected. A very small number, however, were deflected back toward the beam source. As a result, the team concluded several things. First, the gold atom must be made of mostly empty space containing a sparse amount of electrons, as most of the alpha particles traveled straight through the gold foil. Second, there must be a positive charge somewhere in the atoms of the gold foil, as some of the positive alpha particles were deflected. Third (and perhaps most important), there must be a very small and dense nucleus within that atom that contains all of the positive charge, because a small portion of the positively charged alpha particles were deflected back to the beam source.

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PS1A Atoms, Ions, and Isotopes

Reading Science 9

These findings from Rutherford’s scattering experiment became new hypotheses that were tested in laboratories around the world. The repeated confirmation of each of these led to the nuclear model of the atom.

The story is not quite finished yet. By 1920, Rutherford had identified and named the proton as the particle in the nucleus that carried the positive charge. Scientists of the time soon knew that this was not a complete view of the nucleus. The atomic mass of each element did not match the atomic number, or the number of protons in the nucleus. They knew that the mass of the electrons was so small that it did not contribute significantly to the atomic mass. There had to be another neutral particle in the nucleus. This turned out to be the neutron, discovered by James Chadwick in 1932. The discovery of the neutron allowed scientists to explain why some elements did not have an atomic mass that was a whole number multiple of the mass of a proton. They were composed of a mixture of isotopes. Isotopes are atoms of the same element, thus with the same number of protons, which have different numbers of neutrons. This led to a modification of Dalton’s atomic theory. The portion that stated that each atom of an element is identical in every respect was found to be incorrect. Therefore, it was removed. The rest of the theory remained as Dalton had proposed, still supported by years of testing and scientific understanding.

Having been tested and confirmed for over two centuries, Dalton’s atomic theory is wellestablished. It can be readily accepted as a highly reliable explanation for the natural phenomena observed during chemical reactions. Following the identification of isotopes, a portion of his original theory had to be removed. This happened because of new understanding and new technology that allowed scientists to identify neutrons and protons and measure atomic numbers. Nevertheless, Dalton’s atomic theory still helps us explain the nature of chemical reactions today.

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PS1A Atoms, Ions, and Isotopes

Reading Science 1.

What theory did Dalton create based on his prior knowledge of the structure of atoms? A.

Atomic theory

Particle theory

Nuclear theory

Electron theory

Many scientists contributed to our current understanding of atomic structure. Which scientist discovered the negative 1 charge of an electron? A.

John Dalton

William Crooke

J. J. Thomson

Ernest Rutherford

What important component of atomic theory did Ernest Rutherford’s scattering experiment ultimately lead to? A.

Dalton’s atomic theory

The law of conservation of mass

The law of definite composition

The nuclear model of the atom

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PS1A Atoms, Ions, and Isotopes

Reading Science 4.

Why was it important for Rutherford and his colleagues to use alpha particles for their experiment? A.

Alpha particles have a positive charge.

Alpha particles are small.

Alpha particles have high energy.

All of the above.

Rutherford’s team concluded several important things from the scattering experiment. Which of the following was not one of the conclusions reached by the scientists? A.

Atoms must contain mostly empty space.

The space surrounding the nucleus contains a sparse number of electrons.

All of the negative charge in the atom is contained in a very small nucleus.

All of the positive charge in the atom is contained in a very small nucleus.

Rutherford’s experiment shed light on the structure of atoms. What was the most important discovery from this experiment? A.

Alpha particles have a negative charge.

The nucleus of the atom contains all of the positive charge.

Alpha particles can travel straight through an atom.

Some alpha particles were deflected as they passed through atoms.

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PS1A Atoms, Ions, and Isotopes

Math Connections Name:

Date:

Group:

Atomic Structure Part I: Isotope Symbols Isotopes are atoms with the same number of protons (atomic number) but different mass numbers. An isotope is represented by showing its element symbol with mass number as a left superscript and atomic number as a left subscript. Using this information and a periodic table, solve the questions below.

The isotope of carbon used in archaeological dating is electrons does an atom of have?

Element X is used in cancer therapy and as a source of gamma rays. Identify element X (its atoms contain 27 protons), and write the symbol for the isotope with 33 neutrons.

The isotope is used in smoke detectors for early fire detection. How many protons, neutrons, and electrons does an atom of have?

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. How many protons, neutrons, and

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PS1A Atoms, Ions, and Isotopes

Math Connections Part I: Isotope Symbols, continued 1.

Iodine (used to diagnose and treat thyroid disorders) has four main isotopes with mass numbers 123, 125, 129, and 131. Look up the atomic number of iodine. How many neutrons does each isotope contain? Give the standard symbol for each isotope.

An atom of element X contains 20 protons and 27 neutrons. Identify the element, and write the symbol for the isotope in the standard format.

Part II: Atomic Weight An element’s atomic weight is the weighted average of the atomic masses of the element’s naturally occurring isotopes. Atomic mass is frequently described in atomic mass units (amu; also called daltons), where 1 amu = 1.660539 x 10-24 g. Atomic Number Atomic Weight Atomic Weight of Hydrogen =(Mass 1H)(Abundance of 1H) + (Mass 2H)(Abundance of 2H) + (Mass 3H)(Abundance of 3H) (1.007825)(0.999885) + (2.014102)(0.000115) + (3.016049)(2x10-18) = 1.00794 3.

Carbon has three naturally occurring isotopes: , , and . has a natural abundance of 98.93% and isotopic mass of 12.000000 amu, has a natural abundance of 1.07% and an isotopic mass of 13.003355 amu, and has a trace (or negligible) natural abundance and an isotopic mass of 14.003242 amu. What is the atomic weight of carbon?

Nitrogen has two naturally occurring isotopes: nitrogen -14 (99.632%; isotopic mass = 14.003074 amu) and nitrogen -15 (0.368%; isotopic mass = 15.000108 amu). Calculate the atomic weight of nitrogen, and check your answer in a periodic table.

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PS1A: Atoms, Ions, and Isotopes

Math Connections Part II: Atomic Weight, continued 1.

Based on your answer to question 7, how many atoms of nitrogen are in a sample that weighs 1.25 g?

A sample of an unknown element contains 20 atoms with a mass of 10.0129 amu and 80 atoms with a mass of 11.0093 amu. Calculate the average atomic weight of the element. What is the element?

Naturally occurring lithium consists of two isotopes: (92.5%) with an isotopic mass of 7.016 amu and (7.5%) with an isotopic mass of 6.015 amu. What is the atomic weight of lithium? Check your answer in a periodic table.

Silicon has three naturally occurring isotopes: (27.9769 amu) with 92.23% abundance, (28.9764 amu) with 4.67% abundance, and with 3.10% abundance. Look up the atomic weight of silicon, and then calculate the mass of the third isotope.

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PS1A Atoms, Ions, and Isotopes

Writing Science Name:

Date:

LOOK

THINK Atoms are the building blocks of a chemical element. Without differences in the subatomic particles of a particular element, ions and isotopes would not exist. Think about the differences in the structure of atoms, ions, and isotopes. WRITE Using a balance as a model, describe the similarities and differences between atoms, ions, and isotopes in regard to the atomic structure, atomic mass, and the location and charge of subatomic particles. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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PS1A Atoms, Ions, and Isotopes

Writing Science Topic:

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Physical Science

PS1BC

Atomic Trends

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PS1BC Atomic Trends

Student Handout Name:

Date:

Elements on the periodic table are classified using physical properties exhibited by the element. As you complete the activity, answer the questions below. 1.

How does light reflect from the surface of carbon, copper wire, and the silicon lump? Does it appear metallic or nonmetallic (is it shiny or dull)?

Describe what happened when tapping the carbon sample with the hammer.

Describe what happened when tapping the copper sample with the hammer.

Describe what happened when inserting each element into the circuit. What evidence shows an element’s ability to conduct electricity in a closed circuit?

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PS1BC Atomic Trends

Student Journal Name:

Date:

Group:

Part I: Predictive Power and Ions

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PS1BC Atomic Trends

Student Journal Part I: Predictive Power and Ions, continued 1.

Using the clue cards, Student Guide, and periodic table, fill in the table below. Symbol

Element Name

# of Valence Electrons

Group

Cation or Anion?

Li S Ba F Al Kr

Part II: Metals, Nonmetals, and Metalloids 1.

The majority of elements are classified as _____________________.

The ___________ are found on the zigzag line.

Part III: Phase 1.

What can you infer regarding the phase of matter of the elements that were not listed in the chart in Part III?

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PS1BC Atomic Trends

Student Journal Reflections and Conclusions 1.

Based on the information on the clue cards and in the Student Guide, write an explanation regarding the pattern of valence electrons on the periodic table.

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 2. How is the group number related to the number of valence electrons for the representative elements, also called group A elements? _______________________________________________________________________________ _______________________________________________________________________________ 3. How are the valence electrons related to the ions formed? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 4. Why did we only put a symbol in the gases and liquids squares on the periodic table? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 5. Relate ions to the position of metals and nonmetals on the periodic table. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

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STEMscopedia: ATOMIC TRENDS PS1BC Reflect Over the course of history, people have used calendars and clocks as a way to keep track of time. Calendars are a simple way to chart days, months, and years in a table that is easily organized. In a similar manner, scientists have created a way to organize all of the known elements in table form. This is known as the Periodic Table of the Elements. Just like the columns in a calendar represent all of the similar days in the month (Sundays, Mondays, etc.), the columns in the periodic table represent elements with similarities. Think of what you have learned about elements so far. What are some ways that elements could be separated and arranged in a table?

Tables are a common way to represent similar items and to separate different items.

Development of the Periodic Table Early scientists used different characteristics of the elements to develop a basic elemental table. In the 1860s, a scientist named Dmitri Mendeleev proposed an arrangement of elements that formed the basis for what we know today as the Periodic Table of the Elements. Mendeleev based his table on the atomic mass of each element. Atomic mass is the average of the total mass of all the atoms of an element. The mass of an atom comes from both the number of protons and the number of neutrons in the atom. Mendeleev also ordered the elements into groups based on similar chemical properties. At the time of Mendeleev’s work, only 63 elements were known. However, Mendeleev’s table included empty spaces for additional elements. Although these elements had not yet been discovered, the patterns established by Mendeleev’s table “predicted” their existence. As later chemists discovered new elements, they were added to the periodic table. Other scientists expanded on Mendeleev’s organization of the elements. At nearly the same time as Mendeleev, a scientist named Julius Lothar Meyer wrote about similar trends in the elements. Meyer was able to show how certain elements behaved similarly based on the volume and weight of their atoms. Almost 50 years later, a British scientist named Henry Moseley used x-rays to order the elements based on the number of protons in each atom’s nucleus. Moseley’s method is how our current Periodic Table of the Elements is arranged.

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STEMscopedia: ATOMIC TRENDS Look Out The atom is the smallest particle that still retains the properties of an element. Atoms are made of smaller subatomic particles: protons, neutrons, and electrons. Protons and neutrons are located in the nucleus of the atom, while electrons are located in orbitals surrounding the nucleus. A way that elements are classiﬁed on the periodic table is by their valence electrons. Valence electrons are the electrons found in the outer electron shell. Do not confuse valence electrons with the total number of electrons in the atom.

Valence electrons are found in an atom’s outer electron The Modern Periodic Table shell. This atom has two In the current periodic table, shown on the next page, the elements valence electrons and four are organized sequentially based on an element’s atomic number. The total electrons. atomic number is the number of protons in the nucleus of an atom. The atomic number of the elements in the table increases as you move across to the right and down the periodic table. Our current periodic table is also organized based on the number of valence electrons present in an atom of each element. The horizontal rows of the table are known as periods. Elements in the same period have electrons that ﬁll the same valence shell. The number of valence electrons generally increases across the period. Vertical columns in the table are referred to as groups. All elements in the same group have the same number of valence electrons in their valence shell. Remember, valence electrons are responsible for the reactivity of the atom. So elements of the same group have similar chemical properties. Thus, the periodicity and trends of the periodic table are observed as a result of arranging elements based on atomic number and valence electrons.

periodicity: the property of repeating at regular intervals (or periods)

The Periodic Table of the Elements is also organized in other ways. Group A elements are known as the main group or representative elements. These elements are shown in yellow on the following table. Representative elements in the same group (or column) have similar chemical properties. Elements that are not part of the main group are shown in white in the table. Group B elements are referred to as transition elements. Below, the main part of the table includes the inner transition elements. These elements make up the Lanthanide series and the Actinide series.

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STEMscopedia: ATOMIC TRENDS Look Out

The transition elements, also known as the transition metals, are the largest category on the periodic table. When you hear the word metal, we tend to think shiny and magnetic solids. Even though these elements are metals, not all are solids. Some of the transition metals are lab-created, and mercury naturally occurs as a liquid. Some versions of the periodic table do not divide the elements into A and B groups. Instead, each column is numbered 1–18. Thus, Group 3B is simply Group 3 and Group 3A is Group 13. No matter how the periodic table is labeled, the same elements fall into the same groups. Main Group Elements of the Periodic Table Representative elements in the same group of the periodic table often have characteristics and properties that are similar. These elements form chemical families because they have similar chemical properties. Let’s look at four chemical families that are included in the representative elements on the periodic table. (To understand how elements in these An atom of oxygen has six groups react, remember: An atom is typically most stable when it has valence electrons. An atom a full valence orbital, so atoms tend to lose or gain electrons to reach of hydrogen has only one this point. Because most atoms with a low atomic number have eight valence electron. To ﬁll their electrons in a full valence orbital, this is referred to as the octet rule.) valence shells, two atoms of hydrogen bond with one • Alkali Metals: The alkali metals are in Group 1A of the periodic atom of oxygen (creating a table: the far-left column. Each alkali metal has one electron in its water molecule). valence orbital, which results in many of the chemical properties of these elements.

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STEMscopedia: ATOMIC TRENDS Look Out •

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Alkali Metals (continued): Alkali metals tend to lose their one ion: A charged atom. A valence electron easily, which produces a cation with a 1+ charge. positively charged ion (A cation is a positively charged ion that forms when an atom or forms when a neutral atom a molecule loses one or more electrons.) These elements are (protons equal electrons) highly reactive. At room temperature, they are solid with a metallic loses an electron. A appearance. They are malleable, ductile, and good conductors negatively charged ion of heat and electricity. Alkali metals include the elements, lithium, forms when a neutral atom sodium, potassium, rubidium, cesium, and francium. Though (protons equal electrons) hydrogen has only one valence electron, it is not an alkali metal gains an electron because many of its properties differ from those of other elements in the group. Hydrogen is a nonmetal, does not contain neutrons, and malleable: describes a is in a gaseous state. substance that can easily Alkaline Earth Metals: Elements in Group 2A are the alkaline earth be shaped with a hammer metals. These elements consist of beryllium, magnesium, calcium, (or a mallet) strontium, barium, and radium. Alkaline Earth metals have two ductile: describes a valence electrons, which they also lose easily to satisfy the octet rule. (When an atom loses the two electrons in its valence shell, that substance that can easily shell no longer exists. The new valence shell contains eight electrons be stretched into a thin wire and is therefore full.) When this occurs, a cation with a 2+ charge forms. These solid elements are highly reactive, malleable, and anion: a negatively ductile. They are also good conductors of heat and electricity. charged ion (charged Boron: Elements in Group 3A are part of the Boron family. The particle) that forms when elements in this group are boron, aluminum, gallium, indium, and thallium. Elements in the boron family have three valence electrons, an atom or a molecule gains one or more which they tend to lose to fulfill the octet rule. Boron is a metalloid, electrons while the other elements are metals. You will learn more about metalloids later in this section, but metalloids share properties of metalloid: an element both metals and nonmetals. that has some properties Carbon: Elements in Group 4A are part of the carbon family. The similar to metals and elements in this group are carbon, silicon, germanium, tin, and lead. some properties similar to Elements in the carbon family tend to gain or lose electrons based nonmetals on trying to fulfill the octet rule. Carbon is the only nonmetal in this group. Silicon and germanium are metalloids, while tin and lead are metals. Nitrogen: Elements in Group 5A are part of the nitrogen family. The elements in this group are nitrogen, phosphorus, arsenic, antimony, and bismuth. Elements in the nitrogen family have five valence electrons and tend to gain electrons to fill the octet rule. Nitrogen and phosphorus are nonmetals, but only nitrogen is in a gaseous state. Arsenic and antimony are metalloids, while bismuth is the only metal. Oxygen: Elements in Group 6A are part of the oxygen family. The elements in this group are oxygen, sulfur, selenium, tellurium, and polonium. These elements have six valence electrons, so they tend to gain electrons due to the octet rule. Oxygen, sulfur, and selenium are nonmetals, but only oxygen is in a gaseous state.

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STEMscopedia: ATOMIC TRENDS •

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Halogens: Elements in Group 7A are the halogens. The elements in this group are fluorine, chlorine, bromine, iodine, and astatine. The halogens have seven valence electrons. They react easily by adding one electron to fill their valence orbital, resulting in an anion with a 1– charge. At room temperature, a halogen can be a solid (iodine and astatine), a liquid (bromine), or a gas (fluorine and chlorine). Noble Gases: The six elements in Group 8A—on the far-right side of the periodic table—are the noble gases: helium, neon, argon, krypton, xenon, and radon. The noble gases are very stable because they already have a complete valence orbital. These elements are all gases at room temperature.

What Do You Think? Take a look at this diagram of the periodic table. It shows metals in orange, metalloids in green, and nonmetals in gray. Metals are shiny solids that are ductile and malleable, and they are good conductors of heat and electricity. Nonmetals are often gases or brittle solids that are typically insulators of heat and electricity. The metalloids are along a diagonal line that separates the metals from the nonmetals. Their properties are intermediate between metals and nonmetals. Based on their location on the periodic table, what types of properties would you expect of alkali metals? Alkaline Earth metals? Halogens? Noble gases?

Transition Elements and Inner Transition Elements Elements that are not part of the main group are found in two locations on the periodic table. The transition elements are in the middle region, and the inner transition elements are in the lower region. (Sometimes both groups of elements are together referred to as transition elements.) All elements in these groups are metals. Most have high melting points, and they often form colored compounds. They can react with other elements in various ways. Some of these elements are also radioactive, which means their atoms are unstable. Let’s look at these two locations on the periodic table in more depth.

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STEMscopedia: ATOMIC TRENDS •

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Transition Elements: Between the main group elements are the transition elements, seen in blue in the ﬁgure at right. These elements are metals and tend to lose electrons to form stable ions. The transition metals all have very similar properties that are common to many metals. Unlike most main group elements, they do not always use the same number of valence electrons in chemical reactions. This leads to a variety of possible charges for each element. For example, the element iron (Fe) sometimes loses two electrons to produce the Fe2+ cation, or it can lose three electrons to produce the Fe3+ cation. Lanthanide and Actinide Series: Two rows of elements lie below the main periodic table, shown in the image on the previous page, in yellow. These are the inner transition elements. The ﬁrst row of elements is actually part of Period 6 on the periodic table. It begins with the element lanthanum (atomic number 57) and ends with the element lutetium (atomic number 71). These elements make up the Lanthanide series. The second row of inner transition elements is part of Period 7 on the periodic table. It contains the elements that make up the actinide series. This set of elements consists of the element actinium (atomic number 89) through the element lawrencium (atomic number 103). All of the actinides are radioactive, and most do not occur naturally on Earth. Instead, they are synthetic—that is, chemists make them in laboratories. Sometimes a periodic table is drawn with lanthanum and actinium in the main body of elements.

Looking to the Future: Discovering New Elements All of the elements that have been discovered recently are very unstable substances and therefore do not occur naturally on Earth. Two elements, flerovium (Fl) and livermorium (Lv), were recently added to the periodic table. Scientists produced flerovium in 1998 by hitting plutonium with calcium ions. Flerovium is a radioactive element with an atomic number of 114 and an atomic mass of 289. This element was named after the physicist Georgiy N. Flerov, who was the founder of the institute where the element was discovered. The radioactive element livermorium was discovered in the year 2000 by hitting curium with calcium ions. Livermorium is a very unstable element that decays to form flerovium and other elements. Livermorium has an atomic number of 116 and an atomic mass of 293. It is named for the Lawrence Livermore National Laboratory, which partnered in the discovery of the new element. The number of known elements is currently 118. In order for an element to be added to the periodic table, it must be reviewed and named by members of the International Union of Pure and Applied Chemistry (IUPAC). In fact, only 114 elements have officially been accepted by the IUPAC and appear on the periodic table: the discoveries of four new elements have yet to be confirmed. Could scientists someday create element 119 or higher? (Because elements with so many protons do not exist in nature, chemists can only try to make them in laboratories.) The periodic table shows that more elements are possible, but creating heavier elements becomes increasingly difficult for scientists.

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STEMscopedia: ATOMIC TRENDS What do you know? The Periodic Table of the Elements categorizes elements based on their chemical and physical properties. Study the list of properties in the box below. Decide if each represents an element that is part of the following chemical families: an alkali metal, alkaline earth metal, halogen, noble gas, transition element, or inner transition element. Write your answers in the table below the list. Some of the answers may appear in multiple families. Property • • • •

Contains elements that do not typically react Elements donate two electrons to produce a cation with a 2+ charge Elements are mostly found in the solid state Elements donate one electron to produce a cation with a 1+ charge

Alkali Metals

Alkaline Earth Metals

Halogens

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• • • • •

Elements are found as a solid, liquid, or gas Elements are all gases Elements typically accept one electron to produce an anion with a 1– charge Contains many elements that are radioactive Elements can be found in different ionic forms

Noble Gases

Transition Elements

Inner Transition Elements

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STEMscopedia: ATOMIC TRENDS Connecting With Your Child Brochure of Chemical Family To help your child learn more about the chemical and physical properties among elements of the same family on the periodic table, work together to create a brochure describing one of the following chemical families: alkali metal, alkaline earth metal, halogen, noble gas, transition element, or inner transition element. Use an 8½ × 11” piece of paper, and fold the paper either in half or in thirds. Your child should research—using books or the Internet— the chemical family that was chosen, and include the following information in the brochure: • Names and symbols of all the elements in the family • Abundance of all elements • Melting/boiling points of elements • Uses of the elements • Any special properties of the elements • your child record the sources of the information and include pictures as appropriate. Here are some questions to discuss with your child: 1. Why did you choose the particular elemental family? 2. How are the elements in the family in which you chose similar? How are they different? 3. How are the elements within the family you chose organized on the periodic table? In other words, why are these elements included in this particular order?

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PS1BC Atomic Trends

Reading Science Name:

Date:

Group:

The Creation of the Modern Periodic Table 1

You may have already heard the name Dmitri Mendeleev, the Russian chemist who is often credited with creating the modern periodic table. While he did play a critical role in the formation of the periodic table—his original elemental table was very similar to the one we use today—he did not come to this conclusion by himself. A long history of discoveries led to Mendeleev’s creation, and there were even more discoveries after his death that led to the final version of this all-important resource. Let us recount this journey.

Almost 3,000 years ago, there were people who studied nature, known as natural philosophers, who attempted to understand how natural systems worked. Aristotle was one of these natural philosophers. In 330 BC, he deduced that all matter was made of four elements: earth, air, fire, and water. This is not quite as elementary as it may seem, as the elements that he deduced do in fact pertain to both the states of matter that we know today and the energy required to create chemical reactions.

It wasn’t until the 1700s that “modern” advancements in science began. Antoine Lavoisier is often referred to as the father of modern chemistry. Lavoisier used these types of scientific philosophies along with the scientific method to produce some groundbreaking discoveries. In the late 1700s, Lavoisier was able to make the distinction between metals and nonmetals. This would be an important distinction on the periodic table of the future. He also was able to identify and name over 30 elements. In 1789, he published the first modern chemistry textbook. This book included the first accurate definition of the law of conservation of mass, a critical concept that aids in the process of chemical analysis.

The scientific method continued as Jöns Jakob Berzelius created a table based upon the atomic weights of the known elements in 1828. In order to better recognize those elements, he gave them symbols, or letters. In 1829, a scientist named Johann Döbereiner saw patterns of elements with similar properties. He grouped elements into triads. For example, he saw that chlorine, bromine, and iodine formed a triad. (In the modern table, these elements are in the same group.) The science of chemistry continued to advance.

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PS1BC Atomic Trends

Reading Science 5

In 1864, a man named John Newlands used the 56 elements known at the time to expand on Döbereiner’s triad patterns. He saw that there were even more similarities among the elements, specifically between the first and ninth elements. He called these similarities the “law of octaves.” (In the modern table, these elements are in the same period.) He organized these elements into 11 groups based on similar characteristics.

The year 1869 was very important for the creation of the modern periodic table. In 1864, another scientist named Lothar Meyer made contributions to its early form. He developed a version of the table using the pattern of the valence electrons in 28 of the 56 known elements. Then, in 1869, he took all of this information and created a periodic table of the 56 known elements based on other elemental properties, such as atomic weight.

In this same year, 1869, Dmitri Mendeleev created his own table. Why does Mendeleev’s table receive so much credit? His table was also based on atomic weights, but it was the way that he arranged this information that made his table so valuable. He arranged the elements in a “periodic way.” This means that elements with similar properties were placed underneath each other. The elements with lower atomic weights were placed on the top row. The elements with heavier atomic weights were placed below them. This led to the first periodic table in the form we use today. There were gaps in Mendeleev’s table, but those gaps would soon be filled by future discoveries. The truly interesting thing is that as modern science was able to fill these gaps, the form of his table did not need to be altered. Mendeleev had gotten it right!

In 1894, a man named William Ramsay discovered the noble gases, which were added to the period table. In 1913, Henry Moseley calculated the atomic number of each of the known elements. He discovered that the properties of elements relied only partially on their atomic number. He found that the number of valence electrons in an atom was what actually contributed chemical properties. Even though elements are placed in the periodic table in order of increasing atomic number, it was shown that the organization of the periodic table is based on electron properties. Mendeleev’s form still held. There were two final pieces of the puzzle. In 1932, James Chadwick discovered neutrons, and in 1945, Glenn Seaborg discovered the lanthanides and actinides.

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PS1BC Atomic Trends

Reading Science 1.

Known as the father of modern chemistry, who created the first chemistry textbook? A.

Jöns Jakob Berzelius

Dmitri Mendeleev

Antoine Lavoisier

Lothar Meyer

Dmitri Mendeleev created an early version of the periodic table based on atomic mass. The modern periodic table has elements placed in increasing order of which characteristic? A.

Atomic number

Electron properties

Atomic size

The date that the element was discovered

Dmitri Mendeleev and Lothar Meyer created similar elemental tables in 1869. Why was Mendeleev’s table “more valuable” to modern science than Meyer’s table? A.

Mendeleev ordered his table in a periodic way.

Meyer did not include atomic weights.

Mendeleev used more elements.

Meyer’s table contained gaps.

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PS1BC Atomic Trends

Reading Science 4.

In 1913, a scientist named Henry Moseley discovered that the properties of elements relied partially on what? A.

Their color

Their atomic mass

The number of valence electrons

Their atomic size

Which scientist discovered that elements could be grouped into “triads,” or elements with similar properties? A.

James Chadwick

Aristotle

William Ramsay

Johann Döbereiner

A scientist named John Newlands discovered an early pattern on the periodic table regarding similarities between the first and ninth elements. What did he call this pattern? A.

The law of periodicity

The law of octaves

The law of elements

The law of trends

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PS1BC Atomic Trends

Math Connections Name:

Date:

Group:

Matter Measuring and Observing State Changes in Matter Solids, liquids, and gases have different properties that describe their state. When heat is applied to a substance, it causes the state to change, causing the properties of the substance to change as well. It can be hard to see the small particles (molecules or atoms) that make up a solid, liquid, or gas. However, we can use our observations of a substance’s volume and appearance to deduce how the particles in the substance are acting. Procedure: 1. Heat 80.0 g of ice in a 200-mL beaker. 2. Record the temperature inside the beaker every minute for 20 minutes. 3. Create a graph to describe the data you collected. Time (minutes)

Temperature (oC)

Time (minutes)

Temperature (oC)

-12

-8

-4

100

105

110

115

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PS1BC Atomic Trends

Math Connections 1.

Plot the temperature vs. time data on the graph below.

Temperature (oC)

State Changes in Matter of H2O

Time (minutes) 2.

Use a red colored pencil to create a line that represents the temperature from the start of the experiment until the ice reaches its melting point. Label the melting point with a letter A.

Describe the state of the water from 0–3 minutes. How are the water molecules spaced and what is their energy level? Describe the shape of the water and the compressibility of the molecules.

What is the equation of the line from 0–3 minutes?

Use a blue colored pencil to represent the part of the graph that shows the ice melting.

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PS1BC Atomic Trends

Math Connections 6.

What is the equation of the line that represents the ice melting?

Use an orange colored pencil to represent the water from the time it is completely melted to the time it boils and starts to evaporate. Label the boiling point with a letter B.

Describe the state of the water from 6–15 minutes. How are the water molecules spaced and what is their energy level? Describe the shape of the water and the compressibility of the molecules.

Use a green colored pencil to represent the part of the graph that shows the water boiling.

10. What is the equation of the line that represents the boiling water?

11. Are the boiling and melting points of water extensive or intensive properties?

12. Use a yellow colored pencil to represent the part of the graph from 17–20 minutes.

13. Describe the state of the water from 17–20 minutes. How are the water molecules spaced and what is their energy level? Describe the shape of the water and the compressibility of the molecules.

14. Which colors represent the phase changes from solid to liquid and from liquid to gas in your graph?

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PS1BC Atomic Trends

Writing Science Name:

Date:

LOOK

THINK The above illustration depicts an experimental setup designed to create a compound by chemically combining an iron and sulfur mixture. Students must first evaluate the intensive and extensive properties of each elements in order to determine if the mixture has in fact become chemically combined after applying heat. After preliminary examination, the students collect the following data from each element before creating the iron-sulfur mixture. Iron Malleable and solid Magnetic Gray color

Sulfur Powdered form Non-magnetic Yellow color

WRITE Using the experiment described above, explain how the examination of intensive and extensive properties of each element is essential to determining the classification of matter of a substance. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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PS1BC Atomic Trends

Writing Science Topic:

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Physical Science

PS2ABC

Ionic and Covalent Compounds

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PS2ABC Ionic and Covalent Compounds

Student Handout Name:

Date:

Household Item Chart Write down six of the chemical compounds, formulas, and common names found on the labels of the common household items. IUPAC Name

Formula

Common Name (if applicable)

Product Name

Sodium bicarbonate

Salt

Fluoride

Antiseptic

Vinegar

Ammonia

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PS2ABC Ionic and Covalent Compounds

Student Journal Name:

Date:

Group:

Background: Properties of Ionic and Covalent Bonds 1.

What is chemical nomenclature? What is the IUPAC?

_______________________________________________________________________________ _______________________________________________________________________________ 2.

What are valence electrons? What do they have to do with bonding?

What group number contains oxygen on the periodic table?

_________________________________________ 4.

How many valence electrons does oxygen have before bonding?

_________________________________________ 5.

What group number contains hydrogen on the periodic table?

_________________________________________ 6.

How many valence electrons does each hydrogen have before bonding?

_________________________________________ 7.

How many valence electrons does oxygen have after bonding?

_________________________________________ 8.

How many valence electrons does each hydrogen have after bonding?

_________________________________________ 9.

How many hydrogen and oxygen atoms does the water molecule in the diagram contain?

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PS2ABC Ionic and Covalent Compounds

Student Journal Part I: Naming and Building Ionic Bonds 1.

My question of inquiry:

Explain what ionic bonds are and how they are created.

Use your completed ionic bond puzzle pieces to complete the table below. Remember to balance the charges when writing chemical formulas. Use the first example in the table as a reference. Cation Used

Anion Used

Chemical Formula

Name of Ionic Compound

Ca+2

Cl-1

CaCl2

calcium chloride

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PS2ABC Ionic and Covalent Compounds

Student Journal Part I: Naming and Building Ionic Bonds, continued 4.

Describe how ionic charges are used in creating chemical formulas for ionic compounds. Be specific.

Describe how ionic compounds are named. What element goes first? Which element goes second?

When naming ionic compounds, what is critical to include with regard to the charges? In other words, how do you distinguish elements that may have multiple charges when naming ionic compounds? Use iron as an example.

Complete the table for naming and writing ionic compounds. Naming and Writing Ionic Compounds Compound Name

Compound Formula

sodium chloride FeBr3 mercury (II) chloride K 3N silver bromide aluminum sulfid FeO

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PS2ABC Ionic and Covalent Compounds

Student Journal Part II: Naming Rules for Covalent Bonds 1.

Explain what covalent bonds are and how they are created.

Complete the Covalent Compounds Chart. Covalent Compounds Chart

First Element

Second Element

Formula

# of First Element

# of Second Element

Name

CO2

carbon dioxide

nitrogen tribromide P205

P N

Br Cl

BCl3

diphosphorus pentoxide 2

carbon tetrafluoride

(water)

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SO3

SiO2

tetraphosphorus trisulfide

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PS2ABC Ionic and Covalent Compounds

Student Journal Part II: Naming Rules for Covalent Bonds, continued 3.

Where are the elements used to create covalent compounds found on the periodic table? What are these elements known as?

Describe the naming system used to create covalent compounds. How is the first element named? How is the second element named?

What are diatomic molecules? Name all seven of them and include their molecular formulas. Why are they diatomic?

Complete the table for naming covalent compounds. Compound Name

Compound Formula

molecular bromine

Br2

molecular fluorine carbon dioxide SO2 carbon tetrachloride N2O5 tetraphosphorus decoxide

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PS2ABC Ionic and Covalent Compounds

Student Journal Reflection and Conclusions 1.

Describe the ways in which ionic compound nomenclature differs from covalent compound nomenclature.

To understand chemical nomenclature, you must first organize your data. Briefly explain how you organized the data to understand and use chemical nomenclature. (Include ionic compounds and covalent compounds.)

Using all of the following terms, develop a graphic organizer based on what you have learned in this Explore. Use another sheet of paper, if needed.

Terms: chemical nomenclature, IUPAC, formula, chemical name, monatomic ion, ions, ionic compound, covalent compound, binary molecule, molecule, diatomic molecule, chemical formula, anion, cation, salt, electrolyte

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PS2ABC Ionic and Covalent Compounds

Student Journal Additional Practice Naming and Writing Compounds (and Identifying the Type of Bond) I.

Identify each of the following compounds as either an ionic compound or a covalent compound. Then name the compound. Use the Student Reference Sheet: Summary Chart of Naming Compounds and the periodic table. Compound Formula

Ionic or Covalent Bond

Chemical Formula

LiBr N2o3 MgS P4O10 CCl4 ZnSO4 CO SnCl2 AgI FeO BaCl2 CS2 CuBr2

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PS2ABC Ionic and Covalent Compounds

Student Journal Additional Practice Naming and Writing Compounds (and Identifying the Type of Bond), continued II.

Identify each of the following compounds with the correct IUPAC name. Common Name

Formula

water

H2O

natural gas

CH4

deicing salt

CaCl2

dry ice

CO2

muriatic acid

HCl

rust

Fe2O3

Tums

CaCO3

battery acid

H2SO4

laughing gas

N2O

table salt

NaCl

lye (a base)

NaOH

baking soda

NaHCO3

iron pyrite

FeS2

quicklime

CaO

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IUPAC Name

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PS2ABC Ionic and Covalent Compounds

Student Journal Additional Practice Naming and Writing Compounds (and Identifying the Type of Bond), continued III.

Complete the table below with the correct formula or name. Then identify the type of bond. Formula

IUPAC Name

nitrogen monoxide

Ionic of Covalent Bond

N2O NO2 N2O3 N2O4 N2O5 Cl2

molecular chlorine molecular iodine molecular hydrogen beryllium sulfide aluminum sulfide sodium fluoride barium hydroxide ammonium chloride cesium chloride potassium permanganate

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STEMscopedia: IONIC AND COVALENT

COMPOUNDS PS2ABC

Reflect Have you ever wondered why chemical compounds form and how chemical compounds get their names? What is the difference between carbon dioxide and carbon monoxide? Do you know the formula for dihydrogen monoxide?

Carbon monoxide, CO, can be deadly if too much accumulates in a poorly ventilated area.

Carbon dioxide, CO2, is breathed out by animals, taken in by plants, used in fire extinguishers, and, if frozen, becomes “dry ice.”

Chemical compounds form when atoms gain, lose, or share electrons so they may become more stable. Most atoms are stable when they have eight electrons in their outer shells. Hydrogen and helium are stable with two electrons in their electron shell. All chemical compounds, including ionic and covalent compounds, are named according to the International Union of Pure and Applied Chemistry, or IUPAC. You will use IUPAC nomenclature to name simple binary ionic and covalent compounds in this activity. Ionic Compounds An ionic compound forms when atoms bond by gaining or losing electrons. This type of compound usually forms between a metal and a nonmetal. A metal atom donates one or more electrons to a nonmetal, resulting in a positively charged ion, called a cation, and a negatively charged ion, called an anion. An ion is an atom or molecule with an electric charge. The cation and anion are joined by an ionic bond. The smallest unit of an ionic compound is called a formula unit.

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Dihydrogen monoxide is the chemical name for water or H2O. It is one of the most common substances on Earth, yet few people know its true name.

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STEMscopedia: IONIC AND COVALENT

COMPOUNDS

Metals are on the left side of the pink diagonal line and nonmetals are on the right. Metals and nonmetals join together to form ionic compounds.

A familiar ionic compound is sodium chloride, commonly known as table salt. Each formula unit of sodium chloride contains one sodium cation and one chlorine anion. The sodium atom donates one valence electron to the chlorine atom, forming the ions and the ionic bond between them. A valence electron is an electron found in the atom’s outer electron shell. Covalent Compounds A covalent compound forms when atoms bond by sharing electrons. This type of compound usually forms between two or more nonmetals. Each atom in a covalent compound shares one or more electrons with an adjacent atom, forming a covalent bond. The smallest unit of a covalent compound is called a molecule.

When a sodium atom donates an electron to a chlorine atom, it becomes a positively charged cation, and the chlorine atom becomes a negatively Identifying Ionic and Covalent Compounds charged anion. They are If you know the name of the compound, you can check the periodic held together by an ionic table to see if it contains a metal and a nonmetal, or only nonmetals. If bond. you do not know the name of the compound, you can test its properties to determine if it is ionic or covalent.

Methane, CH4, is a covalent compound. One molecule of methane contains one carbon atom and four hydrogen atoms that share electrons.

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STEMscopedia: IONIC AND COVALENT

COMPOUNDS

Most ionic compounds form crystalline solids at room temperature. The ions arrange themselves in regular, repeating patterns that form crystal shapes. Ionic compounds require very high temperatures to boil and to melt. If melted or dissolved in water, ionic compounds conduct electrical current. Covalent compounds have lower boiling and melting points than ionic compounds. Many covalent compounds are liquids or gases at room temperature and are not good conductors of electric current. Bromine is a liquid at room temperature.

Look Out Modeling Ionic and Covalent Compounds Correctly predicting chemical formulas for ionic and covalent compounds depends on knowing how many electrons are transferred or shared and how many atoms are involved. It helps to make a model of the structure of the molecule or formula unit. You can use electron dot structures (also called Lewis structures) to show the valence electrons around an atom and how the electrons are shared or transferred between two atoms. A Lewis structure for a sodium atom shows the symbol for sodium, Na, with one dot representing its one valence electron. A Lewis structure for a chlorine atom shows the symbol for chlorine, Cl, and seven dots around it to represent its valence electrons. Lewis structures can also be used to show how bonds form between some atoms. Observe in the diagram how the sodium atom transfers its one valence electron to the chlorine atom, forming ions and an ionic bond.

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STEMscopedia: IONIC AND COVALENT

COMPOUNDS

In covalent bonds, valence electrons are shared between atoms. A covalent compound, or molecule, may contain two or more atoms. In molecules with more than two atoms, one atom is the central atom. Electron pairs are placed around all atoms until each atom has or shares eight electrons. The only exception is hydrogen, which only needs one pair, or two electrons.

Sodium gives its valence electron to chlorine so it becomes a cation and chlorine becomes an anion. Together, they form an ionic bond. Notice that the ions that form are placed in brackets with their respective charges. An example of a Lewis structure of a covalent molecule is carbon tetrafluoride, CF4. The carbon atom is placed as the central atom, which is surrounded by the four fluorine atoms. Carbon has four valence electrons, so it shares one valence electron with each fluorine atom. Each fluorine atom is surrounded by seven valence electrons plus the electron it shares with carbon. Carbon shares one fluorine electron with each fluorine atom. Notice that each atom in the Lewis structure of CF4 is surrounded by eight electrons. Naming Compounds Ionic and covalent compounds are named by International Union of Pure and Applied Chemistry, or IUPAC, guidelines. There are different rules that apply to naming ionic and covalent compounds. Rules and examples for naming simple binary compounds are shown below. You will learn all the naming rules when you study chemistry. Naming Binary Ionic Compounds: • Name the cation first. • Name the anion last, but change the ending to –ide. Example: aluminum and oxygen = aluminum oxide Lewis structure for CF4.

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STEMscopedia: IONIC AND COVALENT

COMPOUNDS

Naming Binary Covalent Compounds • Name the two elements in the order their symbols appear in the formula. • Change the ending of the second element to –ide. • Add a prefix to each elemental name to denote the number of atoms of each element in the molecule. (See Table 1.) • Exception: If the first element in the molecule contains only one atom, do not use the prefix mono-. Just use its name. Examples: Prefix monoditritetrapentahexaheptaoctanonadeca-

Number of Atoms 1 2 3 4 5 6 7 8 9 10

CF4 carbon tetrafluoride CO carbon monoxide CO2 carbon dioxide P4S3 tetraphosphorus trisulfide N2O3 dinitrogen trioxide

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STEMscopedia: IONIC AND COVALENT

COMPOUNDS

What Do You Think? Compound

Ionic or Covalent?

Name of Compound

CaBr2

CCl4

P2O5

K2O Can you identify and name ionic and covalent compounds just by observing their chemical formulas? Try Now: Complete the table.

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STEMscopedia: IONIC AND COVALENT

COMPOUNDS

Connecting With Your Child Potassium Chloride Properties:

Prediction: Ionic or Covalent? Dihydrogen Monoxide Properties:

Prediction: Ionic or Covalent? Sulfur Trioxide Properties:

Prediction: Ionic or Covalent? Calcium Iodide Properties:

Prediction: Ionic or Covalent? Use the Internet to research the properties of these compounds. Based on their properties, predict whether they are ionic or covalent.

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PS2ABC Ionic and Covalent Compounds

Reading Science Name:

Date:

Group:

IUPAC 1

Chemical formulas describe how atoms combine to form every compound that composes matter. Just like any language, the way that elements combine follows very specific rules. As you may know, each element has a unique chemical symbol and a characteristic number of valence electrons. Elements combine in very predictable patterns, but with a huge number of possible variations. How does everyone agree about how to name the compounds that can be created with the 118 known elements? Very specific rules have been created by a standardizing organization called IUPAC, the International Union of Pure and Applied Chemistry. What is this organization? How did it decide upon these rules?

The ancients knew about elements such as gold and silver more than 1,000 years ago. However, it was not until the mid-1700s that scientists began to isolate and identify other elements. By the mid-1800s, there were 62 known elements that needed to be named and categorized. These elements were identified by the differences in their properties and masses. They were also characterized by the ways that they combined with other known elements. These elements were given names by the scientists who discovered them. However, there was not a standardized system to categorize and make use of these elements. How could scientists use what they had learned about their discoveries in a meaningful way?

In 1860, German scientist Friedrich August Kekulé von Stradonitz led a committee to discuss these very issues. During this meeting, the committee members decided upon the first international system to name the known elements and compounds. This was especially important because of the ever-growing number of discoveries. The scientific community needed to know that, when discussing a chemical, they were all referring to the same element or compound. Scientists also needed to be given the proper credit for their studies.

However, it was soon found that the system set by the 1860 committee needed to be modified. New elements were being discovered. The number of known compounds was also rapidly growing. As more and more scientists performed experiments with these chemicals, there became a growing confusion about how to name and categorize them. In 1892, a new committee called the International Union of Chemistry (IUC) met to create and reform even more rules. These rules became known as the Geneva rules. The rules set forth by the IUC became the fundamental standardized rules for all organic compounds.

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PS2ABC Ionic and Covalent Compounds

Reading Science 5

In 1911, there was another meeting. This was called the International Association of Chemical Societies (IACS). This committee met in Paris, France, to discuss exactly what types of processes the society should address. The final decision included authority over several processes. IACS would oversee the naming (nomenclature) of both inorganic and organic chemicals. It would determine procedures for standardizing the atomic weights of newly and previously discovered elements. IACS would create and maintain tables identifying the physical and chemical properties of elements and compounds. They would also create commissions to review scientific work and standardize both scientific publications and discoveries.

Finally, in 1919, the International Union of Pure and Applied Chemistry was created to follow both the IUC and the IACS. IUPAC has become a very influential organization. IUPAC oversees all chemical nomenclature in the world. Currently, the headquarters of IUPAC is located in Zürich, Switzerland. They have administrative offices in North Carolina known as the IUPAC Secretariat. IUPAC consists of many committees, all with varying responsibilities. Each committee is responsible for a different project and for the regulation of their nomenclature field. All of IUPAC’s decisions are built upon the work and regulations of the previous unions and societies. The following is the current mission statement of IUPAC:

“The International Union of Pure and Applied Chemistry (IUPAC) serves to advance the worldwide aspects of the chemical sciences and to contribute to the application of chemistry in the service of Humankind. As a scientific, international, non-governmental, and objective body, IUPAC can address many global issues involving the chemical sciences.”

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PS2ABC Ionic and Covalent Compounds

Reading Science 1.

The field of chemistry had incredible advancements in a very short time period, from the mid1800s to the early 1900s. It was during this time period that the scientific community saw the need for the regulation of the growing number of chemical discoveries. What were the early committees trying to regulate? A.

Who actually discovered each chemical or element

How the newly discovered elements were named

How the chemical discoveries were published

All of the above

The International Union of Chemistry (IUC) developed a specific set of rules for chemists to follow. What were these rules called? A.

The nomenclature rules

The IUC rules

The Geneva rules

The Paris rules

Which committee stated has the below mission statement?“[This committee] serves to advance the worldwide aspects of the chemical sciences and to contribute to the application of chemistry in the service of Humankind. As a scientific, international, non-governmental, and objective body, [this committee] can address many global issues involving the chemical sciences.” A.

IUPAC

IUC

IACS

None of the above

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PS2ABC Ionic and Covalent Compounds

Reading Science 4.

The International Association of Chemical Societies was created to make sure certain chemical processes and standards were followed. Which of the following was not one of those standards? A.

The standardization of the atomic weights of newly and previously discovered elements

The regulation of the IUPAC Secretariat office in North Carolina

The naming (nomenclature) of both inorganic and organic chemicals

The creation and maintenance of tables identifying the physical and chemical properties of elements and compounds

The number of known elements changed very rapidly over a 150-year period. There were 62 known elements in the mid-1800s. How many known elements (total) are there today? A.

The standardization of the atomic weights of newly and previously discovered elements

The regulation of the IUPAC Secretariat office in North Carolina

The naming (nomenclature) of both inorganic and organic chemicals

The creation and maintenance of tables identifying the physical and chemical properties of elements and compounds

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PS2ABC Ionic and Covalent Compounds

Math Connections Name:

Date:

Group:

Chemical Formulas Part I: Naming Ionic Compounds

The following table lists most of the ionic formulas you will need. The charge on other positive ions will be indicated by a roman numeral. Use your periodic table for elements not shown on the chart. Name Aluminum ion Ammonium ion Calcium ion Lithium ion Potassium ion Silver ion Iron ion Barium ion Magnesium ion Chromium ion 1. 2. 3. 4.

Formula Name Formula Name Formula 3+ Bromide ion Br Carbonate ion CO32Al NH4+ Chloride ion ClHypochlorite ion ClOCa2+ Fluoride ion FChromate ion CrO42Li+ Iodide ion IHydroxide ion OHK+ Nitride ion N3Nitrate ion NO3Ag+ Oxide ion O2Phosphate ion PO43Fe+ Sulfide ion S2Sulfate ion SO42Ba2+ Phosphide ion P3Bisulfate ion HSO4Mg2+ Perchlorate ion ClO4Cr3+ Steps to Naming Chemical Compounds List the symbols for each ion. Write the symbols for the ions, side-by-side, with the cation first. Find the least common multiple of the ions’ charges. Write the chemical formula, using subscripts, to indicate how many of each ion are needed to make a neutral compound.

Give systematic names for the following compounds: a)

BaCl2

CrCl3

PbS

d) Fe2O3 Write the formulas for the following compounds: e)

Magnesium fluoride

Tin (IV) oxide

Iron (III) sulfide

Manganese (IV) oxide

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PS2ABC Ionic and Covalent Compounds

Math Connections Part II: Naming Molecular Binary Compounds

Molecular compounds combine through covalent bonds and are named differently than ionic compounds. The number of atoms of each element is described using a prefix like mono-, di-, tri-, tetra-, penta-, or hexa-. However, if the first element has only one atom, mono- is not used; the element is simply named. (Example: NO is nitrogen monoxide.) 3.

Give systematic names for the following compounds: a)

PCl3

N2O3

BrF3

NCl3

Write the formulas for the following molecular compounds: a)

Disulfur dichloride

Iodine monochloride

Nitrogen triiodide

Part III: Naming Compounds with Polyatomic Ions

Polyatomic ions are charged ions composed of two or more atoms covalently bonded. Identify the polyatomic ion from the chart on the first page. To name the compound, list the cation first and then name the polyatomic ion. 5.

Give systematic names for the following compounds: a)

LiNO3

KHSO4

CuCO3

Fe(ClO4)3

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PS2ABC Ionic and Covalent Compounds

Math Connections Part III: Naming Compounds with Polyatomic Ions, continued 6.

Write formulas for the following compounds: a)

Potassium hypochlorite

Silver (I) chromate

Iron (III) carbonate

Part IV: Writing Ionic Formulas 7.

Thiosulfate (S2O32-) is an ion of sulfur and occurs naturally in hot springs and geysers. Ammonium thiosulfate is used to make fungicide, barium thiosulfate is used in the manufacturing of explosives, and potassium thiosulfate is used in the photo development process. Write the chemical formulas for these three compounds.

Iron pyrite, or fool’s gold, is the most common sulfide mineral. It is used in the manufacturing of iron (II) sulfate commonly used to treat iron deficiency in humans. Write the chemical formula for iron sulfate.

Mercury, used in thermometers, is obtained by heating cinnabar ore, or mercury (II) sulfide. Write the ionic formula for mercury (II) sulfide.

10. Arsenic (III) chloride is a poisonous, colorless oil. It is used to make pharmaceutical compounds, pesticides, and ceramics. Write the ionic formula for arsenic trichloride.

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PS2ABC Iconic and Covalent Compounds

Writing Science Name:

Date:

LOOK

THINK Naming and writing chemical formulas varies according to the type of compounds that are involved. To insure consistency among scientists, the International Union of Pure and Applied Chemistry (IUPAC) devised several rules of nomenclature. While all nations practice science, they don’t always speak the same language. In order to produce a better way to communicate globally in terms of science, it was inevitable that a common language would have to be established. The IUPAC devised several detailed rules of nomenclature which helped to bridge this language divide. The purpose of this nomenclature is also to name each chemical in a way that leaves no ambiguity and clearly describes the chemical structure of the compound while arriving at a single name. Between language differences and common names, it is a necessity to have a common set of rules for nomenclature in order to correctly identify compounds. For example: The IUPAC nomenclature varies depending on the type of compound being named. WRITE Common Name Battery acid Lye Baking soda

Chemical Formula H2SO4 NaOH NaHCO3

IUPAC Name Sulfuric acid Sodium hydroxide Sodium hydrogen carbonate

Compare the IUPAC nomenclature rules for naming acids and bases. Provide common examples of each to support your statements. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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PS2ABC Iconic and Covalent Compounds

Writing Science Topic:

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Physical Science

PS3AB

Conservation of Mass During Chemical Reactions

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PS3AB Conservation of Mass During Chemical Reactions

Student Handout Name:

Date:

The law of conservation of mass states that matter cannot be created or destroyed in an ordinary chemical reaction. This means that the amount of matter you end up with in a chemical reaction must be equal to the amount you started with. This experiment will test this law to see if it is really true. Physical Properties Reactants

Products

effervescent tablet

water

Observing the Mass Mass before the reaction in grams

Total mass of reactants + graduated cylinder + balloon

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Mass after the reaction in grams

Total mass of products + graduated cylinder + balloon

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PS3AB Conservation of Mass During Chemical Reactions

Student Handout Conclusions: 1.

Did a chemical reaction take place? How do you know?

What happened to the balloon after you added the effervescent tablet to the water? Why?

Compare the mass of the graduated cylinder setup before and after the effervescent tablet and water were combined. Was there a difference? If so, what might have caused this? If not, why not?

Does this reaction uphold the law of conservation of mass? Why or why not?

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PS3AB Conservation of Mass During Chemical Reactions

Student Journal Name:

Date:

Group:

Part I: The Big Picture 1.

What are the starting substances (molecules) in a chemical equation called?

_______________________________________________________________________________ 2. What are the final, or new, substances (molecules) in a chemical equation called? _______________________________________________________________________________ 3.

In your own words, describe what happens to the hydrogen and oxygen molecules when forming water. Something must be recombined. How does this happen?

Part II: Chemical Formulas Chemical Formula

ZnCl2

NaCl

CuCl2

MgCl2

CO2

Elements and Number of Atoms

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Model

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PS3AB Conservation of Mass During Chemical Reactions

Student Journal Part III: Chemical Equations 2FeO → 2Fe + O2 Reactants

Products

Model of Reactants

Model of Products

2CU + O2 → 2CuO Reactants

Products

Model of Reactants

Model of Products

2Na + 2HCl → H2 + 2NaCl Reactants

Products

Model of Reactants

Model of Products

Cl2 + 2Kl → 2KCl + I2 Reactants

Products

Model of Reactants

Model of Products

Mg + 2HCl → MgCl2 +H2 Reactants

Products

Model of Reactants

Model of Products

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PS3AB Conservation of Mass During Chemical Reactions

Student Journal Part III: Chemical Equations, continued 1.

What happens to the reactant molecules when forming product molecules?

_______________________________________________________________________________ _______________________________________________________________________________ 2.

What do the coefficients that are located before certain molecules in each chemical equation represent?

_______________________________________________________________________________ _______________________________________________________________________________ 3.

What do you notice about the elements on the reactant and product side of the equation?

What do you notice about the number of atoms of each element on the reactant and product side of the equation?

Part IV: The Balancing Act Zn + HCl → ZNCl2+H2 Reactants

Products

Model of Reactants

Model of Products

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PS3AB Conservation of Mass During Chemical Reactions

Student Journal Part IV: The Balancing Act, continued Look at the chemical equations below. Determine which of these equations is balanced and which is not. First identify the type and number of atoms found on the reactant and product side of the equation, and then circle whether the equation is Balanced or Not Balanced.

2Na + O2 → Na2O

Balanced

Not Balanced

Ni2O3 → Ni + O2 Balanced

Not Balanced

2Al + 3Cl2 → AlCl3

Balanced

Not Balanced

2P + 3I2 → 2PI3 Balanced

Not Balanced

H2O2 → 2H2O + O2

Balanced

Not Balanced

2HCl + CuO → CuCl2 + H2O

Balanced

Not Balanced

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PS3AB Conservation of Mass During Chemical Reactions

Student Journal Part V: Types of Chemical Reactions 1.

Look at the balanced equations listed below. Decide what type of reaction each equation represents. Balanced Chemical Equation 1

3Mg + N2 → Mg3N2

Zn + 2HCl → ZnCl2 + H2

2H2O2 → 2H2O + O2

2KF + MgBr2 → MgF2 + 2KBr

2Al2O3 → 4Al + 3O2

2NaCl + F2 → 2NaF + Cl2

3H2 + N2 → 2NH3

CH4 + 2O2 → CO2 + 2H2O

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Type of Reaction

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PS3AB Conservation of Mass During Chemical Reactions

Student Journal Reflections and Conclusions 1.

In your own words, explain what the law of conservation mass tells us.

_______________________________________________________________________________ _______________________________________________________________________________ 2. Why is the law of conservation mass important to understand when writing chemical formulas and chemical equations? _______________________________________________________________________________ _______________________________________________________________________________ Use the chemical equation below and all of the information learned in this Explore activity to answer the questions below.

CuO + 2HCl → CuCl2 + H2O 3.

Write down the chemical formulas of the reactants. State how many atoms of each element are on the reactant side.

Write down the chemical formulas of the products. State how many atoms of each element are on the product side.

_______________________________________________________________________________ _______________________________________________________________________________ 5. How does the number of atoms present on each equation side relate to the law of conservation mass? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 6. Name the four different types of chemical reactions and what is happening in each one. A.

___________________________________________________________________________ ___________________________________________________________________________

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DURING CHEMICAL REACTIONS

Reflect

PS3AB

Have you ever watched a chemical reaction occur and wondered what happened to the original substance? Was something new created? Did the original matter disappear? Where did it go? Important vocabulary to know: Reactants: In a chemical equation, the reactants, which are the starting substances, are usually written on the left side of the equation.

Products: The products of the reaction are the substances that result from the reaction. Products are usually written on the right side of the equation.

Evidence That Mass Is Conserved During a Chemical Reaction If you mix baking soda with vinegar, you start with a powder and a liquid. When the reactants (baking soda and vinegar) react, you end up with a product that consists of a liquid and a gas. If you measure the mass of the baking soda and vinegar before the reaction and then measure the mass of the product after the reaction (in a closed system), you will find that the total mass of the reactant was equal to the total mass of the product. How does this happen? The law of conservation of mass states that, in any chemical reaction, the total mass of the reactants is always equal to the mass of the products. Matter can neither be created nor destroyed, but the atoms that make up that matter can be rearranged and also change states of matter. Apply the concept of the law of conservation of mass to the following question.

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DURING CHEMICAL REACTIONS

A glass of unsweetened lemonade has a mass of 255 grams. A spoonful of sugar is massed before stirring it into the lemonade. The sugar has a mass of 25 grams. Predict how much mass you think the sweetened lemonade will have after you stir in the sugar. 1. It will have a mass of slightly less than 255 grams but more than 230 grams. 2. It will have a mass of slightly more than 255 grams but less than 280 grams. 3. It will have a mass of 230 grams. 4. It will have a mass of 280 grams. 5. It will have the same mass of 255 grams. Chemical formulas describe atoms held together by chemical bonds.

A compound is a group of atoms of different elements joined together by sharing or transferring electrons. The atoms are then held together by a chemical attraction, called a bond. During a reaction, these bonds can be broken so new bonds can be formed. This is why our product doesn’t always look like the reactant after the chemical reaction.

Using a Model of a Chemical Equation to Illustrate How the Total Number of Atoms Is Conserved During a Chemical Reaction

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Compare the shapes of the reactant side to those on the product side. What do you notice? You will see that there is the same number of each shape on both sides of the equation. This means that the equation is balanced. During this chemical reaction, the atoms (each shape) were rearranged, but none were created or destroyed.

Look Out When balancing equations, remember that the subscript (the little number after the atom) represents the number of atoms that are present during a chemical reaction. The coefficient (the large number in front of the molecule) describes the number of molecules of each substance that is present during the reaction. The coefficient can be changed in order to balance the equation, but the subscript cannot be changed to balance the chemical reaction. Let’s Recap: To balance an equation, you need to write numbers called _________________________________ in front of the molecule or compound. DO NOT CHANGE THE SUBSCRIPTS!

What Do You Think? Let’s Practice: Write a word equation Write the given mass for each substance

Hydrogen + Oxygen 4g

Water

Use the LCM (reactants = products)

4 + ?? = 36

Solve to find the missing value

?? = 36 – 4 ?? = 32 So 32 grams of oxygen were used

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36 g

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Example #1: Some potassium oxide was placed in 9 grams of water, and 112 grams of potassium hydroxide were made. What mass of potassium oxide was used? Write a word equation Write the given mass for each substance

Potassium Oxide + Water ??

Potassium Hydroxide

112 g

Use the LCM (reactants = products) Solve to find the missing value ________________________________________ grams of potassium oxide were used. Example #2: When 245 grams of potassium chlorate are heated, the potassium chlorate breaks down into 71 grams of chlorine, 78 grams of potassium and some oxygen gas. What is the mass of oxygen formed? Write a word equation Write the given mass for each substance Use the LCM (reactants = products) Solve to find the missing value _______________________________________ grams of oxygen gas were formed.

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DURING CHEMICAL REACTIONS

Connecting With Your Child Discussion: The law of conservation of mass states that matter can neither be created nor destroyed; it can only be transferred from state to state. Use the following activity to prove this! Here are the substances that you will be working with during this experiment: Baking Soda (sodium Bicarbonate) + Vinegar Water NaHCO3 + HC2H3O2

(Acetic Acid) Sodium Acetate + Carbon Dioxide + NaC2H3O2 + H2O + CO2

List the reactants: _____________________________________ List the products: ______________________________________ Materials: Vinegar 1 small cup Pipette or dropper 2 teaspoons baking soda Balance/scale that measures in grams Ziploc bag Procedure: 1. Measure out two teaspoons of baking soda and place it into the plastic bag. 2. Fill the cup with four full squirts of vinegar from the pipette. 3. Place the cup of vinegar in the plastic bag with the baking soda, but be careful NOT to spill the vinegar. 4. Seal the plastic bag. 5. Determine the mass of the bag, baking soda, vinegar, and cup. Record this initial mass in the data table below. 6. Without opening the bag, pour the vinegar into the baking soda. 7. Observe 8. Now record the mass of the bag and contents WITHOUT opening the bag. Record the final mass in the data table below. 9. Complete the Change in Mass section of the data table below.

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STEMscopedia: CONSERVATION OF MASS

DURING CHEMICAL REACTIONS

Data Table Initial Mass (g)

Final Mass (g)

Change in Mass (g) Final Mass – Initial Mass

Analysis Questions: 1. Describe what happened when the vinegar was poured into the baking soda. 2. What is the law of conservation of mass, and how does it relate to this lab? 3. Why did we do this experiment in a plastic bag? Let’s take it a step further! This lab showed one example of the law of conservation of mass. Design an experiment with a different procedure to show this law using an effervescent tablet and water.

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PS3AB Conservation of Mass During Chemical Reactions

Reading Science Name:

Date:

Group:

Law of Conservation of Mass 1

Chemical reactions are occurring both inside of us and all around us, every second of every day. As a matter of fact, there is never a time when some type of chemical reaction is not occurring. In these processes, the starting chemical compounds (reactants) are destroyed, and new chemical compounds (products) are created. However, during all of these trillions of chemical reactions that occur each and every day, matter is neither destroyed nor created. What does this mean? Didn’t you just read that compounds are destroyed and new compounds are made during each chemical reaction? Yes, this is true, but during the chemical reactions, the total mass of the chemicals that reacted will always equal the total mass of the products created. This is the fundamental definition of a law that governs all chemical reactions, called the law of conservation of mass.

Simply stated, the definition of the law of conservation of mass is the following: mass is conserved and is neither created nor destroyed in a non-nuclear change. The total mass of the reactants equals the total mass of the products. The graphic on this page illustrates this point. In the balanced chemical equation, there is the same number of hydrogen and oxygen atoms on both sides of the equation. Matter was neither created nor destroyed during the reaction; it simply changed forms.

So how did early chemists discover that mass was neither created nor destroyed? The earliest Greek natural philosophers postulated that “nothing comes from nothing.” They knew that matter did not spontaneously appear, but they could not yet fully explain how or why it changed forms. From these early times, scientists used experiments and their keen powers of observation to try to answer these questions. Many early scientists, known at the time as alchemists, worked with various elements and combined them to investigate what was produced.

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PS3AB Conservation of Mass During Chemical Reactions

Reading Science 4

However, the conservation of mass was difficult for early scientists to conceptualize, as many of the gases required for or produced during chemical reactions were difficult, if not impossible, to quantify and measure. The gases were invisible in most cases and would either come from or escape back into the atmosphere. A classic example of this dilemma occurred with the burning of wood. As the product ash has less mass than the reactant wood, it seemed that mass was lost. It was not until experiments were conducted in sealed containers that scientists began to understand that during chemical reactions, the masses of the starting and ending substances did not change. In other words, scientists began to understand that during chemical reactions, mass was “conserved.” This concept was pivotal in the process that changed the study of alchemy into what we know as modern chemistry.

One of these early and influential modern chemists was Antoine Lavoisier (1743-1794), who is credited with being the first to discover the principle of mass conservation. His experiments were a continuation of the work of Henry Cavendish (1731-1810), who discovered the element hydrogen (although he did not name it at the time.) During his experiments, Cavendish discovered what he called inflammable air (hydrogen) and found that this substance formed water as a byproduct of combustion. At the time, both water and air were considered elements. Lavoisier wanted to better understand what “water” and “air” were made of, so he conducted very meticulous quantitative experiments. He was careful to measure the masses of both the reactants and products of the chemical reactions that he was working with. Due to his precise measurements, he concluded that although the matter may have changed forms during the reaction, no mass was lost. As a result of his experiments, Lavoisier identified and named the elements hydrogen and oxygen, and he subsequently became known as the father of modern chemistry.

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Reading Science 1.

The law of conservation of mass tells us, in part, that matter is neither created nor destroyed. How can the law of conservation of mass for a chemical reaction be expressed? A.

By using coefficients in a chemical equation

By writing a balanced chemical equation

By counting the atoms present on each side of the equation

All of the above

Early chemists, known at the time as alchemists, had a difficult time understanding the law of conservation of mass. Using the burning of wood as an example, what property of matter made this law difficult for early scientists to understand? A.

Wood is heavier than ash.

The fire was too bright to observe the reaction.

The gases produced escaped to the atmosphere.

Different types of wood burned differently.

Is there something wrong with the chemical equation below? Look carefully at this equation. CH4 + O2 CO2 + H2O. What would need to be done to this equation to make sure that it follows the law of conservation of mass? A.

Remove two hydrogen atoms (reactant) and one oxygen atom (product).

Add coefficients to some of the compounds to balance the number of atoms.

Add two hydrogen atoms (product) and one oxygen atom (reactant).

This equation already follows the law of conservation of mass.

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Reading Science 4.

Early scientists performed experiments regarding mass and products for many years, but they had difficulty demonstrating that mass was conserved. This changed when they conducted these experiments under which of the following specific conditions? A.

They conducted experiments with specific gases.

They conducted experiments with specific types of wood.

They created scales that gave more precise measurements.

The experiments were conducted in sealed containers.

Many scientists worked to explain how matter and mass were connected in the process of chemical reactions. One scientist stands out with regards to the law of conservation of mass and is often referred to as the father of modern chemistry. Who is this scientist? A.

Albert Einstein

Henry Cavendish

Antoine Lavoisier

Amedeo Avogadro

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PS3AB Conservation of Mass During Chemical Reactions

Reading Science 6.

Balanced chemical equations follow the law of conservation of mass, as these types of reactions will contain the same number of atoms of each element on the reactant side and the product side. I. CH4 + O2

CO2 + 2 H2O

II. Na + 2 H2O III. CaCO3

H2 + 2 NaOH CaO + CO2

IV. 2 Al + 3 Cl2 V. P + 2 O2

2 AlCl3 2 P2O3

Which of the chemical reactions shown above are correctly balanced? A.

I, II, and V

III and IV

II and IV

I, III, and V

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PS3AB Conservation of Mass During Chemical Reactions

Math Connections Name:

Date:

Group:

Chemical Equations In a chemical change, bonding between atoms changes and new substances are formed as a result. The law of conservation of mass states that the number and type of atoms in the reactants are exactly equal to the number and types of atoms in the products. The total mass of the reactants vs. the products is also equal. Chemical equations are used to describe reactions and the way atoms combine with one another to form new molecules. Use a periodic table to assist you in solving the following problems. 1.

Fermentation is a process that occurs when making bread dough. Write the balanced equation for the fermentation of sugar to yield ethyl alcohol. Unbalanced Equation: C6H12O6

C2H6O + CO2

Step 1: Balance the hydrogen atoms. Step 2: Balance the carbon atoms. Step 3: Balance the oxygen atoms. Balanced Equation: ___________________________________ 2.

Hydrazine is a component of rocket fuel. Balance the equation for the synthesis of hydrazine. Unbalanced Equation: NH3 + Cl2

N2H4 + NH4Cl

Step 1: Balance the chlorine atoms. Step 2: Balance the hydrogen atoms. Step 3: Balance the nitrogen atoms. Balanced Equation: ____________________________________

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Math Connections 3.

Propane is a gas used for cooking on gas grills. When propane mixes with oxygen, it forms an exothermic reaction resulting in carbon dioxide and water. Balance the equation. C3H8 + O2

CO2 + H2O

Plants and some unicellular organisms use photosynthesis to make food. Balance the equation for photosynthesis. CO2 + H2O

C6H12O6 + O2

Potassium chlorate, an ingredient in matches, reacts with sugar (sucrose) in an exothermic reaction yielding potassium chloride, carbon dioxide, and water. Write a balanced equation for the reaction. KClO3 + C12H22O11

KCl + CO2 + H2O

Which of the following equations are balanced? a)

The development reaction in photography: 2AgBr + 2NaOH + C6H6O2

2Ag + H2O + 2NaBr + C6H4O2

The preparation of household bleach: 2NaOH + Cl2

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NaOCl + NaCl + H2O

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PS3AB Conservation of Mass During Chemical Reactions

Math Connections The law of conservation of mass states that matter cannot be created nor destroyed; therefore, the mass of the products in a chemical reaction is always equal to the mass of the reactants. Even when matter changes state, mass is conserved. 7.

In the reaction to create silver sulfide, silver reacts with sulfur as described by the following equation: 2Ag + S Ag2S. If 215.8 g of silver is mixed with 32.1 g of sulfide, how much silver sulfide (in grams) will be produced? Use equations to help you solve for the answer.

Iron oxide, known as hematite, is the main source of iron for the steel industry. It is created when iron and oxygen combine in a thermal decomposition reaction. It can be described using the equation 4Fe + 3O2 2Fe2O3. If 19.2 g of O2 reacts with iron to form 63.84 g of iron oxide, how much iron in grams was used in the reaction? Use equations to help you solve for the answer.

Acetylene gas (C2H2) is used in welding torches. When it reacts with oxygen, it produces carbon dioxide (CO2) and steam (H2O). The reaction can be described by the equation: 2C2H2 + 5O2 4CO2 + 2H2O. How much mass of C2H2 is needed to react with 68.1 g of O2 to produce 75.0 g of CO2 and 15.35 g of steam?

10. In the combustion reaction 2C2H6 +7O2 4CO2 + 6H2O, ethane gas reacts with oxygen to produce carbon dioxide and steam. If 18.6 g of C2H2 reacts with 69.2 g of O2 to produce 54.4 g of CO2, how much steam does it produce?

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PS3AB Conservation of Mass During Chemical Reactions

Writing Science Name:

Date:

LOOK

CH + O 4

CO + H O

unbalanced

CH + 2O CO + 2H O 4

balanced

THINK Compare the two chemical equations. How was the unbalanced equation modified to follow the Law of Conservation of Mass and become balanced? Chemical equations are a graphic representation of an actual chemical reaction. The chemical formulas stand in place for the reactants and products that are used or produced during a chemical reaction. A chemical equation not only shows which reactants and products that are in place during a chemical reaction, but it also shows the quantities required for each. The quantities of a reactant or a product are represented by a large number in front of each chemical formula called a coefficient. Only the coefficients can be modified while writing a chemical equation. The modification of the coefficient represents a change in only the number of molecules or moles reacted or produced in the chemical reaction. The small numbers or subscripts found in chemical formulas are never to be modified. The modification of a subscript would change the chemical formula, creating a reactant or product that is not actually present in the chemical reaction. A chemical equation follows the Law of Conservation of Mass, or is said to be balanced, when the number of atoms on the reactant side equal the same number of atoms found on the product side. WRITE Explain how the chemical reaction above had to be manipulated in order to follow the Law of Conservation of Mass. Why were only the large numbers (coefficients) changed, but not the small numbers (subscripts)? Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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PS3AB Conservation of Mass During Chemical Reactions

Writing Science Topic:

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Physical Science

PS4AB

Fission, Fusion, and Radioactive Decay

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PS4AB Fission, Fusion, and Radioactive Decay

Student Journal Name:

Date:

Group:

Part I: Model It! Fusion 1.

Draw and label your two nucleus models below. Deuterium

Tritium

How are these two models different?

_______________________________________________________________________________ _______________________________________________________________________________ 3. How is it possible for both of these to be hydrogen? _______________________________________________________________________________ _______________________________________________________________________________ 4. What element does your nucleus represent now? How do you know? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 5. Draw and label your model after you joined together the deuterium and tritium nuclei, and then remove one neutron.

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PS4AB Fission, Fusion, and Radioactive Decay

Student Journal Part II: Model It! Fission 1.

Draw the classes massive, unstable nucleus. You do not have to draw every single proton and neutron. However, make sure to show that the nucleus is much larger than the one(s) from Part I.

Explain what happened when your teacher finished the activity.

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PS4AB Fission, Fusion, and Radioactive Decay

Student Journal Part III: Radioactivity Complete the data table as your candy isotopes decay. Trial

Number of Radioactive Atoms

Number of Stable Atoms

2. Complete the class data table. Number of Atoms That Decayed (Became Stable) Group

Trial 1

Trial 2

Trial 3

Trial 4

Trial 5

Trial 6

Trial 7

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PS4AB Fission, Fusion, and Radioactive Decay

Student Journal Part III: Radioactivity, continued 3.

What was the half-life of your radioactive sample? Remember, this is the time it takes for half of the sample to decay. Record your answer by trial number. Explain how you got your answer.

Reflections and Conclusions 1.

Why would the fusion model from Part I have been incorrect if you had not removed one neutron? How do you know?

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STEMscopedia: FISSION, FUSION, AND

RADIOACTIVE DECAY

Reflect

PS4AB

Energy is a hot debate topic these days. Many people want to switch from using fossil fuels, such as oil and natural gas, to other energy sources that do not release carbon dioxide into the atmosphere. They are concerned about the effects of carbon dioxide on climate change. This concern has prompted interest in increasing the number of nuclear power plants. Nuclear power plants do not produce carbon dioxide, but their operation is associated with many risks. That puts society in a bind. Should nuclear power be used as a source of energy or not? The answer to this question is not easy. In order to address it, we must ﬁrst answer other questions. What takes place in nuclear reactions? What risks are associated with these reactions when they are used in nuclear power plants?

White clouds of steam are released from the cooling towers of an operating nuclear power plant.

Nuclear Reactions: Changes in the Nucleus of an Atom When we think about chemistry, we tend to focus on changes that occur as electrons are traded or shared between atoms during chemical reactions. During these changes, the nuclei of atoms do not participate. Only electrons are involved as one set of chemical bonds is broken and a new set of bonds is formed. However, another category of reaction involves changes in atomic nuclei. As such, they are called nuclear reactions. Nuclear chemistry is the branch of chemistry that deals with the properties and reactions of atomic nuclei. Nuclear Decay There are several types of nuclear reactions. In this section, we will focus on nuclear decay. These reactions occur when an atomic nucleus is unstable. To achieve stability, this unstable nucleus decays, or partially disintegrates. The type of decay depends on the makeup of an atom’s nucleus. Every element is deﬁned by the number of protons in the nucleus of an atom of that element. However, atoms of the same element can have different numbers of neutrons in their nuclei. This variation in neutron number gives rise to different isotopes of an element. For example, all helium atoms have two protons in their nuclei, yet they A radioactive atom has an can have one or two neutrons. These two isotopes of helium are unstable nucleus. When the illustrated below. nucleus decays, it releases mass (often in the form of particles) and energy. We call this radiation.

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RADIOACTIVE DECAY

Notice the symbols used to represent the isotopes. The element’s mass number is written at the upper left of the atomic symbol. This indicates the number of protons and neutrons in the atom’s nucleus. The atomic number is written at the lower left of the atomic symbol. This is the number of protons in the nucleus. Isotopes have the same Some isotopes of an element tend to be more stable than others. number of protons but differ Radioisotopes are isotopes with unstable nuclei that tend to undergo in numbers of neutrons. decay. Often the instability results from having too many or too few This diagram shows both neutrons. To achieve stability, a radioisotope releases particles, highisotopes of helium (He). energy photons, or a combination of the two. Radiation is the term used to describe these types of emissions. Let’s look at some specific examples. •

•

Alpha radiation: Many radioisotopes emit alpha radiation. The example on the right is a good example of alpha radiation. The nucleus in an atom of plutonium-240 contains 94 protons and 146 neutrons. Therefore, its atomic mass is 240 (94 + 146 = 240). This nucleus is unstable and disintegrates by releasing an alpha particle. This particle, often represented by the Greek letter α (alpha), is composed of two protons and two neutrons, and it carries a +2 charge. This is the composition of a helium-4 nucleus. What is left of the plutonium-240 nucleus that underwent decay? As a result of the decay, it lost two protons and two neutrons. Because it has lost protons, its elemental identification has changed. The result is an atom of uranium with 92 protons and 144 neutrons. Beta radiation: Beta emission involves another type of particle emitted by a decaying nucleus. Many beta particles are electrons, particles that are much smaller than alpha particles and carry a -1 charge. They are represented by the Greek letter beta (β). Carbon-14 is a radioisotope that emits beta particles when it decays. During each decay event, a neutron in the carbon-14 nucleus breaks down to form a proton and a beta particle. The beta particle is released into the environment, while the proton remains in the nucleus. This added proton changes the atom’s identity from carbon with six protons to nitrogen with seven protons. Gamma radiation: The nuclear decay that results in the emission of alpha or beta particles can leave a nucleus with excess energy. The nucleus can release this energy as gamma radiation. Gamma rays are represented by the Greek letter gamma (γ). This type of radiation consists of high-energy photons with no mass and no charge. Because these photons have no mass, their emission does not change the balance of protons and neutrons in a nucleus. For example, when cobalt-60 undergoes radioactive decay, both beta particles and gamma rays are released.

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These three types of radiation are hazardous to humans because they can damage living cells. Each type of radiation is characterized by a different energy and ability to penetrate matter. Alpha radiation is weakest. It cannot penetrate the thick layer of skin cells of the human body, though it is dangerous if ingested. Beta radiation is energetic enough to pass through human skin cells and damage living tissue. A thin layer of aluminum metal can stop beta radiation. People working with beta emitters need to wear protective clothing to shield themselves from beta emissions. Gamma radiation is the most energetic of all. It is extremely hazardous because of its ability to penetrate most types of matter. Thick lead boxes must be used to contain radioisotopes that emit gamma radiation. Alpha, beta, and gamma radiation each has a different penetrating power.

Radiation Decay: Half-Life Alpha, beta, and gamma are different forms of radiation. Scientists use the term half-life to refer to the actual time it takes half of a given substance to decay. The example to the right shows C-14 going through radiation decay to form nitrogen-14. Scientists have determined that the half-life of carbon-14 is 5,740 years. Below is an example of carbon-14’s half-life. If you start with 10 grams of carbon-14, after 5,740 years, half of the carbon-14 will be decayed into nitrogen-14, and you will have 5 grams of carbon-14 and 5 grams of nitrogen-14. After an additional 5,740 years, for a total of 11,480 years, you will have 2.5 grams of carbon-14 and 7.5 grams of nitrogen-14.

Half-life time varies greatly with different atoms/isotopes from seconds to years. Below is a mathematical formula that scientists use to calculate the half-life of various atoms. The information used for the mathematical equation was the same as the problem above. We started with 10 milligrams of C-14 that had a half-life of 5,740 years. The calculation was to find how much C-14 would remain after 11,480 years, which is two half-lives of C-14 (5,740 + 5,740 = 11,480).

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Half-life of iodine-131 is 8 years. If you have 200 milligrams of iodine-131, how much iodine will remain after 32 years? • How many half-lives will there be in 32 years? (divide # years by the years in a half-life) 32/8 = 4 Therefore, over 32 years, there will be four half-lives.

What Do You Think? 1.

If you have 40 milligrams of uranium-232 that has a half-life of 70 years, how much of uranium-232 will remain in 140 years?

If you have 200 grams of technetium-99m that has a half-life of six hours, how much will remain after 24 hours?

Fission and Fusion So far, we have talked about nuclear reactions that involve nuclear decay. Other nuclear reactions involve the bombardment of a nucleus with other particles. Fission: Fission is a nuclear reaction that occurs when a large nucleus collides with a small particle. The large nucleus splits into two or more smaller nuclei, releasing a large amount of energy. (In fact, the term ﬁssion comes from a Latin word meaning “to split.”) An example of a ﬁssion reaction is shown in the illustration at right.

During nuclear ﬁssion, a large nucleus splits into smaller nuclei.

Nuclear power plants are powered by ﬁssion reactions. The typical fuel is uranium-235, which undergoes a ﬁssion reaction when it is bombarded with neutrons. Fusion: Fusion occurs when two small nuclei collide and combine to form one larger nucleus. The word “fusion” means “to combine.” An example of a fusion reaction is shown in the illustration at right. This example shows the fusion of a deuterium nucleus with a tritium and tritium are both isotopes of hydrogen. nucleus. Deuterium (As you see in the illustration, each isotope has one proton. However, deuterium has one neutron, and tritium has two neutrons.) Along with the change in nuclear makeup, large amounts of energy are released during Nuclear fusion involves fusion. In fact, the energy released by stars, including the Sun, comes two small nuclei fusing to from nuclear fusion inside the star’s core. form one larger nucleus.

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What Do You Think? Label the following fusion or fission. Explain why you choose that label.

Study the graph to the right. The y-axis is the number of subatomic particles in the nucleus. Describe how this graph’s arrows help describe the difference in fusion and fission.

Look Out Looking to the Future: Fusion as an Energy Source Right now, nuclear power plants have been engineered to run on fission reactions only. While nuclear fission produces a great deal of energy, the hazards associated with maintaining fission-based nuclear power plants have many people concerned. Fissionable fuel is highly radioactive. The waste products of the fission process are also highly radioactive. These materials must be contained and kept shielded from humans. Normally, this can be accomplished. However, natural or man-made disasters could compromise any containment of these materials. This makes running a nuclear power plant difficult and potentially hazardous.

involved in the National Spherical Torus Experiment That is why scientists are exploring the possibility of developing power at Princeton University are experimenting with ways to plants that can run on nuclear fusion reactions. Fusion reactions are harness Scientists nuclear associated with far fewer hazards than ﬁssion reactions. Switching fusion as a source of power. from ﬁssion to fusion would improve the safety of nuclear power (Photo courtesy of the U.S. generation. Department of Energy)

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Connecting With Your Child Have your child use his or her reasoning and calculating skills to answer the following problems: If you start with 300 grams of an unknown substance and after six hours you have 75 grams of the unknown substance, what is the half-life of this substance? You order 100 grams of a radioactive substance that has a half-life of 10 hours. When the substance is delivered to you, there is only 20 grams left. How long did it take for your order to be delivered? Questions to ask your child: 1. What is the difference in atoms involved in a chemical reaction and a nuclear reaction? 2. What does the term half-life refer to? 3. How do you think a nuclear power plant provides energy?

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PS4AB Fission, Fusion, and Radioactive Decay

Reading Science Name:

Date:

Group:

Fusion or Fission? 1

Nuclear reactions can generate a great amount of energy. However, not all nuclear reactions are the same. There are two very distinct types of nuclear reactions— fusion reactions and fission reactions. What are the differences and similarities between nuclear fission and nuclear fusion? As you have learned, all atoms are made of subatomic particles called protons, neutrons, and electrons. In the simplest terms, nuclear fission occurs when large, unstable atoms split into smaller atoms to achieve a more stable state. Nuclear fusion is the opposite of fission. Fusion occurs when smaller atoms bind together to form a larger, more stable atom. In both cases, the reaction occurs to bring the atom to a more stable state by a reduction of potential energy.

Nuclear fission reactions occur when the nucleus of an atom is split into fragments. When this occurs, smaller fragments are created. Most often, the result is two fragments of relatively equal mass. How is this energy created? You can compare the mass of the starting atom and the masses of the final products. You will find that the mass of the final products is less than the mass of the starting atom. Yes, in this type of nuclear reaction, mass is lost! This means that matter is lost. This loss of matter is known as the mass defect. Remember, the law of conservation of mass is for non-nuclear changes. Nuclear reactions are described by conservation of mass-energy. The small amount of lost mass is converted directly into large amounts of energy. The energy created from this reaction can be used to generate electricity in power plants or for the huge explosions of atomic bombs.

One type of atom used for fission reactions is an unstable isotope of uranium known as uranium-235. The stable isotope is uranium-238. In order for this reaction to occur, a neutron must collide with the uranium-235 nucleus, creating uranium-236. This collision creates enough energy to split the newly formed nucleus into smaller nuclei. A huge amount of energy is released in the process. As the nucleus splits and releases energy, more neutrons are produced. These may collide with another uranium-235 nucleus, causing it to undergo fission. This will create more energy and produce even more neutrons. The reaction will become something called a chain reaction if enough neutrons are produced during collisions to keep the going. The minimum amount of material that is needed for the reaction to keep going is called the critical mass. The trouble with fission reactions is that radiation and nuclear waste products are created in the process. This is a problem, as many nuclear power plants use fission to produce energy, producing much radioactive byproducts as a result.

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PS4AB Fission, Fusion, and Radioactive Decay

Reading Science 4

Conversely, in fusion reactions, the nuclei from atoms with low atomic weights combine to create heavier nuclei. This reaction does not require neutrons in order to occur. Two light nuclei must collide with a great deal of energy. Fusion reactions require extremely high heat. In fact, the heat required can exceed several million degrees Celsius (yes, several million!) To put these types of temperatures in perspective, the temperature at the surface of the Sun is around 5,600ºC. Meanwhile, the temperature near the core of the Sun is calculated to be around 15 million degrees Celsius. This should give you a hint of how hot a nuclear reaction is. In fact, the Sun is a product of an ongoing fusion reaction that has been occurring for billions of years.

Why is such high heat required for these reactions? Remember, the protons of atoms are all positively charged. In order to combine atoms, the repulsion of the positive protons of the combining atoms must first be overcome. Extremely high heat gives the nuclei the kinetic energy needed to overcome the repulsion, and as shown with the Sun, fusion reactions are also very exothermic. Therefore, fusion reactions have the capability of producing more energy than is required to initiate the reaction. This creates a self-sustaining reaction that holds great promise for energy production. A fusion reaction will sometimes begin with a fission reaction to get it started. In the right conditions, it can sustain itself once started. One of the benefits of fusion reactions is that there are no radioactive byproducts. On Earth, fusion reactions result in the element helium. Heavier elements like beryllium or carbon are produced by fusion in stars. Hydrogen bombs are produced by fusion reactions in which several isotopes of the element hydrogen are combined to produce helium.

How can you remember the difference between these two types of nuclear reactions? Think in terms of vocabulary that you may already know. A fissure is a crack or opening that can appear on the surface of Earth. It is a separation. A fission reaction will therefore “separate” an unstable atom into parts. A fusion reaction will “fuse” two atoms together.

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PS4AB Fission, Fusion, and Radioactive Decay

Reading Science 1.

There are two distinct types of nuclear reactions: fusion reactions and fission reactions. In which reaction is the nucleus of an atom split into two or more atoms? A.

Fusion reactions

Fission reactions

Both nuclear reactions

Neither nuclear reaction

In order for fission reactions to be successful, they must be self-perpetuating, meaning they must be able to keep themselves going. What do you call the minimum amount of material that is needed for the reaction to keep going? A.

Isotope

Mass defect

Critical mass

Neutron

Our Sun is a star that is fueled by a specific type of nuclear reaction. Which type of nuclear reaction is this? A.

Fusion

Solar

Fission

Radioactive

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PS4AB Fission, Fusion, and Radioactive Decay

Reading Science 4.

Why is the fusion reaction not currently used to produce energy, especially as it is a “clean” form of energy that does not create radioactive or nuclear byproducts? A.

There are currently not enough fuels for fusion reactions.

Fusion reactions are highly endothermic, making them dangerous.

Fusion reactions do not yet produce enough energy.

The heat it takes to start a fusion reaction is too high to contain.

Fission reactions are currently used to provide energy for many different sources. Where does the energy produced during the reaction come from? A.

From the mass lost during the reaction, or the mass defect

From the mass created during the reaction, or the mass increase

From the critical mass of the reaction

From the protons created during the reaction

Why is the fusion reaction not currently used to produce energy, especially as it is a “clean” form of energy that does not create radioactive or nuclear byproducts? A.

There are currently not enough fuels for fusion reactions.

Fusion reactions are highly endothermic, making them dangerous.

Fusion reactions do not yet produce enough energy.

The heat it takes to start a fusion reaction is too high to contain.

Fission reactions are currently used to provide energy for many different sources. Where does the energy produced during the reaction come from? A.

From the mass lost during the reaction, or the mass defect

From the mass created during the reaction, or the mass increase

From the critical mass of the reaction

From the protons created during the reaction

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PS4AB Fission, Fusion, and Radioactive Decay

Math Connections Name:

Date:

Group:

Nuclear Chemistry Balancing Nuclear Equations

There are three main types of nuclear radiation characterized by the particles emitted by an element. Unstable atomic nuclei release particles during radioactive decay. Fill in the following table showing the symbol, charge number, mass number, penetration level, and an example of a material that can stop the particle. Symbol

Charge Number

Mass Number

Particle

Penetration Level (low, middle, high)

Stopped by

1. 2. 3. Use the following information to answer questions 4–18. Equations can be written to represent the reactants and products in a nuclear reaction causing alpha or beta emissions. In a balanced nuclear equation, the sums of the atomic masses and the atomic numbers, respectively, are equal on both sides of the equation. Balance the following reactions: 4. 5. 6. 7. 8.

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PS4AB Fission, Fusion, and Radioactive Decay

Math Connections 9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

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PS4AB Fission, Fusion, and Radioactive Decay

Writing Science Name:

Date:

LOOK

THINK When atoms produce alpha, beta, and gamma radiation, this is an attempt to regain stability. Due to an understanding of radioactive decay and nuclear action, scientists have been able to recreate the actions of nuclear fission and fusion in an effort to harness nuclear energy. Atoms in an unstable state are constantly striving to regain stability. In an effort to do so, atoms can emit various types of radiation such as alpha, beta, and gamma. During this radioactive decay process, atoms can produce new particles as well as transform into a different element entirely. Through the study of radioactive decay and radioactive emissions, scientists have been able to artificially induce this process for the benefit of energy harnessing as well as for destructive means of defense. These processes include fission, which is the splitting of an atom with a large unstable nucleus into smaller more stable particles, and fusion, which is the joining of smaller unstable particles into a larger more stable nucleus. Each process will release a great deal of energy that can be harnessed for use; however, fission reactions produce large amounts of radioactive material and fusion reactions require an extremely large amount of energy to produce the reaction. Historically, fission reactions have been used in nuclear power plants to produce energy as well as to produce the hydrogen bomb. Fusion reactions which prove to be much less efficient have not been used for energy production but have been used to produce the atomic bomb which was used by the United States during World War II. WRITE Using balanced nuclear equations, compare the mechanics of nuclear fission and fusion. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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PS4AB Fission, Fusion, and Radioactive Decay

Writing Science Topic:

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Physical Science

PS4C

Nuclear Energy as an Alternative Energy Source

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PS4C Nuclear Energy as an Alternative Energy Source

Student Journal Name:

Date:

Group:

Alternatively Speaking PBL Entry Document The U.S. Fish and Wildlife Services (FWS) has asked your school to help prepare a presentation for the U.S. Congress. The FWS believes that the presentation would be more persuasive if it were presented by the youth of the nation. The FWS would like the presentation to focus on how reducing our country’s use of foreign oil and incorporating more alternative energy sources can help conserve and protect local fish and plant life and help communities manage their local use. Your team’s task is to create a presentation that is informative and based on actual data. It should describe the pros and cons of using nuclear energy as an alternative energy source. Your presentation must include at least three benefits and three drawbacks for the use of nuclear energy as it relates to the generation of electricity at nuclear power plants. As you discuss the positives and negatives, you should explain why they impact society and Earth. The benefits and drawbacks must cover both global and local impacts. Special consideration will be given to the team that incorporates other applications of nuclear energy other than nuclear power plants. Your team will have a limited time to research, develop a plan, and create a presentation. You will present your idea to an audience in a 3-minute presentation. Divide your team into the following roles to complete the project: team leader, nuclear scientist I, nuclear scientist II, and presentation designer. Thank you for helping us take a step to create a cleaner and healthier place for our wildlife.

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Student Journal Alternatively Speaking PBL Expert Roles Team Leader As the team leader, you are responsible for ensuring that your team successfully completes the task on time. You will lead and keep track of all planning, encourage communication among your team’s experts, and make sure every team member fully understands all parts of the plan. Team members will present your final design in a 3-minute presentation. Nuclear Scientist I As the nuclear scientist I, you are responsible for exploring and researching the advantages to using nuclear energy as an alternative energy source. You will need to work cooperatively with your team to research the necessary information and to brainstorm the presentation design. Nuclear Scientist II As the nuclear scientist II, you are responsible for exploring and researching the disadvantages to using nuclear energy as an alternative energy source. You will need to work cooperatively with your team to research the necessary information and to brainstorm the presentation design. Presentation Designer As the presentation designer, you are responsible for creating the presentation. You can use brochures, PowerPoint slides, etc. You will also need to decide what each team member will do to contribute to the presentation and how you will handle the classroom discussion.

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STEMscopedia: NUCLEAR ENERGY AS AN ALTERNATIVE ENERGY SOURCE PS4C

Reflect Have you ever been to the nuclear power plants in Waynesboro or Baxley? Have you ever wondered where nuclear power came from and why people tell you that it can be dangerous? Does it really save the environment? Are there benefits and/or risks to nuclear power? atomic bomb: a bomb that is created and releases a vast amount of nuclear energy due to the process of fission of a radioactive element

fission: splitting of atoms.

Short History of Nuclear Energy All of these are great thoughts to help you better understand the evolution of nuclear energy. Uranium, which is an element found in Earth, was discovered in 1789. In 1895, x-rays were created by running an electric current through a vacuumed glass tube. In 1896, Henri Becquerel was working with compounds that contained uranium. By accident, he partially exposed some photographic plates that were covered in a box near where he was working. The plates are normally exposed when light shines on them. By 1898, radiation was discovered to kill bacteria in food. Ernest Rutherford named alpha and beta rays in 1899 and gamma rays in 1903. Researching and experimenting continued for the next three decades. In 1939, it was discovered that fission in other uranium nuclei could cause a high-energy chain reaction. Scientists continued to work to find out just how powerful Uranium-235 could be. More experiments were conducted, and in 1945, the first nuclear weapons test was held in New Mexico. Later that same year, atomic bombs were dropped on two Japanese cities. Less than two weeks later, Japan surrendered to end World War II. Nuclear energy has moved forward over the last 30 years. The first nuclear power plant was placed into service in 1974, and the Nuclear Regulatory Commission (NRC) was established. Nuclear power replaced hydropower as the second largest source of electricity in 1984. Nuclear power plants were being built all over the United States. While nuclear power has many benefits, it also comes with many risks. Discuss with your study buddy the benefits and risks of nuclear energy.

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STEMscopedia: NUCLEAR ENERGY AS AN ALTERNATIVE ENERGY SOURCE

How Nuclear Power Plants Produce Energy Nuclear power plants use the energy from radioactive materials such as Uranium-235 to heat water to steam. Pressure from the steam spins a turbine connected to a generator, producing electricity. In fact, this process is quite similar to how electricity is produced at fossil fuel-burning power plants. The primary difference is the source of energy for heating the water: fossil fuels (such as coal) versus radioactive fuel rods. This difference accounts for many of the advantages and disadvantages of nuclear power. Today, nuclear power is still considered the most environmentally safe energy source. But the future of nuclear energy will need to be renovated before it can be successful. We already know there are no greenhouse emissions from nuclear power, but the cost of renovating the already established power plants is extremely high. There are new federal safety guidelines that must be met, and the established plants range in age from 30 to 50 years old. To meet federal compliance, large amounts of money will be needed. The newest idea in the industry is called small modular reactors (SMRs), which are supported by the industry and government. These modular reactors are one-tenth the size of the current reactors. It would take many years and a tremendous amount of money to get a reactor the size of the current ones designed, obtained, and licensed through the NRC. With government support, the SMRs are likely the answer to the future of nuclear energy.

What Do You Think? Benefits and Risks Radioactive materials create serious health hazards, such as Chernobyl and, more recently, Fukushima in Japan. In both cases, large areas of the surrounding countryside have had to be depopulated and abandoned. Another disadvantage is the highly radioactive waste, which must be stored securely for thousands of years. The advantages of nuclear power are perhaps less widely known. The energy density of nuclear fuel is roughly one million times greater than that of fossil fuels. In fact, you would need to burn approximately 2,333 kilograms of coal to release the energy contained in one gram of uranium-235! Perhaps the greatest advantage is that the process of generating electricity from nuclear reactions produces no greenhouse gases. One other advantage is the low operating cost of the reactors. Once the building is done, operating the reactor is low. The average life of a reactor ranges from 40 to 60 years.

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STEMscopedia: NUCLEAR ENERGY AS AN ALTERNATIVE ENERGY SOURCE

Misconceptions Myth: Nuclear power plants can explode like a bomb. Truth: The power plant cannot explode because the uranium upgrading is too low. Myth: People get most of their radiation from nuclear power plants. Truth: Radiation occurs naturally in the atmosphere not from the power plants. Eating one banana could give you more radiation than a nuclear power plant. Myth: Nuclear energy is harmful to the environment. Truth: No greenhouse gas is emitted into the environment.

Try Now

Answer the following questions. 1.

Gamma, beta, and _________________________ are the three types of nuclear radiation.

Splitting of an atom is called ___________________________.

What do the letters NRC mean?

Name the element used in nuclear energy that was discovered in 1789.

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STEMscopedia: NUCLEAR ENERGY AS AN ALTERNATIVE ENERGY SOURCE

Connecting With Your Child Observing Nuclear Applications at Home Although you cannot conduct a home experiment involving nuclear radiation, there are several ways you and your child can observe applications of nuclear and atomic physics in your everyday lives. For example, some smoke detectors contain a radioactive isotope, Americium-241. Americium-241 emits alpha radiation, which ionizes air particles, causing the flow of an electric current. These ionized air particles attach to smoke particles, which hinders the flow of electricity and sets off the alarm. Look inside your smoke detector with an adult. Look but DON’T TOUCH the label that reads “Radioactive Americium-241.” This what causes the smoke detector to function properly. (Be sure to change the batteries in the detector.) If you live near a nuclear power plant, take a tour. Most plants have specific days and times that you can go and watch a video and see some of the power plant. If you do not live near one, watch a YouTube video on nuclear power plants. If your child’s school takes a field trip to a nuclear power plant, go as a chaperone. Discuss the importance of all types of fuels, especially the benefits and risks of nuclear power.

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PS4C Nuclear Energy as an Alternative Energy Source

Reading Science Name:

Date:

Group:

Nuclear Medicine 1

No parent wants to hear, “Your child has a brain tumor.” However, while a fast-growing tumor is frequently difficult to treat and long-term survival is limited, another type of brain tumor has a much more optimistic prognosis. With the use of localized radiation therapy, the prognosis appears to be even better.

Slow-growing tumors with few characteristics of cancer are labeled low grade. Gliomas are a type of tumor in the brain. Gliomas originate in the glia, the supporting cells within the brain. So a low-grade glioma is a slow-growing tumor that starts inside the brain. There are several problems with any tumor inside the brain. For one, there is limited space inside the skull. As a tumor grows, it compresses the brain inside the skull. Brain compression can lead to headaches, lethargy, seizures, and even death. Symptoms depend on which part of the brain is compressed and how much it is compressed. Another problem with brain tumors is that they are difficult to treat. Surgery is almost always the first choice for treatment. However, some areas of the brain are too deep inside the head or too important to cut during surgery. Chemotherapy can also be used, but it has many side effects and may have difficulty getting into the brain. Radiation therapy delivered from the outside is effective but commonly leads to serious long-term consequences. Young children are especially likely to lose brain function. Implantable radiation has significant advantages over these other treatments for certain brain tumors.

Breast and prostate cancer in adults has been successfully treated with implanted seeds of radioactive iodine (125I). A study published in 2011 reported on the use of implantable radiation for the treatment of low-grade gliomas in children. The picture above provides a sense of scale for the seeds. Each seed contains a small amount of radioactive iodine surrounded by a metal cover. The amount of radiation emitted by each seed is carefully measured and controlled during manufacturing. Seeds may be implanted either temporarily or permanently. Often a catheter, a thin flexible tube, is used to get the seeds into the tumor and hold them in the right place. The catheter is thin and does little damage to the brain.

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PS4C Nuclear Energy as an Alternative Energy Source

Reading Science 4

I has characteristics particularly suited to radiation therapy. It has a relatively long half-life of 59 days. Its decay releases low energy that only damages cells in close proximity to the radioactive source. Radiation can cause damage to DNA, the genetic material inside cells. When DNA is damaged, cells often stop dividing and die. Since cancer cells divide out of control, this effect can slow the growth of a tumor, or even kill it completely. But radiation does not discriminate between healthy and tumor tissue. Therefore, limiting the amount of radiation delivered to healthy tissue during treatment is the goal. Implantable radiation seeds are small and expose very little tissue to radiation. They are small enough to be inserted directly into tissue but powerful enough to kill tumor cells. Yet, they leave most healthy tissue unaffected.

Low-grade gliomas in children are treated by a combination of approaches. Surgery is performed if possible, removing the tumor either completely or partially. If the tumor cannot be removed completely or partially, radioactive seeds may be implanted to destroy tumor cells. If the tumor recurs, chemotherapy and/or traditional radiation may be attempted. While a diagnosis of a brain tumor is difficult to receive, new treatments increase the survival and quality of life of patients and their families.

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PS4C Nuclear Energy as an Alternative Energy Source

Reading Science 1.

In which part of the body do gliomas start? A.

Lungs

Heart

Brain

Skull

The first choice of treatment for brain tumors is usually __________. A.

surgery

chemotherapy

radiation therapy

alternative therapy

The implantable seeds are __________. A.

small cylinders

very large

covered in plastic

covered with protein

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PS4C Nuclear Energy as an Alternative Energy Source

Reading Science 4.

Which of the statements below is true for radiation released from 125I? A.

It has a great amount of energy.

It has a relatively long half-life.

It cannot penetrate metal.

It is difficult to measure.

The radiation released from 125I damages __________. A.

only the DNA of tumor cells

the cell membrane of both healthy and tumor cells

the DNA of cells very far away from it

the DNA of any cell close enough to it

Radiation therapy using implantable seeds __________. A.

is a promising treatment for brain tumors that cannot be removed by surgery

is most likely to cause a great amount of damage to healthy brain tissue

is only useful for tumors of the breast and prostate in adult patients

will replace all other treatments in the near future

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PS4C Nuclear Energy as an Alternative Energy Source

Math Connections Name:

Date:

Group:

Nuclear Applications Part I: Radioactive Decay Processes (Nuclear Chemistry) Many nuclides (the nuclei of specific isotopes) are radioactive, meaning they spontaneously emit radiation. Complete the table below to summarize the radioactive decay processes of nuclides. Process

Symbol

Change in Atomic #

Change in Mass #

Change in Neutron #

Alpha emission Beta emission Gamma emission Positron emission Electron capture

Part II: Medical Applications of Radioisotopes Radioisotopes are radioactive isotopes that have many applications in medicine. The radioisotopes used in medical applications have a fairly short half-life (t½) and decay rapidly without long-term health hazards. Radioactive decay is a first-order process whose rate is proportional to the number of radioactive nuclei, A, in a sample times the first-order rate constant, k, called the decay constant. This is

represented by the integrated rate law: where, Ao = the number of radioactive nuclei originally present in a sample A = the number of radioactive nuclei remaining at time t t = time When t = t½, the decay constant is equal to: Using the equations above to calculate the following: 1.

The decay constant for sodium-24, a radioisotope used medically in blood studies, is 4.63 × 10-2 h-1. What is the t½ of 24Na?

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PS4C Nuclear Energy as an Alternative Energy Source

Math Connections 2.

The t½ of radon-222, a radioactive gas of concern as a health hazard in some homes, is 3.823 days. What is the decay constant of 222Rn?

Phosphorus-32, a radioisotope used in leukemia therapy, has a t½ of 14.26 days. What percent of a sample remains after 35.0 days?

A sample of 41Ar, a radioisotope used to measure the flow of gases from smokestacks, decays initially at a rate of 34,500 disintegrations/min, but the decay rate falls to 21,500 disintegrations/min after 75.0 min. What is the t½ of 41Ar?

The decay constant for mercury-197, a radioisotope used medically in kidney scans, is 1.08 × 10-2 h-1. What is the t½ of mercury-197?

The t½ of carbon-14 is 5,730 years. What is its decay constant?

What percentage of 14/6 C (t½ = 5730 years) remains in a sample estimated to be 16,230 years old?

What is the t½ of iron-59, a radioisotope used medically in the diagnosis of anemia, if a sample with an initial decay rate of 16,800 disintegrations/min decays at a rate of 10,860 disintegrations/min after 28.0 days?

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PS4C Nuclear Energy as an Alternative Energy Source

Writing Science Name:

Date:

LOOK

THINK Nuclear energy was first utilized as a means to create bombs during World War II. Later, scientists started utilizing it to produce power. There have been many advances made in the nuclear industry; however, energy sources such as coal, gas, and hydro continue to produce more power than nuclear energy. Think about nuclear energy as an energy source. WRITE Argue the benefits, applications, and problems surrounding the use of nuclear energy as an energy source.

Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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PS4C Nuclear Energy as an Alternative Energy Source

Writing Science Topic:

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Physical Science

PS5A and PS7D

Particles and Energy in Matter

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PS5A7D Particles and Energy in Matter

Student Handout Name:

Date:

Changing States Activity 1. Divide into molecules as directed by your teacher. 2.

Each water molecule consists of three people: two hydrogen atoms and one oxygen atom. Link arms, with the oxygen atom in the middle.

All the molecules of water should group close together. Try to create an ordered structure with your elbows touching, but do not unlink your arms from your water molecule!

Shake in place. What state of matter are you?

As your teacher generates a heat flow, the molecules should slowly move away from one another (don’t unlink!), but stay contained in the same area.

What state are you now? What changed?

As your teacher continues the heat flow, the molecules should move quicker and spread out more.

What state are you now? What changed?

Your teacher will continue the heat flow, but you need to pretend that it is a tremendous amount of heat transfer. You will now break free from being a molecule and all be independent ions. Continue moving at a fast pace.

10. What state are you now? What changed?

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Student Handout 11. Your teacher will now stop the flow of heat. Re-form your original water molecules and start slowing down. 12. What state are you now? What changed?

13. Slowly return to your starting point, continuing to slow down. 14. What state are you now? What changed?

15. Create your original ordered structure, elbows touching, shaking in place. 16. What state are you now? What changed?

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PS5A7D Particles and Energy in Matter

Student Journal Name:

Date:

Group:

Part I: States of Matter Model I Describe the movement of the atoms in relation to each other. ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________

Model II Describe the movement of the atoms in relation to each other. ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________

Model III Describe the movement of the atoms in relation to each other. ________________________________ ________________________________ ________________________________ ________________________________ ________________________________ ________________________________

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PS5A7D Particles and Energy in Matter

Student Journal Part I: States of Matter, continued 1.

What phase of matter did each model represent?

Model I: _______________________________________________ Model II: _______________________________________________ Model III: ______________________________________________ 2.

How did the movement of the atoms change from model to model?

_______________________________________________________________________________ _______________________________________________________________________________ 3.

What did the shaking represent?

_______________________________________________________________________________ _______________________________________________________________________________ 4.

Describe heat’s effect on atoms.

How does the amount of contact atoms have with each other change as the state changes?

What are the limitations of this model that does not allow us to model plasma?

Explain how we could model plasma, including the materials that could be used and what they would represent.

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PS5A7D Particles and Energy in Matter

Student Journal Part II: Phase Change Diagram 1.

Record the temperature every 30 seconds in the table below. Time (min:sec)

Temperature (°C)

Time (min:sec)

7:30

:30

8:00

1:00

8:30

1:30

9:00

2:00

9:30

2:30

10:00

3:00

10:30

3:30

11:00

4:00

11:30

4:30

12:00

5:00

12:30

5:30

13:00

6:00

13:30

6:30

14:00

7:00

14:30

Temperature (°C)

Once you complete the line graph, attach it to this page.

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PS5A7D Particles and Energy in Matter

Student Journal Part II: Phase Change Diagram, continued 3.

Explain any patterns you see in your diagram.

Analyze your graph to determine the boiling point of your liquid.

_______________________________________________________________________________ 6.

How long did it take for the solid ice to melt completely?

_______________________________________________________________________________ 7.

Prove the direction of heat flow during the course of your activity.

Reflections and Conclusions 1.

Explain how the flow of thermal energy affects the particles of a substance as it changes from a gas to a solid.

Explain how the flow of thermal energy affects the particles of a substance as it changes from a liquid to a plasma.

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STEMscopedia: PARTICLES AND ENERGY IN MATTER

Reflect

PS5A and PS7D

Image you are eating an ice cream cone on a hot summer day with some friends. You are asked to join a game of tag, and leave your ice cream on the table in the hot sunlight. After several rounds of tag, you are hot and really want a bite of your frozen ice cream. When you look at your ice cream cone, you are surprised to see that the once solid ice cream has melted and is now a liquid. What happened to your ice cream cone? What do the particles inside the ice cream look like? Particles and Matter The ice cream melted due to the heat of the Sun. The heat of the Sun was absorbed, making the particles of the solid move faster, thus turning the solid into a liquid. All matter is made up of particles. These particles are always in constant motion and move at various speeds within the matter. The speed at which the particles move determine which state the substance will form. Gases and plasma have particles This illustration depicts how that move at very fast rates, while liquids and solids have particles that the substances change move at a much slower rate. between phases with the addition and removal of The four states of matter include: solids, liquids, gases, and plasma. heat. Each of the four states of matter is different. Certain properties, including temperature, density, and mass, determine which state the substance will become. The particles within a substance are microscopic and can’t be seen with the naked eye. When heat is added to the substance, the kinetic energy is increased and a phase change will occur. These changes can result in exothermic or endothermic reactions. When an exothermic reaction takes place, heat is released due to the excess energy from the system like during freezing. When heat is required for the reaction to take place, the reaction is said to be endothermic. An example of an endothermic reaction is melting.

What Do You Think? This image shows how the particles of solids are tightly packed together, Four States of Matter which only allows for minimal movement between the particles. Solids A solid is a form of matter that has its own definite shape and volume. Wood, paper, and gold are some examples of solids. The particles in a solid are packed tightly together and vibrate back and forward, allowing for more order within the solid. Due to the fixed shape and volume of solids, particles are close together and movement is limited. Solids are held together by forces called bonds. These bonds include ionic and strong covalent bonds. With the addition of heat, the particle of a solid will vibrate more aggressively but still remain close. If the vibration becomes too strong, the bonds will break and a phase change will occur. Solids also have the lowest kinetic energy out of the four states of matter, but they are the most dense. Solids are also incompressible due to the rigid shape of the particles.

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STEMscopedia: PARTICLES AND ENERGY IN MATTER

Liquid A liquid is a form of matter that has constant volume but no fixed shape. Instead, liquids flow freely and take the shape of its containers. Water, blood, and milk are examples of common liquids. The particles in a liquid are not as rigidly packed together as solids and move over each other easily. This allows the liquid to take the shape of its container. Due to the faster particle movement, liquid particles occupy more space and are less dense than solids. Think of the particles of a liquid as looking like jelly beans in a glass jar. They are close to each other, but there are spaces left for movement between the particles. The bonds of liquids are strong enough to keep the particles together but weak enough to This image shows the allow them to move around each other. Liquids can be described by particles of a liquid. Notice their viscosity or ability to flow. Viscosity is determined by three factors: the spaces between the size and shape of the particles, temperature, and intermolecular forces particles, which allow them in the liquid. Honey is a fluid that has a high viscosity, while water has to move over each other. a low viscosity. By increasing the temperature of the honey, you will increase the average kinetic energy and decrease the viscosity of the honey. This will allow the honey to flow faster. Liquids are also unique and form surface tension, which is the inward pull of the molecule at the surface of the liquid. This allows for water bugs to walk on the surface of the water. Particles of liquids have more kinetic energy than solids but less than gases. Liquids, like solids, are almost always incompressible. Gas A gas is a form of matter that not only flows to conform to the shape of its container but also fills the entire volume of its container. Gases have no definite shape or volume allowing the particles to move around freely This image shows the in all directions. Gases have more kinetic energy than solids and liquids, particles of a gas. These allowing for faster movement between the particles. Gases are easily particles have the most compressed due to the vast spaces between particles. This property space between each other also gives gas the most energy when compressed. There are no bonds and move freely within their between the particles in gases, which allows them to move about freely. container. Plasma Plasma is a hot ionized gas consisting of approximately equal numbers of positively charged ions and negatively charged electrons. Plasma has the most kinetic energy, and particles move about freely. It is also the most common phase of matter found in the universe. Examples are lightning bolts and stars.

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STEMscopedia: PARTICLES AND ENERGY IN MATTER

What Do You Think? Flow of Energy Many substances can exist in the four states of matter. Two factors that determine which state a substance will be are temperature and pressure. With the addition and removal of energy, a system can change from one phase to another. Look at the diagram below. In this diagram, we will use water as the example since most people are familiar with the physical phase changes that water undergoes. This diagram shows the six possible transitions that Melting matter can move between When solid ice melts, heat flows from the colder solid ice to the warmer surface that the ice is placed on. Heat is the transfer of energy from an object of higher temperature to an object of lower temperature. When solid ice melts, the particles of ice use the energy transferred to agitate the hydrogen bonds, keeping the solid ice together. This process makes the hydrogen bonds break and causes the ice to enter the liquid phase. The particles of the ice move more freely and faster, becoming a liquid. This is an endothermic process due to the requirement of energy to start the phase change. Vaporization After the water has turned into a liquid, heat is added to the system and causes the liquid to turn into gas or vapor. The particles in this phase will move faster than the liquid phase. This phase change requires energy and is endothermic. Sublimation Sublimation is the process by which a solid turns into a gas without becoming a liquid first. An example of this process is solid carbon dioxide or dry ice. This is a phase change that requires energy. The particles of solids gain energy by breaking their hydrogen bonds. This allows the particles to move faster to form a gas or vapor. This phase change is endothermic. Freezing When liquid water is placed into an environment with a low enough and sustained temperature (freezing point), the liquid water will turn into solid ice. This process happens because heat is removed from the water and the speed of the particles decreases. This also allows for a hydrogen bond to form between the molecules, giving the substance a more uniform look. This phase change is exothermic. Condensation Condensation takes place when water vapor molecules lose energy and particle speed decreases. When particle speed slows down, hydrogen bonds begin to form and allow the vapor to turn into a liquid. Condensation always involves the transfer of thermal energy. Condensation is an exothermic process.

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STEMscopedia: PARTICLES AND ENERGY IN MATTER

Deposition When a gas or vapor turns into a solid without becoming a liquid first, it is called deposition. An example of deposition is frost. The particles of the gas or vapor release energy and move slower. This process forms hydrogen bonds and allows the particles to have a rigid shape of a solid. This phase change is exothermic and does not require energy.

Look Out Watch out when using the words vapor and gas. They are similar but do not mean the same thing and should not be used interchangeably. Substances that are gases at room temperature are said to be gases. While a substance that is a solid or liquid at room temperature is referred to as a vapor when it changes to a gaseous state. Steam would be referred to as a vapor when it changes states from a liquid to a gas because water is a liquid at room temperature. When you see a solid or can’t see a gas, realize that the particles are always in constant motion. The motion may not be as fast as other phases, but there will always be motion. This is referred to as kinetic theory. The space and motion of the particle will determine the state or form of matter. When heat is added to any state of matter, typically the particles will increase the distance between each other. This means that most substances will expand when heated. Many students believe that solids do not expand, but they do. An example of this would be a wooden bridge expanding in the summer heat and shrinking in the winter with the lack of heat. What Do You Know? Apply what you know about particle movement, energy, and phase changes. Look at the heating curve below and identify what process is taking place at each point. 1. In which section of the curve would this substance have a defined volume and shape?

2. What is happening to the particles in the substance from point B to point C? What phase change is taking place, and is it exothermic or endothermic?

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STEMscopedia: PARTICLES AND ENERGY IN MATTER

3. In which section of the curve would this substance have a defined volume but no defined shape?

4. What phase change is happening from point D to point E? Is it exothermic or endothermic?

5. Draw below what the particles would look like between points A and B, points C and D, and points E and F.

Apply what you know about phase changes, particle movement, and energy to complete the following word match. Read the description and then place the correct letter in the blank. A.Gas

B. Solid

C. Liquid

D. Plasma

1. _______ Particle motion is most restricted. 2. _______ Most kinetic energy. 3. _______ The most common phase of matter in the universe found in all stars. 4. _______ Has a defined shape and volume. 5. _______ Has a defined volume but not a defined shape. 6. _______ Particles are easily compressed. 7. _______ Milk is an example of this state of matter. 8. _______ Wood is an example of this state of matter. 9. _______ Carbon dioxide is an example of this state of matter. 10. _______ Hot ionized gas.

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Connecting With Your Child Connecting With Your Child: Constructing a Heating Curve Using Water To help your child better understand phase changes and graphs, help your child construct a heating curve using water. You will need: • 10 ice cubes • Stove or hot plate (please do not let children use the stove alone) • A pot • Thermometer • Paper and pencil First, you will need to record the initial temperature of the ice. This will be point A on your heating curve. Then place the ice cubes into the pot and add heat. Record at what temperature the ice cubes melt; this will be point B. When the water turns into steam, this temperature will be point D. Use your data point to construct a heating curve for water and identify what phase changes and particle movements took place. Here are some questions to discuss with your child: 1. As heat is added to water, what happens to the particle movement within the water? 2. What are the four states of matter? Give an example of each. 3. What would a cooling curve look like? What type of phase changes would be on this type of graph?

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PS5A7D Particles and Energy in Matter

Reading Science Name:

Date:

Group:

Phases of Matter 1

When you consider phases of matter, do you recall the solid, liquid, and gas phases? Do you immediately think of the example of water since it is so prevalent here on Earth? Do you imagine it as ice, water, and vapor? Most people do. Ice is the solid form of water; water is the liquid form; and vapor is the gaseous form. Did you know there is also a fourth phase of matter called plasma? Let’s examine the particle arrangement and particle motion in all four phases.

Molecules in solids tend to be close together and arranged in a regular pattern. They are held in place by strong intermolecular forces. Because the molecules stay in place, solids do not flow; instead they retain their shapes. If you pick up a solid object and put it inside a different container, it would remain the identical shape. Therefore, solids have what is termed definite shape and definite volume. Examples of solids are plastic bottles, ice, sand, and aluminum foil. When solids are heated, their molecules move by vibrating in place. However, every solid has a melting point. Melting point is the temperature at which a solid changes to a liquid. As temperatures increase, intermolecular force weakens until, eventually, a solid melts and becomes a liquid. Strangely enough, even though heat energy is still being added to a solid, the temperature remains constant while the solid is melting. Why is this? Energy is being used to break the strong intermolecular forces holding the solid together. Once the object has melted, if heat energy continues to be applied, the temperature will begin to rise again.

Particles in liquids are not packed as closely together as particles in solids. Another difference is that they are not arranged in a regular pattern. Intermolecular forces are weaker, so molecules are not held tightly in place. In other words, liquids have no definite shape—they flow. On the other hand, like solids, liquids possess definite volume. So, if you pour a pitcher of water into a bowl, the water will take up the same amount of space; it will just flow to exist in the shape of the container. Examples of liquids are water, milk, blood, and honey. When liquids are heated, the molecules pick up speed and travel rapidly around the liquid. As more heat energy is added to the liquid, the intermolecular forces become weaker still. Eventually, molecules in the liquid transform into a gas. Every liquid has a unique boiling point, which is defined as the temperature at which matter changes from a liquid to a gas. Once again, as the phase change occurs (in this case from liquid to gas), energy is used to further break apart the intermolecular bonds, so the temperature remains constant.

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PS5A7D Particles and Energy in Matter

Reading Science 4

Particles in gas molecules are much farther apart than particles in solids or liquids. They are not arranged in any sort of pattern. The intermolecular force on molecules and atoms in gases is very weak. Just like liquids, gases will take the shape of their containers. Unlike liquids, they will flow throughout and fill the container. Gases have no definite shape and no definite volume. Examples of gases are air, water vapor, helium, oxygen, and carbon dioxide. When gases are heated, the particles speed up and spread out, increasing in temperature and volume.

What happens when gases are heated? Matter can be heated to almost unlimited temperatures. As matter approaches extremely high temperatures, a fourth phase of matter emerges: plasma. In gases, particles are neutral and possess no electrical charge. In plasma, particles are heated so much that they split and become charged. Electrons separate from atoms, creating positive ions and negative electrons. This changes the properties of matter. For example, plasmas can conduct electricity. Examples of plasmas are stars, lightning, and certain fluorescent lights and television sets.

Instead of three phases of matter, now you know there are at least four—solid, liquid, gas, and plasma. Some scientists consider glass a separate phase of matter too. Who knows how many phases of matter we may discover as technology and knowledge continue to advance!

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PS5A7D Particles and Energy in Matter

Reading Science 1.

Which phase of matter contains particles that split into ions and electrons? A.

Solid

Liquid

Gas

Plasma

Which phase of matter has definite shape and definite volume? A.

Solid

Liquid

Gas

Plasma

Why does temperature not increase even though heat energy is still being added? A.

Matter is as hot as it can get.

A phase change is taking place.

This situation is impossible—heating something always results in an increase in temperature.

The pressure is too high.

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Reading Science 4.

Why do you think the phases of solid, liquid, and gas were discovered first and are more well known than plasma? A.

Examples of solids, liquids, and gases are plentiful and easy to observe in the phases of water on Earth.

Plasma is dangerous.

Plasma is invisible.

Humans have no need for plasma.

Why do you think some scientists consider glass a different phase? A.

It is transparent.

It can melt.

It has properties that do not match with one specific phase of matter.

It is made of sand.

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PS5A7D Particles And Energy In Matter

Math Connections Name:

Date:

Group:

Particles and Energy in Matter Heating and cooling curves can be used to help visualize the phase changes when a substance is exposed to different temperatures. Use the heating and cooling curves below to help you understand the process of phase changes. The heating curve below shows the absorption of heat as 1 kg of water transfers from ice to steam.

What state is represented by Section A?_________________________________________

State changes are represented by Sections B and D. What is the phase change represented by Section B? ___________________ Section D? _____________________

What is the slope of the two lines? ____________ What does this particular slope tell you about the temperature during a phase change? ___________________________________

During which phase change is the most heat absorbed? ____________________________

Which state spans the longest temperature range? ________________________________

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PS5A7D Particles And Energy In Matter

Math Connections The heating curve below shows the changes in iron as it transitions from a solid to a gas. Use the graph to answer the questions below.

Based on the heating curve, what is the approximate melting point of iron? ______________

Based on the heating curve, what is the approximate boiling point of iron? _______________

Draw in the particle arrangement in the boxes above each section of the heating curve based on the phases they represent.

Does it take longer for iron to change from a solid to liquid or from a liquid to a gas? _____________________

10. Temperature is a measure of average kinetic energy. A change in temperature equals a change in kinetic energy. What sections show a change in kinetic energy? ______________ 11. Which section shows the largest change in kinetic energy? ___________________________

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PS5A7D Particles and Energy in Matter

Writing Science Name:

Date:

LOOK

THINK When conducting experiments related to changes in the state of matter, many scientists use graphs to show the heating or cooling curve of a material. Contrary to the term “curve” and to one’s thinking, the graph behaves differently than expected. Look at the graph below.

WRITE Analyze whether heating or cooling is taking place to explain the particle movement in relation to phase changes seen on the graph. Then, explain the dynamics of the graph, including the curves and plateaus as they relate to the conversion of water. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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PS5A7D Particles and Energy in Matter

Writing Science Topic:

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Physical Science

PS5B

Behavior of Gases

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PS5B Behavior of Gases

Student Handout Name:

Date:

Boyle’s Law: Increased Pressure Record your observations of the cartesian diver inside the bottle. State your reasons (conclusions) for this reaction. Observations Record your direct observations.

Conclusions Describe what was occurring inside the diver on the particulate level as pressure was increased. Specifically, state how pressure affected the volume of the gas inside the diver.

Boyle’s Law: Decreased Pressure Record your observations of the cartesian diver inside the bottle. State your reasons (conclusions) for this reaction. Observations Record your direct observations.

Conclusions Describe what was occurring inside the diver on the particulate level as pressure was increased. Specifically, state how pressure affected the volume of the gas inside the diver.

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PS5B Behavior of Gases

Student Journal Name:

Date:

Group:

Station One: Crush the Can 1.

Using arrows to represent pressure, draw the air inside of the can before, during, and after the activity. Before

When Boiling

Right After Cooling

What does the activity show about the relationship between temperature and pressure? What type of proportional relationship is it?

Station Two: The Spinner 1.

How does this activity show the relationship between temperature and density? What type of proportional relationship is it?

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Student Journal Station Three: Chill Out, Warm Up 1.

After 2 min, record the temperature of the ice water and the volume of air in the syringe.

Temperature: ______________ Volume: _________________ After 2 min, record the temperature of the warm water and the volume of air in the syringe.

Temperature: ______________ Volume: _________________ What does this activity show you about the relationship between temperature and volume? What type of proportional relationship is it?

Station Four: Steak Sauce Gas? 1.

What does the activity show about the relationship between temperature and pressure? What type of proportional relationship is it?

Station Five: Not So Squishy 1.

Draw the appearance of the marshmallow once you pulled back on the plunger and then after the plunger was released. Pulled Back

Released

What does the activity show about the relationship between volume and pressure?

_______________________________________________________________________________ _______________________________________________________________________________ 174

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STEMscopedia: BEHAVIOR OF GASES PS5B Reflect Have you ever been to an outdoor celebration or carnival where there were lots of balloons? You may have noticed that during the hot afternoon, the balloons looked so full of air that they might pop and that they seemed to strain at the strings attached to them as if they were trying to escape into the sky. Later in the evening, the Sun went down, the air cooled, and the balloons looked different. They seemed to have lost some of their air and yet gained weight because their strings were no longer pulled tightly upward. What caused these changes in the balloons? Let’s consider how the balloons are made. A balloon is a flexible container that can hold a gas. The gas inside a balloon is usually air or helium. Air is a mixture of nitrogen, oxygen, and other gases that are found in the atmosphere. Gases, like other forms of matter, are made up of atoms and molecules. When you fill a balloon with a gas or air, it inflates because of all the atoms and molecules you are pushing into it. The more particles you put in a balloon, the larger it becomes. The gas molecules in a When you inflate a balloon and tie a knot at the end, you are creating sealed balloon behave like a closed system. A closed system does not allow matter to move in or the gas molecules in this out of the system. The number of gas particles in this closed system will closed system. remain the same. The gas particles inside the balloon are in constant motion, bouncing off each other and the inside walls of the balloon. Changes in the conditions inside and outside the balloon can affect the motion of these particles without adding or taking away matter.

Look Out Does air have weight? Some people think it does not. How can you find out? Try this experiment: You will need two identical, uninflated balloons; two 30-centimeter pieces of string; and a clothes hanger. • Blow up one balloon and tie a knot at its end so no air escapes. • Tie a piece of string around the neck of each balloon, then tie the other ends of the strings to each side of the hanger. • Balance the hook of the hanger on your index finger and let the two balloons hang freely. What did you observe? The side of the hanger tied to the balloon with air hung lower than the side with the empty balloon. The inflated balloon seemed to be heavier. Since the only difference in the two balloons was that one had air, we can conclude that air has weight. © Accelerate Learning Inc. - All Rights Reserved

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STEMscopedia: BEHAVIOR OF GASES How Do Temperature, Pressure, Volume, and Density Affect Gases in a Closed System? Temperature is a measure of the average kinetic energy of atoms and molecules in an object. Kinetic energy is the energy that moving particles have. The faster the particles move, the higher the kinetic energy and the higher the temperature will rise. One way to increase the kinetic energy of the particles in a balloon is to add heat. Balloons absorb radiant energy in the form of heat from sunlight. The temperature of the air inside the balloon rises. Does increasing the temperature of the gas inside the balloon affect any of its other physical properties, such as pressure, volume, and density? Volume is the amount of space matter occupies. When the balloon is heated and the kinetic energy of the particles in the gas increase, they will move faster and bounce off each other and the walls of the container more often. This action will cause the gas particles to push away from each other and expand in all directions, increasing the volume of the balloon. Likewise, if you cool the gas inside the balloon by taking away heat, the particles will have less kinetic energy and slow down. They will move closer together, and the balloon will lose volume. Pressure is defined as force applied to a unit of area. In the case of the balloon, the pressure is caused by the gas particles inside the balloon colliding with the inside wall of the balloon. The material of the balloon forms the area over which the collisions occur. The more collisions of gas particles and a greater force of each collision with the outer walls of the balloon increase its pressure. If the pressure becomes too great for the strength of the material from which the balloon is made, it could rupture, or pop. How does pressure affect temperature and volume? Increased pressure from the gas particles pushing outward on the walls of the balloon will cause an increase in volume. If the particles have a greater force and cause more collisions, they are also moving faster. If the walls of the balloon do not expand to allow the particles to move farther apart, there will be more collisions between particles and a rise in the temperature of the gas inside the balloon will occur. Therefore, increasing the pressure of a gas in a closed system can also increase the temperature of the gas if the volume remains constant. You can say that temperature varies directly with pressure. In other words, if the pressure increases, so too will the temperature if there are no other changes in the system. Some fire extinguishers contain carbon dioxide gas that is compressed under a great amount of pressure. The container must be made of a material, such as metal, which is strong enough to hold the pressurized gas without expanding. When the carbon dioxide is sprayed out of the extinguisher, it expands rapidly and cools into a solid foam that can smother the fire. When the volume expands, the pressure and temperature decrease. This is called an inverse relationship, where one factor increases and causes another to decrease.

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STEMscopedia: BEHAVIOR OF GASES You may wonder where density fits into this scenario. Recall that density is mass per unit volume; the denser an object is, the more likely it is to sink in a fluid. Fluids are matter that flows. Liquids and gases are fluids. If you heat a balloon so that the gas inside expands, it will become less dense because the volume is increasing while the mass remains constant. If you cool the gas inside a balloon, it contracts and becomes denser. If the balloon is less dense than the surrounding fluid, it will rise. If the balloon is denser than the surrounding fluid, it will sink.

Try Now Predict what will happen to other properties of the gas in a balloon as the density, pressure, temperature, volume, and kinetic energy of particles in a balloon increase (+) or decrease (-). Density +

Pressure

Temperature

Volume

Kinetic Energy

Connecting With Your Child Try this experiment at home to compare how temperature changes affect a gas in a closed system. Materials needed: • 3 nine-inch balloons • Measuring tape • Handheld hair dryer

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STEMscopedia: BEHAVIOR OF GASES Procedure: Inflate the three balloons to equal sizes and tie the ends. Measure and record the circumference of each in centimeters. • Place one balloon in the freezer for 10 minutes. • Set the hair dryer on low heat and hold it near another balloon for 10 minutes. • Leave the third balloon at room temperature for 10 minutes. • At the end of 10 minutes, measure and record the circumference of each balloon again.

Cold Balloon

Room Temperature Balloon

Hot Balloon

Before

After

Discussion Discuss your observations and results of this activity with your parent. Discuss how each balloon is a closed system, and discuss how temperature changes affect the volume of each balloon. Infer how temperature changes affect the density of a gas in a closed system.

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PS5B Behavior of Gases

Reading Science Name:

Date:

Group:

How Measuring Pressure Threw Off the Football World 1

During a recent National Football League (NFL) game, one of the teams was accused of cheating by underinflating footballs by as much as 2 lbs. per square inch (psi), which is a fraction of 1 psi. Several prominent scientists offered their opinions, but in the end, it was the ideal gas law that saw center stage.

The ideal gas law, PV = nRT, shows what happens to an ideal gas when its pressure, volume, or temperature changes. If you change a variable on one side of the equation, the other side will have to adjust in order to keep the equation balanced. If temperature goes up, volume will go up as the gas expands, and vice versa. If the pressure goes up, temperature goes down, and vice versa. P = pressure V = volume n = moles R = a constant T = temperature

So what does that have to do with the underinflated footballs? The NFL found that 11 of the 12 footballs handled by one of the teams were underinflated. The accused team’s coach suggested that cold weather caused the change in pressure. After several scientists quoted the ideal gas law and the impossibility that outside or locker room conditions could have caused the change in pressure, the offending team didn’t seem to stand a chance for vindication.

However, an independent laboratory found that the scientists who spoke against the team did their math wrong and did not take into account absolute pressure. Ordinary pressure gauges use atmospheric pressure in excess of one atmosphere. When the scientists had plugged in the football air pressure into the ideal gas law, they did not add that pressure to the existing atmospheric pressure which would have revealed the absolute air pressure. “They forgot to convert the pressure into absolute pressure, so they were using gauge pressure, not absolute pressure,” said Thomas Healy, a graduate student at Carnegie Mellon and researcher at HeadSmart Labs.

When word got out, the scientists had to revise their calculations and issue a correction and an apology. When all the variables were studied, the HeadSmart Labs researcher added, “What our research brought in was you can’t only look at the temperature, you have to bring in the fact that it was raining. Our hypothesis was that when leather gets wet, it starts to expand some, which increases the volume and decreases the pressure.” That alone would account for the air pressure differences.

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PS5B Behavior of Gases

Reading Science 1.

What connection did the ideal gas law have with the football controversy? A.

Questionable volume measurements

Questionable temperature measurements

Questionable pressure measurements

Questionable mole measurements

Which of the following relationships does the equation for the ideal gas law show between the variables? A.

As pressure goes up, temperature also goes up.

As pressure goes up, temperature goes down.

As temperature goes up, pressure goes down.

As temperature goes down, pressure goes up.

The equation for the ideal gas law also shows which of the following relationships between the variables? A.

Pressure is directly proportional to volume.

Volume is indirectly proportional to pressure.

As pressure goes up, volume goes up.

Pressure is indirectly proportional to volume.

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PS5B Behavior of Gases

Reading Science 4.

What error did the scientists make originally with the ideal gas law and the underinflated footballs? A.

They did not find the absolute pressure, which combines the atmospheric pressure with the football gauge pressure.

They did not divide the absolute pressure by the gauge pressure.

They did not subtract the gauge pressure from the absolute pressure.

They used the wrong pressure gauge.

In their final analysis of the underinflated footballs, what environmental factor was omitted from the scientists’ considerations? A.

The temperature of the quarterback’s hands

The age of the gauge

The number of measurements taken

The rain making the football wet

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PS5B Behavior Of Gases

Math Connections Name:

Date:

Group:

Gases have various chemical and physical properties. Gases can be described in terms of their pressure, temperature, volume, and density. The relationships between these characteristics are used to predict their behavior in closed systems.

Volume (cubic meters [m³])

Pressure (mmHg)

5 4 3 2 1

7.5 9.375 12.5 18.75 37.5

Plot the data in the table using the graph on the right.

What is the shape of the graph?

Pressure (mmHg)

The table below shows the relationship between the volume of a gas in a container being pressed down by a changing pressure. The temperature and mass of the gas are held constant.

Is it proportional? 3.

Volume (m3)

What is the relationship between the volume and the pressure of the gas in the container?

Volume (cubic meters [m3])

Pressure (mmHg)

.20 .25 .33 .50 1

7.5 9.375 12.5 18.75 37.5

Plot the data in the table using the graph on the right.

What is the shape of the graph? Is it proportional?

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Pressure (mmHg)

The table below shows the relationship between the inverse of the volume versus the changing pressure in a closed system. The scenario is the same as above; however, the volume is displayed as its inverse (1/volume). This is called Boyle’s Law.

1/Volume (1/m3)

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PS5B Behavior Of Gases

Math Connections Volume (cubic meters [m3])

Pressure (mmHg)

0.25 0.50 0.75 1.00 1.25

120 240 360 480 600

Plot the data in the table using the graph on the right.

What is the shape of the graph?

Temperature (Kelvin)

The table below shows the relationship between the volume and temperature of a gas when the pressure of the force is held constant. This is called Charles’ Law.

Volume (L)

Is it proportional? 8.

What is the relationship between the temperature and the volume?

Volume (cubic meters [m3])

Pressure (mmHg)

0.25 0.50 0.75 1.00 1.25

93.25 186.5 279.75 373 466.25

Plot the data in the table using the graph on the right.

Temperature (Kelvin)

The table below shows the relationship between the pressure and temperature of a gas when the volume and amount of gas are held constant in a closed system. This is called Gay-Lussac’s Law.

10. What is the shape of the graph?

Pressure (atm)

Is it proportional? 11. What is the relationship between the temperature and the volume?

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PS5B Behavior of Gases

Writing Science Name:

Date:

LOOK

THINK Modernized hot air balloons work off of propane tanks in a process that is very similar to using a propane burner on a stove. The liquid propane is sent through the steel coils. Then, the pilot light is lit to warm the propane in the coils. This causes the propane to be changed from liquid propane to a gas and then ignited. The heat energy is used to change the temperature of the air inside the balloon. WRITE Imagine you have taken a job as a hot air balloon driver. Explain the relationship between temperature, pressure, volume, and density and the effect they have on the operation of a hot air balloon as it floats through the air.

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PS5B Behavior of Gases

Writing Science Topic:

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Physical Science

PS6ABC

Solutions

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PS6ABC Solutions

Student Handout Name:

Dissolution Rates

Date:

Sugar–Water Dissolution

Prediction: Which beaker will dissolve first? (Rank them.) Granulated sugar beaker: ____________ Powdered sugar beaker: ____________ Sugar in the Raw beaker: ____________ Results: Granulated Sugar

Powdered Sugar

Sugar in the Raw

Time to dissolve:

_______________

Dissolution Rank:

_______________

Describe the difference between the substances placed in each of the three beakers.

How did these differences affect the rate of dissolution of these substances?

Explain WHY you think surface area affects dissolution.

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PS6ABC Solutions

Student Journal Name:

Date:

Group:

Background 1.

Define aqueous solution and specify what it contains.

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 2. What is solubility, and how is it usually expressed for solutions? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 3. Explain how the dissolving process occurs in solutions until equilibrium is reached. Be as specific as possible. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 4. What factors affect the rate of dissolution? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 5. What factors affect the rate of crystallization? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 6. How do temperature and concentration relate to the saturation of a solution? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 7. Define the term ion and state how this relates to electrolytic solutions. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

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PS6ABC Solutions

Student Journal Part I: Plan your Investigation 1.

My question of inquiry:

_______________________________________________________________________________ _______________________________________________________________________________ 2. What do you need to do to answer this question? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 3. What are the variables that you will observe? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 4. What do you predict will occur? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 5. What materials, equipment, and technology will you need for this investigation? ________________________________________ _______________________________________ ________________________________________ _______________________________________ ________________________________________ _______________________________________ ________________________________________ _______________________________________ 6.

What safety precautions must be taken in this investigation?

Procedures: Record your procedure on the back of this worksheet or in your lab journal if needed.

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PS6ABC Solutions

Student Journal Part II: Implement Your Investigation Collect, Record, and Organize Data Compound

Data

_____°C (Initial)

25°C

40°C

60°C

80°C

Solubility (g) Conductivity Solubility (g) Conductivity Solubility (g) Conductivity Solubility (g) Conductivity Solubility (g) Conductivity Solubility (g) Conductivity

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PS6ABC Solutions

Student Journal Part II: Implement Your Investigation, continued Analyze Data 1.

Use this page to create your solubility graph from the data table. Highlight your assigned compound in red, and then graph the results from the rest of the class in various colors. Label each line with the corresponding compound and create a legend for your graph. Remember, the independent variable should be on the x-axis and the dependent variable on the y-axis.

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Student Journal

PS6ABC Solutions

Part II: Implement Your Investigation, continued Analyze Data 1.

Why did the different compounds have different solubilities? What factors may have affected this?

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 2. Describe the processes that occur in the electrolytic solutions that allow for the movement of an electric current. In other words, what is occurring at the particulate level? ________________________________________________________________________________________ ________________________________________________________________________________________ _______________________________________________________________________________ 3. How did the electrolytic and nonelectrolytic solutions differ as you heated them? Explain this behavior. ________________________________________________________________________________________ ________________________________________________________________________________________ _______________________________________________________________________________ 4. How did you determine whether your solution was an electrolyte or nonelectrolyte? ________________________________________________________________________________________ _______________________________________________________________________________ 5. Describe what occurred in the supersaturated solution demonstration. Why did the solution behave that way when the crystal was added? ________________________________________________________________________________________ _______________________________________________________________________________ 6. How did you know when your solutions became saturated? What occurred in the beaker? ________________________________________________________________________________________ _______________________________________________________________________________ 7. Explain why ions need to be present in solution for an electric current to occur and whether the ion concentration in solution affected conductivity. ________________________________________________________________________________________ _______________________________________________________________________________ 8. How did the solubility graph that you created relate to the temperature at which the various solutions become saturated? What does this tell you about the saturation levels of each compound? ________________________________________________________________________________________ _________________________________________________________________________________ _______________________________________________________________________________ © Accelerate Learning Inc. - All Rights Reserved

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PS6ABC Solutions

Student Journal Reflections and Conclusions 1.

Was your prediction correct or incorrect? Explain.

Was there a relationship between the variables you observed?

Where could errors have been made while collecting or organizing data?

What do you conclude about this investigation?

What would you do differently if you were to conduct this experiment again?

Using all of the following terms, develop a graphic organizer. Use additional paper if needed.

Terms: solute, solvent, solution, ionic compound, molecular compound, ions, positive charge, negative charge, neutral charge, conductivity, electrolyte, nonelectrolyte, agitation, dissolution rate, surface area, crystallization, solubility, temperature, saturated, unsaturated, supersaturated

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STEMscopedia: SOLUTIONS PS6ABC

Reflect Imagine you are making lemonade by stirring lemonade mix into a glass of water. One spoonful of mix would likely dissolve easily in the water, producing a solution. What would happen if you added another spoonful of mix to the solution? Depending on how much water is in the glass, the additional mix may take longer to dissolve. If you add another spoonful or two, you would reach the point where the lemonade mix no longer dissolves in the water. The lemonade mix that does not dissolve settles to the bottom of the glass. Why is there a limit to how much lemonade mix dissolves in water? A mixture is a substance created by mixing at least two materials together without causing a chemical reaction. There are two types of mixtures: heterogeneous and homogeneous. Heterogeneous mixtures are mixtures in which the parts are not distributed uniformly throughout the mixture. Examples of heterogeneous mixtures are concrete, a bowl or mixed nuts, a bag of Skittles (multiple colors), sand at the beach (various rocks), and trail mix. Homogeneous mixtures have uniform composition and are called solutions. In a solution, it is impossible to see where one component ends and another begins. Examples of solutions include salt water, sugar water, and rubbing alcohol. Water Water is one of the most abundant liquids on Earth. It is also one of the best solvents. A solvent is a substance in which another substance dissolves. Water dissolves many different types of substances. Solutions in which water is used as the solvent are known as aqueous solutions. Salt water, sweet tea, coffee, apple juice, and sugar water are examples of aqueous solutions. Concentration Concentration is a measure of the amount of a solute dissolved within an amount of a solvent. Concentration is a scientific and precise way of calculating how dilute or strong a solution is. Concentration is expressed as a ratio. It compares the amount of the solute to the total amount of the mixture. The ratios can be stated in a variety of ways. • One way is to use the units grams per liter (g/L). This is best used when a solid solute is dissolved in a liquid solvent. An example would be sugar in iced tea. The concentration might be 28 grams per liter. • Another way to express the concentration is as a percentage. It is calculated by expressing the number of parts of solute found in 100 parts of the solution. It is usually measured in grams. For example, sugar in coffee might be three parts sugar to every 100 parts of the coffee-sugar solution. Therefore, the concentration would be three percent. • The concentration of a solution can also be measured in parts per million (ppm). This method is usually reserved for very dilute solutions for which a percentage would not be specific enough. It often uses milligrams (mg) as the unit. For example, allergens such as mold, cedar, and grasses, are measured in ppm. Pollutants are also measured this way. • Molarity is another option for measuring concentration. To simplify, a mole is a unit that is used to explain the number of particles in a substance. To calculate molarity, the solute (in moles) is divided by the volume of the solution.

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STEMscopedia: SOLUTIONS Factors of Solubility Polarization Why is water such an effective solvent? An important reason is that water molecules are polar. A polar molecule is a molecule whose layout of the atoms has one end with a positive electrical charge and the other side with a negative charge. In other words, they have opposite, partial A water molecule is polar. charges. A water molecule (H2O) consists of two hydrogen atoms (H), The oxygen atom (red) has each of which shares its electron with a central oxygen atom (O). The shared electrons are attracted more to the oxygen atom, so it acquires a a partial negative charge, and each hydrogen atom partial negative charge. Meanwhile, the hydrogen atoms acquire partial (white) has a partial positive positive charges. charge. What does this have to do with solubility? Ions are particles with electric charges, and ionic compounds are compounds formed between negatively and positively charged ions. When other polar molecules or ionic compounds are mixed with water, their positively charged components are attracted to the oxygen atoms in water molecules and their negatively charged components are attracted to the hydrogen atoms in water molecules. The chemical bonds joining some compounds are strong enough to withstand the attractive forces from water molecules. Other compounds, however, are broken apart. This is what happens when a substance dissolves. In contrast, nonpolar substances such as vegetable oil do not dissolve in water. Instead, the denser substance sinks beneath the less dense substance.

Look Out Do not confuse molecules that are polar and compounds that are electrolytes. Polar molecules have partial charges—one end is partly positive, and the other end is partly negative—but they are not composed of ions, which have full positive or negative charges. Like electrolytes, polar molecules dissolve in water. Unlike electrolytes, however, polar molecules do not break apart into ions when they dissolve, and so they do not produce electrolytic solutions. For example, table sugar is a polar molecule that dissolves in water and is a nonelectrolyte. In contrast, table salt is an ionic compound that dissolves in water and is an electrolyte. What Do You Know? Identifying Electrolytes and Nonelectrolytes A common way to classify aqueous solutions is to determine whether they are able to conduct an electric current. An electrolytic solution conducts electricity. These solutions contain electrolytes, substances that separate into ions (particles that have net electric charges because they have gained or lost electrons) when dissolved in a solvent. The ions are electric charges, which can move within the solution and allow it to conduct electricity. A non-electrolytic solution does not contain electrolytes and so does not conduct electricity.

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STEMscopedia: SOLUTIONS Sodium chloride (NaCl), or table salt, is a strong electrolyte. When sodium chloride dissolves in water, the sodium ions (Na+) and chloride ions (Cl−) separate from each other. The ions disperse evenly throughout the water, which becomes an electrolytic solution. In contrast, substances such as ethanol (C2H5OH) and normal table sugar, or sucrose (C12H22O11), are non-electrolytes. A granule of sugar large enough for us to see consists of many individual sugar molecules joined together. When sucrose dissolves in water, the connections between the different sugar molecules are what break apart, not the sugar molecules themselves. The resulting solution contains evenly dispersed water and sugar molecules. Because ions are not produced, the solution does not conduct electricity. If an electrolytic solution is connected to the conductivity meter, electric current will flow to the bulb and produce light. If a non-electrolytic solution is connected to the meter, the light bulb will not turn on.

The diagram shows a conductivity meter. • Is the meter connected to an electrolytic or a non-electrolytic solution? How do you know? • Can you name some non-electrolytic solutions? • What are some electrolytic solutions? • What are some practical uses for electrolytic solutions? The following terms are associated with electrolytes or non-electrolytes. Write each term in the correct place on the Venn diagram on the next page. Place terms associated with both electrolytes and nonelectrolytes in the middle. Electrolyte/Non-electrolyte Terms: • Sodium chloride dissolved in water (salt water) • Will dissolve in water • Dissociates into ions • Lights a bulb when connected to a conductivity meter • Conductor of electricity • Does not dissociate (split into ions) in solution • Can be polar substances • Not an electrical conductor • Does not light a bulb when connected to a conductivity meter • Table sugar, or sucrose, dissolved in water

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STEMscopedia: SOLUTIONS

Temperature The temperature of a solution also affects the solubility of a solute. Typically, at higher temperatures, the solubility of solid and liquid solutes increases. You can dissolve more sugar in hot coffee than in iced coffee.

In contrast, at higher temperatures, gases are less soluble in liquids. If you were to leave a can of soda in a car on a very warm day, it might explode. The soda is a mixture of gas (carbon dioxide) and liquid (water). At warmer temperatures, the gas particles move more quickly, so it is easier for them to escape from the solution. As they collide with greater force against the walls of the can, pressure builds inside the can. Eventually, the pressure may cause the can to explode.

What Do You Think? The following graph shows the effect of temperature on a solute dissolving in a solvent. The x-axis shows the temperature of the solvent (in °C). The y-axis shows the mass of solute (in g) that dissolves at each temperature.

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STEMscopedia: SOLUTIONS • • • •

Analyze the graph and predict what the mass of the solute would be if the temperature were raised to 90 degrees Celsius. How do you know this? What can you conclude about the relationship between temperature and solubility for these substances? Do you think the solute could be a gas? Why or why not? What are a few of the solvent/solute combinations that would fit with this graph?

Pressure Changes in pressure do not drastically affect the solubility of solids and liquids. However, pressure changes can have an enormous effect on the solubility of gases in liquids. Gases are more soluble at high pressures than at low pressures. This is a serious concern for scuba divers. Air is a mixture of gases, primarily nitrogen and oxygen. As we breathe air, these gases are dissolved in our blood. Deep underwater, the pressure is much greater than at the surface, so a scuba diver’s blood contains more dissolved nitrogen and oxygen. The body cannot use the extra nitrogen, so as the diver begins to ascend, the extra gas is forced out of the blood, forming bubbles that go into the bloodstream as well as tissues and muscles. Divers who ascend too quickly may suffer from decompression sickness, or “the bends.” When experiencing the bends, a diver can feel pain or weakness throughout his or her body, and, in some cases, shortness of breath. Saturated vs. Unsaturated Solutions Recall the glass of lemonade at the beginning of this companion. Initially, a small amount of lemonade mix was added to the water. The resulting solution was unsaturated because additional solute (lemonade mix) could be dissolved in the solvent (water). More and more lemonade mix was added, until eventually no more mix would dissolve. At this point, the solution was saturated. Any mix added after this point settled to the bottom of the glass. It is possible to dissolve more solute in a saturated solution by increasing the solution’s temperature or the pressure acting on it. Such a solution becomes supersaturated. When a supersaturated solution is brought to normal pressure or temperature conditions, the additional solute precipitates from the solution. Precipitate means to cause a substance to come out of a solution and accumulate in solid form. Adding more solute or disturbing the solution—for example, by tapping on the container—can also trigger this precipitation. Many supersaturated solutions form crystals. Factors That Affect Solubility Rates The speed at which a solute dissolves in a solvent—or the rate of dissolution—depends on three factors: the temperature of the solution, the agitation (or mixing) of the solution, and the surface area of the solute. If any of these three factors change, the rate of dissolution changes. © Accelerate Learning Inc. - All Rights Reserved

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In an unsaturated solution (A), more solute can dissolve in the solvent. In a saturated solution (B), no more solute will dissolve in the solvent. In a supersaturated solution (C), additional solute has precipitated out of the solution to form crystals.

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STEMscopedia: SOLUTIONS Surface Area: When the surface area of a solute increases, the dissolution rate also increases. Suppose you had a spoonful of sugar granules and the same amount of sugar pressed into a cube. The spoonful of sugar has a greater total surface area than the cube because each granule in the spoonful contacts the solvent separately. So the spoonful of sugar will dissolve at a faster rate than the sugar cube. A spoonful of sugar granules (left) has a greater surface area than sugar cubes (right) as well as a faster dissolution rate.

Solution Temperature: Heating a solution causes the particles in the solution to move more rapidly. As a result, the solvent and solute particles collide more frequently and with greater force. Therefore, when the temperature of a solution increases, the rate of dissolution increases. Lemonade mix dissolves more quickly in hot water than in cold water. Agitation: Agitating a solution increases dissolution rate. If you stir lemonade mix into water, the mix will dissolve more quickly. A washing machine spins as it cleans your clothes to help the detergent dissolve faster in the water.

Connecting With Your Child Experimenting with Solubility To help your child learn more about the factors that affect solubility and the rate of dissolution, perform the following experiments together. Materials: • 6 sugar cubes • 2 glasses • measuring cup • spoon • water (warm and cold) • thermometer • stopwatch

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STEMscopedia: SOLUTIONS Your child will observe what happens in three different scenarios and compare the results of each set of experiments. Experiment 1 Your child should pour one cup of warm water into one glass and one cup of cold water into a second glass. After recording the water’s temperature in each glass, add one sugar cube to each glass at the same time and start the stopwatch. Your child should record which sugar cube dissolves faster. Experiment 2 Pour one cup of water at the same temperature into two separate glasses. Crush one of the sugar cubes into smaller pieces. Then add the crushed pieces to one glass of water and a complete sugar cube to the other glass at the same time and start the stopwatch. Your child should record which sugar sample dissolves faster. Experiment 3 Pour one cup of water at the same temperature into two separate glasses. Then add one sugar cube to each glass at the same time and start the stopwatch. Your child should stir the solution in one glass gently with the spoon, but leave the solution in the other glass unstirred. Record which sugar cube dissolves faster. Data: Experiment # 1 1 2 2 3 3

Solvent warm water cold water identical temperature identical temperature identical temperature identical temperature

Solute sugar cube sugar cube sugar cube

Time To Dissolve

crushed sugar cube sugar cube (untouched) sugar cube (gently stirred)

Here are some questions to discuss with your child: 1. In each separate experiment, which sugar dissolves faster? Explain why. 2. How is the rate of dissolution different from the solubility of a substance? How could you test the solubility of a solution? 3. Combining all of the data, what methods can you use to minimize the dissolving time of a sugar cube? Explain.

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PS6ABC Solutions

Reading Science Name:

Date:

Group:

Solubility and Nutrients 1

The human body is an open system, and a constant exchange of nutrients and energy occurs between the body and its surroundings. Food is eaten to provide the energy that is stored in the molecular structure of the food molecules. Food is first broken down in the stomach and then passes through the intestinal tract where it is either absorbed or emitted by the body. Once absorbed, the minerals and nutrients pass into the bloodstream, where they are transported to various parts of the body. When they arrive in the proper location, the nutrients are either utilized or reorganized into new molecules. Whether or not the minerals and nutrients are absorbed and where they are absorbed depends on the solubility of those nutrients.

Several factors affect the solubility of the nutrients that we eat. The term solubility means the amount of a substance that dissolves in a given quantity of solvent at specified conditions of temperature and pressure to produce a saturated solution. Remember, a solvent is the dissolving medium in a solution. As the bloodstream is a fluid environment that transports nutrients, the solubility of these nutrients is vital to the well-being of the body.

Some nutrients are water soluble, meaning that they dissolve in aqueous solutions. Other nutrients are fat soluble, meaning they dissolve in fatty tissues and oils. Some nutrients are also solubilized by the proteins that we eat and transported through the bloodstream by the proteins. It is very important that we understand the solubility of various nutrients so that we can understand both how our body uses those nutrients and how often we should eat those nutrients.

Several factors affect nutrient solubility. One of those factors is the temperature of the solution. Temperature is the average kinetic energy of the particles of a substance. The higher the temperature, the faster the particles move. This means that at a higher temperature, there is an increased chance that the solute particles will make contact with the solvent particles, increasing the rate that the solute dissolves. Most of the vitamins and minerals that we eat are soluble at body temperature, or 37ºC. A second factor has to do with the concentration of the solute in the solvent. There needs to be enough solvent to surround the solute particle so that it can be dissolved. This goes for both aqueous and fatty solutions in our bodies.

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PS6ABC Solutions

Reading Science 5

The third, and perhaps most important, factor for the solubility of nutrients has to do with the molecular structure of the nutrients. There is an old saying regarding the rules of solubility: like dissolves like. This means that the structures of “like” substances will dissolve in each other. What does this mean? Molecules can be polar (have a charge) or nonpolar. Polar molecules tend to dissolve in polar solutions, such as water. Nonpolar fatty molecules tend to dissolve in lipids, such as fats.

The vitamins that we eat can be either water soluble or fat soluble. Water soluble vitamins are not stored in the body; therefore, they must be replenished each day as they are washed out with the urine. These vitamins include the B-complex vitamins and vitamin C. On the other hand, fat soluble vitamins become dissolved in fat before entering the bloodstream, and the excess is stored in the liver. These types of vitamins, which include vitamins A, D, E, and K, do not need to be replenished each day as they can be stored in fat tissues within the body.

Why are these important? Vitamin C is a critical antioxidant that aids in the health of cell membranes. The B-complex vitamins aid in metabolism and cell growth and division. Vitamin D aids in the absorption of calcium, an essential mineral. Calcium controls such functions as muscle contraction, nerve impulses, and blood clotting. If the concentration of calcium in our bloodstream (body fluids) gets too low, the calcium must be replenished by food intake or the body will take the necessary calcium from the bones.

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PS6ABC Solutions

Reading Science 1.

Which of the following is not a factor in nutrient solubility? A.

The size of the molecule

The temperature of the solution

The molecular structure of the nutrient

The concentration of the nutrient in solution

The first paragraph discusses why the solubility of nutrients is important to the function of the human body. The solubility of nutrients is important because ____________. A.

whether or not the nutrients are absorbed depends on their solubility

where the nutrients are absorbed depends on their solubility

Both A and B

None of the above

Which vitamin is water soluble, needs to be replenished each day, and is a critical antioxidant? A.

Vitamin A

Vitamin C

Vitamin D

Vitamin E

Which vitamin is fat soluble and aids in the absorption of the essential mineral calcium? A.

Vitamin A

Vitamin C

Vitamin D

Vitamin E

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PS6ABC Solutions

Math Connections Name:

Date:

Group:

Factors That Affect Solubility Part I: Effect of Temperature on Solubility Effect of Temperature on the Solubility of Solids

Effect of Temperature on the Solubility of Gases

The graph on the left shows the effect of temperature on the solubility of several solids. Write a general rule to describe the graph above.

What do you notice about the effect of temperature on the solubility of NaCl? Does the rule you constructed above apply to every solid?

The graph on the right shows the effect of temperature on the solubility of several gases. Write a general rule to describe the graph above. Does the rule apply to all gases shown in the graph?

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PS6ABC Solutions

Math Connections Part II: Effect of Pressure on Solubility

The amount of pressure put on a solution has little effect on the solubility of liquids and solids. However, pressure greatly affects the solubility of gases. Henry’s law states that the solubility of a gas in a liquid at a given temperature is directly proportional to the partial pressure of the gas over the solution. In other words, Solubility = k x P where the constant k is a characteristic of a specific gas and P is the partial pressure of the gas over the solution. Conversion factor: 1 atm = 760 mmHg Use this information to solve the problems below.

The Henry’s law constant of methyl bromide (CH3Br) is k = 0.159 mol/(L x atm) at 25oC. Calculate the solubility (in mol/L) of methyl bromide in water at 25oC at varying partial pressures in the chart below. Show your work on a separate sheet of paper. Partial Pressure (mmHg) 100 200 300 400 500

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Partial Pressure (atm)

Solubility (mol/L)

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PS6ABC Solutions

Math Connections Part II: Effect of Pressure on Solubility, continued 5.

Plot the data on the graph below.

Solubility in mol/L

Effects of Pressure on Solubility of Gases

Partial Pressure in atm 6.

Write a general rule to describe the effect pressure has on the solubility of gases.

Create an equation to describe the graph using the y=mx+b form. What does y represent? What does x represent? What is the slope of the line? Is there a y-intercept?

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PS6ABC Solutions

Math Connections Part III: Determining Saturation of a Solution

A solution consists of a solvent and one or more solutes in various concentrations. A solvent is the substance in which the matter is dissolved. A solute is the matter that is being dissolved. In a saltwater solution, the water is the solvent and the salt is the solute. We can classify solutions by comparing their ratio of solute to solvent. A saturated solution occurs when the maximum possible amount of solute is dissolved in a particular amount of solvent at a certain temperature. An unsaturated solution occurs if the solution contains less than the maximum possible amount of dissolved solute. A supersaturated solution occurs if the solution contains more than the maximum possible amount of dissolved solute. The solubility curve to the right indicates how much solute can be dissolved in water at various temperatures. Use the solubility curve to help you solve the following problems.

In 100 g of H2O at 50oC, what amount of NH4Cl will make a saturated solution?

In 25 g of H2O at 80oC, what amount of NaCl will make a saturated solution?

10. In 20 g of H2O at 5oC, what amount of Na2SO4 will make a saturated solution?

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PS6ABC Solutions

Math Connections Part III: Determining Saturation of a Solution, continued 11. Determine whether the following solutions are saturated, supersaturated, or unsaturated: a)

46 g of KClO3 is dissolved in 200 g of H2O at 50oC. ___________________________

30 g of KCl is dissolved in 50 g of H2O at 60oC. ______________________________

115 g of NaNO3 is dissolved in 100 g of H2O at 20oC. __________________________

64 g of NaCl is dissolved in 200 g of H2O at 30oC. _____________________________

12 g of NH3 is dissolved in 50 g of H2O at 50oC. ______________________________

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PS6ABC Solutions

Writing Science Name:

Date:

LOOK

THINK The amount of dissolved sugar in tea is determined by its temperature. There are many factors that influence the solubility of a solute dissolved in a solution. Temperature, agitation, and surface area are all related to how much solute a solvent is able to carry in solution. An increase in temperature, agitation, and surface area will usually increase the rates of dissolution. However, the ability of a gas to dissolve in a liquid will actually decrease in higher temperatures. Solids, liquids, and gas solutes may dissolve in other solids, liquids, and gaseous solvents. Although usually the solvent will be liquid water, sometimes it is possible for a solid to be the solvent. Rarely a gas can act as the solvent. Gas, however, is often found only as a solute. Soft drinks are a good example of a gas dissolved in a liquid or solvent. WRITE What temperature would be required to produce the sweetest tea possible? Limit your response to very hot, moderate, or very cold, and justify your answer. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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PS6ABC Solutions

Writing Science Topic:

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Physical Science

PS6DE

Acids and Bases

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PS6DE Acids and Bases

Student Handout Name:

Date:

Procedure 1. Take the pipet filled with invisible ink and write a word on the paper. Make observations over the next 30 seconds.

Write another word and immediately begin to blow on the ink. Record your observations.

Get a cotton ball and slightly dampen it with vinegar.

Write a third word on the paper and dot the ink with the vinegar. Record your observations.

Get a cotton ball and dip it in the ammonia.

Wipe the ammonia cotton ball over each of the three words you wrote on the paper. Record your observations.

a. Word one: _____________________________________________________________ ________________________________________________________________________ b. Word two: ______________________________________________________________ ________________________________________________________________________ c. Word three: ____________________________________________________________ ________________________________________________________________________ Using the pH scale on the Teacher Handout, what can you conclude about the ink before it touched the air and after it touched the air?

Using the pH scale, what can you conclude about the ammonia?

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PS6DE Acids and Bases

Student Journal Name:

Date:

Group:

Part I: Acids and Bases Record your observations below. Substance Name

Physical Properties

pH?

Acid, Base, or Neutral

distilled water

tap water

baking soda dissolved in water

ammonia

white vinegar

lemon juice

two drops of lemon juice and two drops of distilled water

two drops of vinegar and two drops of ammonia

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PS6DE Acids and Bases

Student Journal Part II: Common Household Substances Procedure 1. Plan an investigation to determine the pH of the substances on the table. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 2. Fill in the data table below once the items have been tested by the class. Acids Substance

Bases pH

Substance

What pattern do you observe in the data table?

_______________________________________________________________________________ _______________________________________________________________________________

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Student Journal

PS6DE Acids and Bases

Part III: Acid and Base Structure Write a brief summary of the relationship between the structure and the properties of acids and bases. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

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STEMscopedia: ACIDS AND BASES PS6DE Reflect Some flowering plants show variations in their flower color depending on soil conditions. Consider hydrangeas, shown in the photos below. When grown in acidic soil, hydrangeas tend to produce blue flowers (left). When grown in basic soil, hydrangeas produce pink flowers (right).

What is the difference between acidic and basic soil? Why does this influence flower color in hydrangeas? Chemists classify some chemical compounds as acids or bases. The terms acidic and basic are used when describing solutions or substances. These terms imply the presence of compounds known as acids or bases. Acids and bases are two classifications of chemical compounds. A compound is classified as an acid or a base based on its chemical properties. The first scientist to recognize and describe acids and bases was the Swedish chemist Svante Arrhenius. In the late 1800s, Arrhenius defined acids and bases as follows: Arrhenius acid: a substance that dissociates to form hydrogen ions (H+) in water Arrhenius base: a substance that dissociates to form hydroxide ions (OH-) in water An example of an Arrhenius acid is hydrochloric acid (HCl). When placed in water (H2O), hydrochloric acid dissociates—or breaks apart—to form hydrogen ions (H+) and chloride ions (Cl-): H2O HCl → H+ (aq) + Cl- (aq) An example of an Arrhenius base is sodium hydroxide (NaOH). When placed in water, sodium hydroxide dissociates to form sodium ions (Na+) and hydroxide ions (OH-): H2O NaOH → Na+ (aq) + OH- (aq) The scientific definitions for acids and bases have changed over time. According to Arrhenius’s definition, only substances that release hydrogen ions may be classified as acids. Likewise, only substances that release hydroxide ions may be classified as bases. However, later scientists found many substances that do not fit these definitions, yet still have properties that are similar to either acids or bases. In 1923, two scientists each independently proposed new definitions to describe acids and bases. A Danish chemist, Johannes Brønsted, and an English chemist, Thomas Lowry, introduced the following definitions:

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STEMscopedia: ACIDS AND BASES Brønsted-Lowry acid: a substance that donates hydrogen ions Brønsted-Lowry base: a substance that accepts hydrogen ions For example, hydrochloric acid acts as an acid, according to the Brønsted-Lowry definition, because it donates hydrogen ions to water. Water in this case acts as a Brønsted-Lowry base. It accepts hydrogen ions to form hydronium ions (H3O+): HCl + H2O → Cl- + H3O+ (acid) (base) Ammonia (NH3) acts as a Brønsted-Lowry base because it accepts hydrogen ions from water to form ammonium ions (NH4+). Because water donates hydrogen ions in this case, water acts as a BrønstedLowry acid: NH3 + H2O → NH4+ + OH(base) (acid) From the Brønsted-Lowry definitions, you can infer that acids and bases behave in pairs so that there is always an acceptor and a donor of hydrogen ions. This is an important point because it highlights the differences between the Arrhenius and Brønsted-Lowry definitions. Water behaves as a BrønstedLowry base in the example involving hydrochloric acid, above, and as a Brønsted-Lowry acid in the example involving ammonia. Water would not be classified as an acid or a base according to the Arrhenius definition. Water can behave as both an acid and a base. In the examples of Brønsted-Lowry acids and bases shown above, water acted as a donor of hydrogen ions in some situations and as an acceptor in other situations. This property of water allows it to behave as both an acid and a base, depending on the circumstances. Water is said to be amphoteric because it can be classified as both an acid and a base. In fact, water demonstrates both acidic and basic properties when it reacts with itself, as shown below:

Two molecules of water (H2O) react to form ions of hydronium (H³O+) and hydroxide (OH-). Similarly, a hydronium ion and a hydroxide ion react to form two water molecules. These reversible reactions happen continually in water.

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STEMscopedia: ACIDS AND BASES Acid-base reactions are different from other reaction types. The Brønsted-Lowry deﬁnitions provide a basis for distinguishing acid-base reactions from other types of reactions. According to Brønsted-Lowry deﬁnitions, acid-base reactions involve the transfer of hydrogen ions from an acid to a base. To classify a reaction as an acid-base reaction, look for the movement of H+ from one reactant to the other. Here is an example of such a reaction: HCl + NaOH → NaCl + H2O In this reaction, a hydrogen ion moves from hydrochloric acid (HCl) to sodium hydroxide (NaOH), producing sodium chloride (NaCl)—a salt—and water (H2O). This is another distinguishing feature of acid-base reactions. An acid-base reaction produces water and a salt. Although you are likely most familiar with sodium chloride, or table salt, there are many other salts, including potassium chloride (KCl), potassium iodide (KI), and calcium iodide (CaI2). Acid-base reactions share some similarities with precipitation reactions. Both types of reactions are examples of double replacement reactions, which occur whenever two ionic compounds exchange cations in a solution. However, the product of a precipitation reaction is an insoluble precipitate. No insoluble precipitate is formed in an acid-base reaction. Water is formed instead. Acid-base reactions also share some similarities with oxidation-reduction (redox) reactions. Acid-base reactions always involve an acid-base pair of reactants, but only oxidation-reduction reactions always involve a reacting pair consisting of an oxidizing agent and a reducing agent. However, there is no exchange of electrons between reactants in an acid-base reaction—only an exchange of protons (H+ ions). In contrast, oxidation-reduction reactions involve the transfer of electrons between reactants.

What Do You Think? Which of the following reactions is an acid-base reaction? You can check your answer on the next page. Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g) HF(aq) + KOH(aq) → KF(aq) + H2O(l) HCl(aq) + AgNO3(aq) → HNO3(aq) + AgCl(s) The acidity of a solution is measured using pH. The term acidity is used to describe the concentration of hydrogen ions in a solution. The greater the acidity of a solution, the greater its concentration of hydrogen ions. The actual concentration of hydrogen ions in any solution—even one that is very acidic—tends to be low. Concentrations are often measured in ranges of 10−1 to 10−14 moles per liter. Because of this, a quantity called pH was developed to describe hydrogen ion concentrations. pH is deﬁned as the negative logarithm (base 10) of the hydrogen ion concentration [H+]:

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STEMscopedia: ACIDS AND BASES pH = −log[H+] You can use this equation to insert a value for the concentration of hydrogen ions in a solution and solve for pH. The table below shows a few examples. Notice that the pH value in each case corresponds to the numerical value of the exponent in the concentration value: pH [H+]

1 1 X 10-1 M

2 1 X 10-2M

3 1 X 10-3M

4 1 X10-4M

5 1 X 10-5M

You can see from the trends in numbers that pH increases as hydrogen ion concentration decreases. The more acidic a solution is, the lower its pH. The pH scale shown below organizes the pH values most often used in chemical systems. This scale ranges from the most acidic solutions (low pH = 1) to the most basic solutions (high pH = 14). In the middle of the scale is a neutral zone (pH 7) that is neither acidic nor basic.

The pH scale is used to describe the concentration of hydrogen ions (H+) in a solution. Acidic solutions such as battery acid and lemon juice have high concentrations of H+, whereas basic solutions such as ammonia and lye have low concentrations.

Acids and bases also have different properties. Look at the chart below to see how acids and bases differ. Acid

Base

How do they taste? Sour Bitter How do they feel? Corrosive, burn Slippery Common household product Lemon juice Baking soda pH range 0-6.9 7.1-14 Litmus indicator paper color Red/pink Blue Remember, base starts with a B and a lot of its characteristics also start with B’s.

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STEMscopedia: ACIDS AND BASES Look Out Hydrogen ions do not exist freely in aqueous solutions. Rather, they associate with water molecules to form hydronium ions, which have the chemical formula H3O+. However, chemists often refer to hydrogen ions, particularly when talking about pH. When chemists talk about hydrogen ions, they are really talking about hydronium ions. Acid strength is not measured in pH. Acid strength is an inherent characteristic of any acid regardless of its concentration. A strong acid can have a high pH if it is diluted and a low pH if it is concentrated. Similarly, a weak acid can have a high pH if it is diluted and a low pH if it is concentrated. Therefore, you cannot use pH as a measure of the strength of an acid.

What Do You Think? Which of the following three reactions is an acid-base reaction? An acid-base reaction always produces water and a salt. 1. I2 + 2NaCl → 2NaI + Cl2 2. HF(aq) + KOH(aq) → KF(aq) + H2O(l) 3. 2Al(NO3) + 3CaCl2 → 2AlCl3 + 3Ca(NO3)2 Only the second reaction does this: KF → Salt

H2O → Water

In this reaction, hydrogen fluoride (HF) donates a hydrogen ion to potassium hydroxide (KOH), producing potassium fluoride (KF)—a salt—and water (H2O). Everyday Life You can find examples of acids and bases in your home. The pH scale shown above lists a number of substances that you may be familiar with. Various foods—including citrus fruits, vinegar, and soda—are acidic. Household cleaning products tend to be basic. Examples include soap, ammonia, lye, and bleach. Hydrogen ion and hydroxide ion concentrations in aqueous solutions are related by a constant. So far, we have discussed solutions in terms of their hydrogen ion concentration or pH. In cases of solutions made using water as the solvent, it is also possible to talk about the solutions in terms of their hydroxide ion concentration. This is because water undergoes a reversible reaction in which it dissociates to form a hydrogen ion and a hydroxide ion: H2O ←→ H+ + OH-

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STEMscopedia: ACIDS AND BASES The concentrations of hydrogen and hydroxide ions multiplied together equal the ion product constant for water: Ion product constant = 1X10-14M = [H+][OH-] You can use this equation to calculate the hydroxide ion concentration if you know the hydrogen ion concentration or pH of a solution. Conversely, if you know the hydroxide ion concentration, you can use it to calculate the hydrogen ion concentration and pH of a solution.

What Do You Think? Fill in the chart below with the correct pH or pOH values and determine if the substance is an acid or a base based on the pH value.

pH 2

[H+] 1X10-2M

pOH 12

[OH-] 1X10-12M 1X10-3

Acid or Base Acid

1X10-10M 6 Label the following as an acid (A) or base (B) 1. Feels slippery ________________ 2. Turns litmus paper blue _____________ 3. Tastes sour ____________ 4. Ranges from 0-6.9 on the pH scale _____________ 5. Turns litmus paper red __________________

Reflect Now that we have defined acids, bases, and pH, we can return to the question raised at the beginning of this companion. Recall that hydrangeas produce blue flowers when grown in acidic soil but produce pink flowers when grown in basic soil. So why does soil acidity influence hydrangea flower color? A colored pigment present in the cells in hydrangea flower petals provides color. The pigment molecule is a weak acid. In the acid form (abbreviated below as HA), the molecule has a blue color. In the basic form (abbreviated as A-), the molecule has a pink color: HA+ H2O → A- + H3O+ Blue Pink Because this pigment is a weak acid, it can shift between its blue and pink forms depending on pH. The presence of aluminum ions also tends to stabilize the blue acid form. When planted in soils of low pH, hydrangea plants are better able to take up aluminum ions from the soil. As these ions accumulate in the petals, they shift the pigment to the acid (or blue) form. Soils of high pH inhibit the plants from taking up aluminum, resulting in a shift toward the pink form of the pigment.

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STEMscopedia: ACIDS AND BASES Connecting With Your Child Make Homemade pH Paper To help your child learn more about the concepts of acids, bases, and the pH scale, follow these directions for making and testing pH-sensitive paper. First, prepare red cabbage dye: 1. Cut two leaves of red cabbage into small squares, and puree in a blender with one cup of tap water. 2. Transfer the liquefied cabbage leaves to a small saucepan. 3. Repeat the step above several times until the saucepan is half full. 4. Heat the cabbage leaf puree to boiling on the stove. 5. Reduce the temperature to medium and allow the liquid to simmer 20 minutes uncovered. 6. Cool the liquid to room temperature, then pass it through a coffee filter to remove solid plant material. 7. Collect the filtrate to make pH-sensitive paper in the next step. Next, make pH-sensitive paper: Gather the following materials: • Several sheets of blank white copy paper • Large tray that can hold one sheet of paper • Spoon • Roll of paper towels • Newspaper 1. Pour enough of the cabbage filtrate into the tray so that a sheet of paper is covered with liquid. 2. Carefully add one sheet of paper to the liquid. 3. Press the paper with the spoon so that it becomes covered with liquid. 4. Soak the paper for at least five minutes, then lift it out and place it on paper towels that have been layered over newspaper. 5. Repeat to make several sheets of pH-sensitive paper. 6. Allow the papers to dry. Test your pH-sensitive paper to see how its color reacts when exposed to acids and bases. Acids to try include vinegar, lemon juice, and soda. Bases to try include baking soda, ammonia, and window cleaner. You can make a liquid slurry of baking soda and water by adding some of the powder to a small bowl, adding water, and stirring. Dilute vinegar, lemon juice, ammonia, and window cleaner with water to cut down on fumes and odors. Try using a paintbrush dipped in each solution to transfer some of the acid or base to the pH-sensitive paper.

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STEMscopedia: ACIDS AND BASES Here are some questions to discuss with your child during the testing portion of this activity: 1. What color is associated with acidic conditions? What color is associated with basic conditions? 2. How could you use your pH paper to test whether an unknown substance is an acid or a base? 3. Is the compound that you extracted from cabbage leaves itself an acid or a base?

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PS6DE Acids and Bases

Reading Science Name:

Date:

Group:

The Strength of Acids and Bases 1

You are most likely familiar with the terms acid and base. Hydrochloric acid is a solution that many students have worked with in high school. Sodium hydroxide is a common base. You have also studied chemical reactions and equations. No doubt you are familiar with acid-base reactions, in which an acid and a base are combined, producing water and a salt. However, have you ever wondered what an acid and a base really are? Do you know why they react with other compounds in the ways that they do? Protons are the positive hydrogen ions associated with the acids, or the H+ ions. These protons may react with the hydroxide ions (OH-) of the base, producing water as a result. When acids and bases react with other compounds, what you are observing in those reactions is simply a transfer of protons.

Acids and bases have specific properties based on their chemical structures and arrangements. In the beginning, acids and bases were categorized by taste. Acids had a sour taste, and bases had a bitter taste. In 1884, a scientist named Svante Arrhenius discovered that all acids contained H+ ions and all bases contained OH- ions. Therefore, he concluded that an acid was any solution that contained more H+ than OH- ions. A base was defined as any solution that contained more OH- ions than H+ ions. This became the Arrhenius rule for distinguishing acids from bases.

In 1923, this definition was modified when two scientists, Johannes Brønsted and Thomas Lowry, independently made the same discovery. Their tests found that during an acid-base reaction, a proton was actually transferred from the acid to the base. They defined an acid as a proton donor and a base as a proton acceptor. This meant that any compound that donated a proton could be considered an acid, and any compound that accepted a proton could be a base. This became the Brønsted-Lowry rule for distinguishing acids from bases.

Acids and bases may be strong or weak. What does this mean? A strong acid is an acid that releases all of its hydrogen ions in solution, while a weak acid does not. There are very few true strong acids and many weak acids.

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PS6DE Acids and Bases

Reading Science 5

A strong base is a base that completely ionizes in solution, while a weak base does not. How strong or weak these compounds are can be determined, in part, by the pH level of the solution. The pH scale is a scale ranging from 1 to 14 that measures the concentration of hydrogen ions in a solution. A strong acid will have a pH reading of 1. A strong base will have a pH reading of 14. A neutral solution will have a pH reading of 7.

If we use the Brønsted-Lowry definition of acids (and bases), a strong acid will more easily lose its protons than a weak acid. Furthermore, a strong base will more likely attract protons than a weak base. Strong acids include compounds such as hydrochloric acid, or HCl. This acid will completely dissociate in solution, leaving H+ ions and Cl- ions. This acid is “happier” when it is dissociated into ions in solution. A common weak acid is acetic acid, the acid found in vinegar. This acid, CH3CO2H, will only partially dissociate in solution, leaving some H+ ions and some CH3CO2- ions. This acid is “happier” when it is an acid in solution. Therefore, in solution, strong acids tend to be ions, and weak acids tend to be acids.

So what does this have to do with strong and weak bases? Each acid has something called a conjugate base. The conjugate base of HCl is Cl-. The conjugate base of CH3CO2H is CH3CO2-. The strong acid HCl has a weak conjugate base of Cl-. Why? Remember that HCl prefers to be dissociated into ions in solution. So each time a Cl- ion is present in solution, it is very unlikely that it will accept an H+ ion. Therefore, Cl- has a weak attraction for protons, making it a weak base. On the other hand, the CH3CO2- ion is a strong base, as its conjugate acid prefers to be an acid in solution. This means that the CH3CO2- ion has a strong attraction for protons, making this ion a strong base. In general, the stronger the acid, the weaker its conjugate base, and vice versa.

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PS6DE Acids and Bases

Reading Science 1.

The second paragraph discusses one of the first scientific ways to distinguish acids from bases, known as the Arrhenius rule. According to this rule, what would be considered an acid? A.

Any solution with more H+ than OH-

A proton donor

Any solution with more OH- than H+

A proton acceptor

H2SO4, sulfuric acid, is considered a strong acid. How would you categorize its conjugate base, SO42-? A.

A strong base

A weak base

An Arrhenius base

A Brønsted-Lowry base

According to this definition, a substance that can donate a proton (H+) is considered an acid and a substance that accepts a proton is considered a base. What is this definition known as? A.

Arrhenius definition

Brønsted-Lowry definition

Neutralization definition

Dissociation definition

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PS6DE Acids and Bases

Reading Science 4.

When a compound dissolves in an aqueous solution, the compound may not dissociate completely and form ions in the solution. If a compound dissociates completely to release all of its hydrogen ions in aqueous solutions, what does it form? A.

A strong acid

A strong base

A weak base

Both A and C

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PS6DE Acids and Bases

Math Connections Name:

Date:

Group:

Acids and Bases Part I: Acidity with Arrhenius and Brønsted-Lowry Theories

Compounds can be defined as acids or bases based on their characteristics and based on how the molecules of the compound act when placed into water. Several scientists have developed their own definitions for acids and bases. In the late 1800s, Arrhenius defined acids and bases in aqueous solutions. Arrhenius acid: An ionic compound that ionizes in an aqueous solution and produces hydrogen ions (H+). HCl

H+(aq) + Cl-(aq)

Arrhenius base: An ionic compound that ionizes in an aqueous solution and forms hydroxide ions (OH-). NaOH

Na+(aq) + OH-(aq)

However, later scientists found many substances that do not fit these definitions, yet still have properties of either acids or bases. In 1923, a Danish chemist named Johannes Brønsted and an English chemist named Thomas Lowry independently proposed new definitions to describe acids and bases. Brønsted-Lowry acid: a compound that donates a proton (hydrogen ion H+) Brønsted-Lowry base: a compound that accepts a proton The ion or molecule remaining after an acid has lost a proton is known as the conjugate base, and the species created when a base accepts a proton is known as the conjugate acid. HCl + H2O

acid

conjugate base

NH3 + H2O

NH4+ + OH-

base

conjugate acid

HCl donates a proton to water NH3 accepts a proton from water

Write a balanced equation for the dissociation of each of the following Brønsted-Lowry acids in water. Determine the conjugate base of each acid.

H2SO4

HNO3

H3O+ + Cl-

Label the Brønsted-Lowry acids and bases and show the direction of the proton transfer. OH- + H3O+

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PS6DE Acids and Bases

Math Connections Part II: The pH Scale

The pH of a solution or substance is the number used to describe the hydrogen ion concentration of that solution or substance. The pH scale is a range that goes from 0 to 14. pH 0 7 14

Classification Highly acidic Neutral Highly Basic

Description High H3O+ ion concentration H3O+ ion and OH- ion concentration are equal. High OH+ ion concentration

The pH scale is used to determine the strength of an acid or base. The letter p means “negative logarithm of.” Thus, pH is the negative log (base 10) of the hydrogen ion (H3O+) concentration, and pOH is the negative log of the hydroxide ion (OH-) concentration.

pH = -log [H3O+]

pOH = -log [OH-]

pH + pOH = 14 Example: •

HCl has a [H3O+] concentration of 1 x 100 M and a [OH-] concentration of 1 x 10-14 M.

pH = -log(1 x 100 M) = 0 (strong acid)

pOH = 14 – pH = 14 – 0 = 14

•

NaOH has a [H3O+] concentration of 1 x 10-14 M and a [OH-] concentration of 1 x 100 M.

pOH = -log(1 x 100 M) = 0

pH = 14 – pOH = 14 – 0 = 14 (strong base)

Calculate the pH of an aqueous ammonia solution that has an [OH-] concentration of 3.9 x 10-3 M. Is the solution more basic or acidic?

Step 1: Set up the equation.

pOH = -log[OH-] = -log(3.9 x 10-3)

Step 2: Solve for pH.

pH + pOH = 14

Calculate the pH of a sample of seawater that has an [OH-] concentration of 2.54 x 10-6 M.

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PS6DE Acids and Bases

Math Connections Part II: The pH Scale, continued 5.

Calculate the concentrations of H3O+ and OH- in baking soda (pH 8.3).

Step 1: Adjust the pH equation to solve for the concentration of [H+] ions. pH = -log[H3O+] -pH = log[H3O+] 10-pH = 10log[H3O+] (Remember 10logx = x) 10-pH = [H3O+] Step 2: Substitute pH into the equation and solve for concentration. [H3O+] = 10-8.3 = _____________ Step 3: Solve for the pOH. Remember pH + pOH = 14.

Step 4: Substitute pOH into the equation and solve for concentration.

[OH-] = 10-pOH = __________________ 6.

Calculate the concentrations of H3O+ and OH- in lemon juice (pH 2.0).

Calculate the pH of a 0.20 M solution of NaOH. Is the solution basic or acidic? NaOH

Na+ + OH-

Step 1: Since NaOH dissociates completely, the moles remain proportional, therefore: pOH = -log[0.20]

pOH= ________________

Step 2: Solve for the pH.

pH + pOH = 14

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PS6DE Acids and Bases

Writing Science Name:

Date:

LOOK

THINK You can use pH indicators to create certain colors of solutions. A change in pH will also create different colors. The hydrogen-ion concentration of a substance can be used to calculate pH, and pH can be used to determine the acidity or alkalinity of a solution. The pH scale begins with a 0, which indicates acid and continues through to 14, which indicates a base. The center point of the pH scale is neutral. We use pH indicators to visually observe the pH of a solution. These indicators come in various colors and will change specific colors when exposed to a specific range in pH. If a solution contains a pH indicator and displays a certain color, the color may be changed by adding either an acid or a base. WRITE Explain the chemistry behind the demonstration (often seen in television commercials) in which a colored solution can change colors when another colorless solution is added. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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PS6DE Acids and Bases

Writing Science Topic:

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Physical Science

PS7A

Explaining Energy Transformations in a System

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PS7A Explaining Energy Transformations in a System

Student Journal Name:

Date:

Group:

Energy Transformations PBL Entry Document Your school district has partnered with another district to come up with supplemental aids to help students prepare for their next test. Your class has been chosen to make a review game to help eighth graders understand the concept of energy transformations. Your team has been asked to come up with a board game or electronic game that quizzes the eighth graders on energy transformations. For your game to be considered, you will need to adhere to the following rules. (1) The game must have 10 different energy transformations within a system. (2) The energy transformations must be represented by pictures and arrows only. (3) Answers to the energy transformations must be hidden from initial view. (4) The game needs to be displayed on paper as a board game or electronically in a game template. (5) Three of the energy transformations must show more than one transformation change. (6) One of the energy transformations needs to involve nuclear energy. Your team will have time to research, develop your plan, and create your model. You will present your ideas to an audience in a 3-minute presentation. Divide your team into the following roles to complete the project: team leader, game designer, researcher, and advertiser. Thank you in advance for your effort in helping us increase our test scores.

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PS7A Explaining Energy Transformations in a System

Student Journal Energy Transformations PBL Expert Roles Team Leader As the team leader, you are responsible for ensuring that your team successfully completes the task on time. You will lead and keep track of all planning, encourage communication among your team’s experts, and make sure every team member fully understands all parts of the plan. You and your team members will present your final design in a 3-minute presentation, during which you must state the problem in your own words. Researcher As the researcher, you are responsible for exploring and researching the problem. You will work cooperatively with your team, research any needed information, and help brainstorm and diagram solutions to the problem. After selecting the best design, be sure to get approval from your teacher before proceeding. Game Designer As the game designer, you are responsible for brainstorming and designing a paper game board or interactive digital game. You will need to communicate with your team to identify what materials you will use. You may want to create some diagrams or sketches of your approach and brainstorm with other teams during this process. Build, test, and analyze your design, and make sure to communicate the reasons behind choosing materials and how you will determine if your design is effective. Improve, redesign, and retest as necessary. If your design is not effective, determine what changes need to be made to your game. Advertiser As the advertiser, you are responsible for presenting and sharing your solution to the problem. You will need to communicate how you will share your presentation. You can use brochures, PowerPoint slides, etc. Determine what each team member will contribute to the presentation and how you will handle the classroom discussion.

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STEMscopedia: EXPLAINING ENERGY

TRANSFORMATIONS IN A SYSTEM

PS7A

Reflect Has your cell phone ever died right when you needed to take a picture? What did you have to do? Charge it! Once you plug it into the charger, it seems like you have instant energy. Sometimes energy may seem to come out of nowhere, or we may do something that seems to create energy, such as plugging in the charger. On the other hand, sometimes energy may seem to disappear, or we may do something that seems to destroy energy. In fact, none of these things actually happens.

Energy is neither created nor destroyed. This statement is the law of conservation of energy. The law of conservation of energy is true throughout the universe! The same amount of energy that exists now has always existed. It is constantly changing form, but it never increases or decreases. Scientists usually deﬁne energy as the ability to do work. That makes sense because you can’t get much work done if you’re low on energy. There are many forms of energy, including electromagnetic, light, sound, electrical, thermal, chemical, nuclear, and mechanical. Most of these types involve kinetic energy, or energy of motion. •

The electromagnetic spectrum shows the types of electromagnetic energy from long to short wavelengths.

Electromagnetic energy is energy that travels in a wave form through space. This energy includes all the parts of the electromagnetic spectrum. Radio, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays are all electromagnetic energy. •

•

Light energy is a special form of electromagnetic energy. This is the one form of energy we can actually Sound is the weakest form see. of energy. • Sound energy is vibrations that move through objects in a wave-like motion. Sound requires matter in Light energy can be order to travel. This is why sound will generated through not travel in a vacuum, like space. chemical reactions. There is an absence of particles to vibrate! Electrical energy is the flow of electrons (negatively charged particles) through a conductor. When we control Lightning and static shocks are natural electrical energy, we call that electricity. examples of electrical energy.

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•

Thermal energy is the sum of the motion of the particles within an object. The higher the temperature, the faster the particles are moving and the more thermal energy the object has. Sometimes, this is also called heat energy. However, heat is when the energy is in transit during convection, conduction, and radiation.

Objects contain thermal energy, not heat. This iceberg has a large amount Chemical energy and nuclear energy are both types of potential energy, or stored of thermal energy even energy. though it is cold. •

Chemical energy is stored in the bonds between atoms. When these bonds are broken, the energy is released.

•

Nuclear energy is stored in the nucleus of an atom. Although atomic nuclei are small, the nuclear energy stored there is very powerful!

•

Mechanical energy is unique in that it is the combination of an object’s motion and position, so it includes both kinetic and potential.

Nuclear power plants use nuclear fission, which is the splitting of a nucleus of uranium to generate electricity.

Food and combustible fuels are examples of chemical energy.

What Do You Think? Energy can change from form one to another within a system. Flashlights and wind turbines are open systems. Energy enters the system in one form (from a battery or the wind) and leaves the system in another form (as light energy or electrical energy). In a closed system, energy does not leave the system, though it may change its form many times. If the energy in one part of a closed system increases, what do you think happens to the energy in another part of the system? Does it increase, decrease, or stay the same? (HINT: The universe is a closed system. As the Sun sends energy to Earth, the amount of energy on Earth increases. According to the law of conservation of energy, what must be happening to the amount of energy in the Sun?) system: an arrangement of parts that work together to perform a task.

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Look Out When energy changes form, it is called an energy transformation. Energy transformations demonstrate the law of conservation of energy. You may wonder how the law of conservation of energy applies to the world around you. Consider this. Energy allows an animal to move faster. Where does the energy of motion come from? Over time, the animal slows down. Where does the energy go? In the instance above, the energy has been transformed. When energy seems to come out of nowhere, it is usually because we are converting a stored form of energy to a form that can do work. When energy seems to be used up, it has usually been changed into a stored form that we cannot easily use. Our bodies are great examples of energy transformation in a system. We eat food to get energy to climb a mountain. The energy is stored in the chemical bonds that make up the food. As we move up and down the mountain, this chemical energy changes to mechanical energy. As we move, we get hot. This is our mechanical energy changing to thermal energy. Climbing the mountain makes the air around us slightly warmer because heat from our bodies is transferring into the air. This increase in thermal energy equals the chemical energy stored in the food we have eaten. Energy is neither created nor destroyed—it simply changes form! The chemical energy (food) is transferred into mechanical energy (hiking), which is transferred into thermal energy (warming air). Another example of an energy transformation in a system is the Sun. In the core of the Sun, nuclear fusion is happening. Nuclear fusion is the fusing, or joining together, of atomic nuclei. As nuclear fusion occurs, the nuclear energy transforms into other energy forms, including thermal, light, and electromagnetic. The light from the Sun then begins a new energy transformation in a different system. The light energy gets captured by chloroplasts in plant cells. That light energy is then transformed into chemical energy in the form of sugar. This energy transformation is called photosynthesis. A television is another example of a system. This system begins by being plugged into an electrical outlet. Anytime an object plugs into an outlet, that system will begin with electrical energy. The electrical energy will flow from the outlet, through the wire, and into the television. Inside the television, the electrical energy transforms to light and sound energy.

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Other system examples include flashlights and wind turbines. Most flashlights are powered by batteries. Batteries contain certain chemicals in which energy may be stored. So the energy stored in batteries is a form of chemical energy. When we use batteries in a flashlight, the chemical energy is transformed into electrical energy. Wires in the flashlight carry the electrical energy to the light bulb. There, the electrical energy is transformed into light energy that we use to see. Electrical energy can also be generated from kinetic energy. This is the transformation that happens in wind turbines. Because wind is the motion of air particles, it is a form of kinetic energy. This energy is transferred to the blades of the wind turbine. The blades (turbine) will turn a generator. A generator is a machine that transforms kinetic energy into electrical energy. Underground wires carry the electricity away from the wind turbines to buildings where people can use it.

Try Now Energy transformations are typically written using arrows. The arrows point from the beginning energy to the new energy. For example, the flashlight transformation from the previous section would be written as: chemical

electrical

light

Match the following transformations with the system they go with. 1. ____ electrical 2. ____ electrical 3. ____ chemical 4. ____ sound 5. ____ mechanical

thermal and light mechanical and thermal thermal electrical sound

A. clothes dryer B. natural gas stove C. acoustic guitar D. toaster E. microphone

Write the energy transformation for the following systems. Remember to use arrows. System 6. burning candle

Transformation

7. solar calculator 8. dam

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TRANSFORMATIONS IN A SYSTEM

Connecting With Your Child Identifying Everyday Energy Transformations With your child, look around your home and neighborhood for examples of energy transformations in a system. It is important to understand how each transformation demonstrates the law of conservation of energy. The goal is to ﬁnd as many types of transformations as possible. The transformation from electrical to other forms of energy is an easy place to start. You should be able to ﬁnd electricity transformed into most of the following forms of energy: • • • • •

Thermal (e.g., toaster, oven, range) Light (e.g., light bulbs, computer monitor, TV screen) Sound (e.g., radio, TV, stereo) Mechanical (e.g., motors in fans, washing machine, blender) Chemical (e.g., battery charger)

You can see kinetic and potential energy—the two components of mechanical energy— being transformed back and forth in any pendulum system, such as a playground swing. There are many examples of chemical energy being transformed into heat, light, and kinetic and potential energy. Any movement by an animal (including people) or use of a combustible fuel transforms chemical energy into at least one other form. Remind your child that people usually want to transform energy into a specific form to do a specific kind of work, but all energy transformations produce energy in unwanted or “wasted” forms as well. The wasted energy is usually transformed into heat. For example, the heat given off by a tungsten filament bulb greatly reduces its efficiency in providing light. An electric stove burner produces some light that reduces its efficiency in providing heat. In general, heat energy is the final result of all series of energy transformations. Unfortunately, this “waste” heat dissipates into the universe and cannot be reused by humans. If you want to tabulate your study of energy-transforming devices, you could use a table like this. (An example is provided.) System Plant (photosynthesis)

Energy Transformation Light

chemical

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TRANSFORMATIONS IN A SYSTEM

Here are some questions to discuss with your child: 1. Compare your body temperature (almost 100 degrees Fahrenheit) to a comfortable room temperature. What does this tell you about how your body transforms the chemical energy stored in food? 2. When the chemical energy in gasoline is transformed in the engine of a car, it is eventually transformed into many other forms of energy. What are some examples of the energy transformations that happen in a car? 3. Where in your home does energy appear to be created or destroyed? Use the law of conservation of energy to explain how energy is not actually created or destroyed in each instance.

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Reading Science Name:

Date:

Group:

Flashlights 1

A flashlight is a portable, battery-operated device that produces light. A typical handheld flashlight consists of one or more batteries inside a compartment that forms the handle of the light. There is a switch between the batteries and the bulb. The switch controls the flow of electricity between the batteries and the bulb.

Flashlights have multiple uses. We use them during emergencies, such as power outages or when our car breaks down. Our parents may use them while searching through the attic, the basement, or a dark closet. You may have used one on a camping trip or when you walked down the street while trick-or-treating. Everyone has used a flashlight at one time or another. When we do, energy is transformed.

Energy is the ability to do work or cause a change. The law of conservation of energy states that “energy cannot be created or destroyed; it can only be transformed.” There are many different forms of energy, such as chemical energy, electrical energy, and light energy.

What energy transformations occur when we use a flashlight? First, the batteries contain chemical energy. This is energy that will be released during a chemical change. When chemical bonds are formed or broken, electrons are rearranged. This movement of electrons produces chemical energy. Batteries can convert stored chemical energy into electrical energy.

Electrical energy is the energy of electricity. When electrical charges move through a conductor, it is called electricity. Electricity moves through wires to places where it is needed. Then it can be converted into other forms of energy. In a flashlight, the electrical energy becomes light energy and thermal energy in the bulb.

Light energy moves by wave motion. That is, light is a form of energy caused by electromagnetic waves. It enables us to see, since objects are only visible when they reflect light into our eyes. Our eyes convert the light energy back to electrical energy. They make a nerve signal, which our brain converts into an image that we see.

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Reading Science 7

Thermal energy is the energy of heat. When energy transforms, a small amount is often converted into thermal energy as a byproduct. The bulb transforms electrical energy into both light energy and thermal energy. It makes more light than heat, however. This is why the light bulb starts to feel warm after the flashlight has been on for a while.

The last time you looked at a flashlight, it probably looked pretty simple. You flip the switch, and light comes out. Now you know that there is much more happening. Energy must first be converted from chemical energy in the batteries into electrical energy. This energy then moves to the bulb to be transformed into the light you see.

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Reading Science 1.

Which of the following sentences best summarizes the flashlight? A.

A flashlight has many uses.

A flashlight creates light energy, allowing us to see in the dark.

A flashlight is a necessary tool for every household.

A flashlight is a portable, battery-operated device that makes light.

Much like a battery, wood contains stored energy. What energy transformations occur when wood is burned? A.

Thermal energy transforms to chemical energy and light energy.

Biological energy transforms to electrical energy and light energy.

Chemical energy transforms to thermal energy and light energy.

Chemical energy transforms to thermal energy and heat energy.

What does the word convert mean in the following sentence: “Our eyes convert the light energy back to electrical energy”? A.

Transfer

Change

Transport

Current

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Reading Science 4.

Identify the correct order for the energy transformations in a flashlight. A.

Electrical to chemical to thermal

Light to electrical to chemical

Thermal to electrical to light

Chemical to electrical to light

In an ideal situation in which no heat energy is produced, what is the relationship between the chemical energy provided by the battery and the electrical energy produced according to the law of conservation of energy? A.

The chemical energy should be less than the electrical energy.

The chemical energy should be equal to the electrical energy.

The chemical energy should be more than the electrical energy.

None of the above.

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PS7A Explaining Energy Transformations in a System

Math Connections Name:

Date:

Group:

When energy flow occurs in a system, measureable changes to parts of that system may occur, such as speeding up, slowing down, and getting warmer or cooler. The total amount of energy within the system remains the same, yet the forms of energy can change. A flashlight demonstrates energy transformation when the energy in a battery changes from chemical energy to electrical energy to light energy. The data below show the results from an investigation designed to see whether different brands of batteries store different amounts of chemical energy. To complete the investigation, 10 flashlights with new Bear lithium batteries and 10 flashlights with new Rotar nickel batteries were turned on. The experimenters observed the amount of time each flashlight released light energy and recorded those hours after turning off each flashlight. Flashlights Powered by Batteries Trial Number

Bear batteries (hours) Rotar batteries (hours)

2.5 6.1

5 5.7

3.7 2.4

2.2 3.7

4.1 3.2

3 4.8

2.8 4.33

4.7 6

2 3.6

0.5 2.8

Using the data above, create a box and a whisker plot by following the steps below. 1.

Order each set of data from least to greatest, and calculate the median (known as Q2) number of hours. • Bear lithium batteries: • Rotar nickel batteries: Divide the data in half, and find the median of the first and second halves of the data. •

Bear lithium batteries

• •

First half: Sub-median (known as Q1):

• •

Second half: Sub-median (known as Q3):

•

Rotar nickel batteries

• •

First half: Sub-median (known as Q1):

• •

Second half: Sub-median (known as Q3):

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PS7A Explaining Energy Transformations in a System

Math Connections For future reference, fill in the chart below using data from the first page. Bear Lithium Batteries

Rotar Nickel Batteries

Minimum time Maximum time Median (Q2) Sub-median (Q1) Sub-median (Q3) Use the numberline below to complete steps 3 and 4 for each of the battery types. Both the box plot and the whisker plot will use the same number line.

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Mark off the minimum, maximum, Q1, Q2, and Q3 values on the numberline.

Draw a box from Q1 to Q3, and then extend the “whiskers” to the maximum and minimum values.

Describe the distribution of the two graphs. Consider the interquartile range (the length of the boxes) of the data and where the median lies.

What are the mean, median, mode, and range of the data for each battery type? Bear Lithium Batteries

4.0

4.5

5.0

5.5

6.0

6.5

7.0

Rotar Nickel Batteries

Mean Median Mode Range 7.

What conclusions can you draw about the differences in the brands of batteries?

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PS7A Explaining Energy Transformations in a System

Writing Science Name:

Date:

LOOK

THINK Energy transformations occur all around us. They occur in our bodies and in items seen and used in our everyday lives. For example, energy transformation occurs in the cars we drive and the cell phones we talk on. Energy transformations allow energy to be converted for different uses. Scientists and engineers work to discover more efficient means of converting energy. Advances have been made to produce energy through solar panels and windmills to protect the environment. Many times there are multiple energy transformations taking place within a closed system. WRITE Multiple energy transformations take place when lighting a match. Explain the transformations present when a match is ignited. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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Writing Science Topic:

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Physical Science

PS7BC

Thermal Energy

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PS7BC Thermal Energy

Student Handout Name:

Date:

Where in the picture do you see heat moving?

Conduction is a direct type of heat transfer where two objects are in contact with each other. Where in the picture do you see this happening? (Label and explain.)

Convection is a type of heat transfer that happens in liquids and gases where the movement of heat occurs through a current. Where in the picture do you see this happening? (Label and explain.)

Radiation is a type of heat transfer that happens when heat energy travels through space or the atmosphere. Where in the picture do you see this happening? (Label and explain.)

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PS7BC Thermal Energy

Student Journal Name:

Date:

Group:

Part I: Temperature and Thermal Energy Transfer 1.

What is temperature?

_______________________________________________________________________________ _______________________________________________________________________________ 2.

What is thermal energy?

_______________________________________________________________________________ _______________________________________________________________________________ 3.

How does the temperature of the ice chip compare to the temperature of your hand?

_______________________________________________________________________________ _______________________________________________________________________________ 4.

Draw the molecular structure of the ice.

In the example of holding ice, what evidence indicates that thermal energy transfers?

In the example of holding ice, where does the thermal energy come from?

_______________________________________________________________________________

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Student Journal Part I: Temperature and Thermal Energy Transfer, continued 8.

In the example of holding ice, where does the thermal energy go?

_______________________________________________________________________________ 9.

Explain the molecular motion of the water molecules as the ice melts.

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PS7BC Thermal Energy

Student Journal Part II: Conduction 1.

Data Table: Melting Wax Chips by Conduction Chip

Time 2.

Use the drawing below to illustrate what you observed. Use labels and arrows to identify the transfer of heat.

What type of heat transfer occurs along the aluminum foil? Where exactly does the transfer take place?

_______________________________________________________________________________ _______________________________________________________________________________ 4.

What pattern was evident in the movement of thermal energy?

_______________________________________________________________________________ _______________________________________________________________________________ 5.

What evidence did you observe that showed heat transfer.

_______________________________________________________________________________ _______________________________________________________________________________ 6.

Explain the molecular motion within the foil.

_______________________________________________________________________________ _______________________________________________________________________________

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Student Journal Part III: Convection 1.

Draw a lava lamp and show what happens to the blob you observe. Use arrows and labels to identify the parts of the lamp and the heat transfer.

Draw the can of cooking fuel and what you observed on the wall or board. Use arrows and labels to identity the setup and the heat transfer. Be sure to show where the heat near the ceiling went.

In which state of matter did the transfer of thermal energy occur in the lava lamp?

_______________________________________________________________________________ 4.

In which state of matter did the transfer of thermal energy occur when you observed the cooking fuel?

_______________________________________________________________________________ 5.

Explain the molecular motion in each of the fluids you observed.

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PS7BC Thermal Energy

Student Journal Part IV: Radiation 1.

Record your data in the boxes below. Radiometer at Radiometer at 20 cm 20 cm

Radiometer at 20 cm

Did the vane move?

beginning temperature

temperature after 3 min

Graph the ending temperatures for each location of the radiometer.

Fill in the blanks using the data you recorded. A. B.

As the distance increased, the temperature ________________. As the distance decreased, the temperature _________________.

How is radiation different from convection and conduction? ____________________________ ___________________________________________________________________________ ___________________________________________________________________________

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Student Journal Part V: Specific Heat 1.

Define specific heat capacity.

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 2. What is the specific heat of water? Is this relatively high or low compared to other substances? _______________________________________________________________________________ _______________________________________________________________________________ 3. Using the data table, which materials would be good insulators (high specific heat)? _______________________________________________________________________________ _______________________________________________________________________________ 4. Using the data table, which materials have a higher specific heat than water? _______________________________________________________________________________ _______________________________________________________________________________ 5. Using the data table, which material would make the best building material in a hot, dry region? Why? _______________________________________________________________________________ _______________________________________________________________________________ 6. Using the data table, which material would make the best material for a cooking pot to boil water in? Why? _______________________________________________________________________________ _______________________________________________________________________________ 7. Polystyrene is used in “to go” boxes from restaurants. Based on specific heat, why is this a common choice for restaurants? _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 8. Based on specific heat, why is porcelain a better choice for tea cup material over aluminum? _______________________________________________________________________________ _______________________________________________________________________________ _________________________________________________________________________ _______________________________________________________________________________

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Student Journal

PS7BC Thermal Energy

Reflections and Conclusions 1.

Identify the type of energy transfer (conduction, convection, or radiation) for each description below. Example of Heat Transfer

Conduction, Convection, or Radiation

Hot chocolate is stirred with a spoon and the spoon gets hot The Sun warms your skin on a cold day. Macaroni rises and falls in a pot of heated water. You burn your hand by touching a hot stove. Warming your feet in front of a fire. Hot air balloon rises. The air near the ceiling in a room is warmer than the air near the floor. The material in a lava lamp rises and falls. The sidewalk increases in temperature on a sunny day. The sidewalk burns your bare feet in the summer time.

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Student Journal Reflections and Conclusions, continued 2.

When particles of matter are in direct contact, conduction of thermal energy occurs in which states of matter?

________________________________________________________________________________________ ________________________________________________________________________________________ 3.

When particles of matter are in direct contact and movement occurs in the substance due to convection, thermal energy transfers in which states of matter?

________________________________________________________________________________________ ________________________________________________________________________________________ 4.

Which states of matter are required for energy transfer to occur when radiant energy is the source?

________________________________________________________________________________________ ________________________________________________________________________________________ 5.

Use your data from Part II to draw a conclusion. In thermal energy transfer by conduction, how does heat move between objects that are touching?

________________________________________________________________________________________ ________________________________________________________________________________________ 6.

Use your data from Part III to draw a conclusion. In thermal energy transfer by convection, what is the pattern of heat transfer through fluids?

Use your data from Part IV to draw a conclusion. In thermal energy transfer by radiation, how does distance from the thermal energy source affect the amount of thermal energy transfer occurring in a substance?

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STEMscopedia: THERMAL ENERGY PS7BC Reflect What kinds of things flow? Water flows in rivers. Air flows as winds blow across the planet. What about heat? Water and air are fluids, which means they are substances. It is easy to imagine how they flow. Heat is not a substance; it is a form of energy. However, heat does move from place to place. How do you think heat moves or “flows”? Thermal Energy, Heat, and Temperature What is thermal energy? All matter is made up of tiny particles, much too small to be seen. These particles are constantly moving, and motion is a form of energy. An object’s thermal energy equals the total energy of all its moving particles. What is heat? Heat is thermal energy that is being transferred from one place to another. Heat transfer happens when some of this energy moves from one object to another object. This occurs when there is a difference in temperature between the two objects. What is temperature? Temperature is the measure of the average energy of motion of an object’s particles. A thermometer measures the average energy of particle motion in an object. Consider the following example. On a hot summer day, suppose a glass of water and a lake have the same temperature. The average water particle in the lake and the average water particle in the glass have the same energy of motion. However, the lake has much greater thermal energy than the glass of water because it contains many more particles. In this case, heat would flow from the warm summer air into both the glass of water and the lake because heat flows from areas of greater energy into areas of less energy in an attempt to equalize temperature. Heat would not flow between the glass of water and the lake because their temperatures are already in equilibrium. Law of Conservation of Energy Energy can neither be created nor destroyed; it simply changes form. This is the law of conservation of energy. Most forms of energy are eventually transformed into thermal energy, which then flows away into nature. This is what we mean when we say that a system “loses” energy as heat. In most cases, we cannot capture and reuse this energy. For example, a fire gives off heat as it burns. Eventually, the fire burns itself out. Its energy has not been destroyed, even though we can no longer use it. It has simply been transformed into heat.

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STEMscopedia: THERMAL ENERGY Heat Transfer Thermal energy is transferred by three main processes: radiation, conduction, and convection. How does thermal energy move as heat from one object to another? Think of the different ways you experience heat. You feel heat as the Sun shines on you and as you sit by a fire. If you place a pot of water on a hot stove, you can see the water begin to boil. The stove can burn you if you touch it. Each of these processes involves the transfer of heat. How are they similar? How are they different?

Radiation Thermal energy can transfer by radiation. You don’t actually have to touch a hot frying pan to know it is hot. If you hold your hand a few inches from the pan, you can feel the heat. How is it possible to feel heat without touching a hot object? The answer is that hot objects emit radiation. Radiation is energy that travels as electromagnetic waves. You do not need to touch an electromagnetic wave to feel it. Examples of radiation include sunlight, campfires, microwaves, heat from our bodies, and light from light bulbs. Can you think of other examples? Like light, heat waves can travel through air. They can even move through empty space. Think about standing around a campfire or in front of a fire in a fireplace. Most of the heat you feel reaches you by radiation. If a large group of people is gathered around a campfire, only the people in the front row will feel the heat. If someone is standing in front of you, they will block the heat from reaching you. Conduction Thermal energy can be transferred by conduction. Imagine the tiny, constantly moving particles that make up an object. In a solid object, these particles vibrate back and forth while remaining locked in position. Now imagine placing a metal frying pan on a hot burner on a stovetop. The burner transfers heat to the pan, and the pan gets hot. The bottom of the pan gets hot before the pan’s handle. Why does this happen? Before the pan is placed on the burner, its particles are moving at the same average speed. The whole pan has the same temperature. The hot burner has a much higher temperature. In other words, the particles that make up the burner are moving at a greater average speed.

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STEMscopedia: THERMAL ENERGY When the pan is placed on the stove, the burner’s rapidly moving particles collide with the particles in the bottom of the pan. Some of the energy from the burner’s particles moves to the pan’s particles. As a result, the particles in the bottom of the pan begin to vibrate faster. These particles collide with nearby particles in the pan, which collide with other particles. Each collision passes energy from particles moving quickly to particles moving slowly. In this way, the energy spreads throughout the pan and finally reaches the handle. (Think of people doing the “wave” in the stands at a sporting event.) This process is called conduction. Conduction is the transfer of heat that happens when particles collide with each other and transfer energy. It occurs in solids, liquids, and gases, but it is most effective in solids because particles are close together and can easily make contact with one another. Convection Let’s talk more about the frying pan. Many kitchen stoves have hoods several feet above the burners. The purpose of the hood is to carry smoke and other fumes away from the stovetop. But why is the hood above the stove? Why isn’t it on the side? Similarly, why are chimneys above fireplaces? You never see a chimney beside or beneath a fireplace. The answer is that hot air rises. The third type of heat transfer is convection. During conduction, heat energy moves between particles that actually touch. During convection, however, the particles themselves move. This happens only in matter that flows, liquids and gases. The particles in solids are stuck in place and cannot move. Particles that move more quickly possess more thermal energy and are “hotter.” As those particles move into a new area, they increase the area’s thermal energy. This makes the area hotter as well.

As particles increase their speed, they also move farther apart. As particles in a group move apart, the whole group becomes less dense and thus lighter than the surrounding “colder” particles. As a result, the “hotter” particles rise. As particles rise, they gradually cool, lose energy, and sink. This creates a cycle of rising and sinking particles continuously participating in heat transfer. This circular motion is called a convection cycle.

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STEMscopedia: THERMAL ENERGY

Heat flows in a predictable pattern. Many people do not understand how heat energy is transferred. Have you ever heard someone say, “Quick, shut the door. Don’t let the cold air in!”? In reality, they should say, “Quick, shut the door. Don’t let the heat out!” Heat energy is transferred between objects with differences in temperature. Remember this important rule about heat flow: when objects of different temperatures are in contact, heat always moves from the warmer to the cooler object until their temperatures reach equilibrium. If you accidentally touch a hot burner, the heat moves from the burner to your hand because your hand is cooler. What happens if you touch a piece of ice? Heat moves from your hand, which is warmer, to the ice, which is cooler. In other words, your body loses heat, and that is why the ice feels cold. What Do You Know? A pot is placed on a gas flame, and the water inside the pot begins to boil. Heat moves in three different ways, as shown in the image below. Which part of the image shows radiation, conduction, and convection? Heat is carried away from the pot in all directions. This demonstrates ____________________. Warm water rises within the pot. This depicts ___________________. Heat moves from the flame to the bottom of the pot. This shows ___________.

What Do You Think? Specific Heat What is specific heat and how do we use it? Specific heat is a property of a substance. Each substance has a unique specific heat. The specific heat of a substance is defined as the amount of heat required to raise the temperature of one gram of the substance by one degree Celsius. For a particular substance, specific heat is a constant in the same way that boiling point and melting point are constants.

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STEMscopedia: THERMAL ENERGY The table below provides specific heat values for several common substances. Note that specific heat is measured in units of joules per gram per degree Celsius (J/g·°C). Substance Specific heat (J/g.oC)

Water 4.184

Wood 1.76

Glass 0.84

Copper 0.385

To think about the concept of specific heat and how it works, consider what it feels like to stand on a sandy beach on a hot summer day. When it is very hot, the sand becomes scorching—so hot that it hurts to walk barefoot across the beach to the water. Yet, when you step into the water, it feels cool. You might wonder why the sand is so hot and the water is so cool when both are exposed to the same conditions of air temperature and sunlight. How can the concept of specific heat solve this puzzle? (Here is a hint: The specific heat of water and the specific heat of sand are not the same. In the table above, you can use the specific heat of glass—which is made from sand—to approximate the specific heat of sand.) • • • • • • •

After inspecting the table and thinking through the concept of specific heat, answer the following questions: How do the two specific heat values of glass and water differ? Why does this explain your different experiences with hot sand and cool water? How does specific heat relate to conduction and insulation? What materials would you expect to have high specific heat values? What materials would you expect to have low specific heat values? Why? Based on specific heat, what materials would make good conductors of thermal energy? Why? Based on specific heat, what materials would make good insulators of thermal energy? Why? How does the specific heat of water play a role in keeping Earth’s temperature within a range that sustains life?

Connecting With Your Child Comparing Thermal Insulators and Conductors Different materials possess characteristics that may aid in thermal conduction or insulation. Perform an experiment with your child to help him or her better understand how insulators and conductors function.

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STEMscopedia: THERMAL ENERGY Materials: • 8 water bottles • wool sweater • cotton t-shirt • aluminum foil • bubble wrap • metal container • insulated container or water bottle • ice chest • thermometer For this experiment, you and your child will need eight identical plastic bottles filled with water. Place a thermometer in one bottle, and then put all the bottles in the refrigerator. Wait about an hour for all the bottles to cool to the refrigerator’s temperature; then, remove the bottles and record the temperature using the thermometer in one bottle. Next your child should follow this procedure: 1. Wrap four bottles in these materials (one per bottle): • a wool sweater • a cotton t-shirt • aluminum foil • bubble wrap 2. Pour the water from one bottle into a metal container. 3. Pour the water from one bottle into an insulated container. 4. Place one bottle in an ice chest. 5. Leave one bottle sitting at room temperature. After 30 minutes, record the temperature of the water in each container. List the materials from lowest temperature to highest temperature. Which material prevented the most heat loss? (This material is a good insulator or a poor conductor.) Which material prevented the least heat loss? (This material is a good conductor or a poor insulator.) Your child should note that aluminum foil was the best conductor. Explain that aluminum is a metal, and most metals are good conductors. Here are some questions to discuss with your child: 1. If you want to stay warm on a cold day, should you wear a wool sweater or a cotton shirt? Why? 2. What are some items made of insulating materials that prevent heat flow? 3. What are some items made of conducting materials that encourage heat flow? 4. If you place the bottles of water in the sunlight, the water will become warmer. Which process of heat transfer warms the water: conduction, convection, or radiation? Explain. 5. If you pour the water into a metal pot and heat it on a stove, the water will become warmer. Which process of heat transfer warms the water? Explain.

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PS7BC Thermal Energy

Reading Science Name:

Date:

Group:

What Does Calorimetry Tell Us? 1

What exactly is calorimetry? The process of calorimetry consists of experiments that calculate the heat flow between systems or within chemical reactions. The results of these experiments are used to determine the standard enthalpy (heat) of formation for a compound (represented by the symbol ΔHf or the enthalpy of a reaction (represented by the symbol ΔH). These are the values that you will see and use in thermochemical equations. All of these experiments must occur at constant pressure. Gases may have variable pressure within a container, so this is why calorimetry experiments take place in solution, where the pressure will remain constant. Why is this important? Remember, ΔH = q at constant pressure.

An ideal calorimeter would not have any heat exchange between the calorimeter and the surroundings, but this does not occur in the real world. No matter how insulated the calorimeter is, there will always be some sort of heat exchange between the calorimeter and the system or surroundings. This is why the heat flow of each calorimeter must first be calculated before using the calorimeter. This value lets you know the actual insulating power of the calorimeter, which can then be used in your calculations. Often it is expressed as a (cp) value, or the (m·c) of the calorimeter.

Several different kinds of calorimeters are used for different purposes. Often in chemistry, a specific type of calorimeter, known as a bomb calorimeter, is used to determine the energy contained within compounds. It is not called a bomb because it blows up. Bomb calorimeters are used to measure the energy given off by the sample that is burned within the apparatus. How does it work? Look at the graphic on this page. The small chamber that actually holds the sample is known as the “bomb.” It has a very tightly closing lid so that there is no exchange of air or heat between the bomb chamber and the surroundings. The mass of the sample of matter is carefully measured and is recorded as the value (m). Once the sample of matter is placed in the bomb, the bomb chamber is sealed, and pure oxygen gas is pumped in at a specific pressure.

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Reading Science 4

The entire bomb is then submerged in the bomb chamber as a small amount of pure water is added to the chamber. The water within the chamber removes the need to calculate the enthalpy of vaporization for the reaction, as this added water guarantees that any steam produced during the reaction will condense inside the chamber walls as water droplets. The water surrounding the bomb is kept at a constant temperature and is constantly stirred until the reaction occurs. This temperature is known as the initial temperature. This is why the specific heat of water is used in these calculations, represented by cp, with the value of 4.18 J/g•ºC. The heat capacity of the metal of the bomb is determined before the experiment and is known as the bomb factor.

Once the bomb is submerged in the water, the sample is ignited. The energy then released by the sample can be measured with great accuracy. The energy released by the combustion of the sample will change the temperature of the metal of the bomb, which in turn will change the temperature of the water surrounding the bomb. The temperature change of the water will be measured, and the change in temperature will be recorded as a ΔT value. The temperature change and the bomb factor readings can then be used to calculate the energy (q) given off by the sample. When you put it all together, q reaction = - (q water + q bomb). You can easily find the q water (mass • cp • ΔT of water), and oftentimes the cp of the bomb will be given.

Calorimeters are used for many reasons. One reason is to determine the calorie content of foods. Small samples of various food items are ignited in the bomb chamber, and the resulting energy released can be converted into the units of calories. Calorimeters can also be used to find enthalpy values for such things as the properties of specific geological materials, such as minerals. The calorimeter readings can help geologists determine the stability of samples and other materials. All of the ΔHf values that are used in thermochemical calculations are found through calorimetry as well.

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Reading Science 1.

Which process listed below would be used to measure the heat flow of a reaction? A.

Combustion reaction

Energy yield

Calorimetry

Thermochemical equations

The equation q (heat) = m (mass) • cp (specific heat) • ΔT (Tinitial - Tfinal) is used to calculate the heat transferred during a chemical reaction. Calorimetry reactions occur at constant pressure, which is important because ____________. A.

pure water is used

q = ΔH at constant pressure

the specific heat of the metal must be constant

the reaction will otherwise not occur

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Reading Science 3.

The picture below shows a typical bomb calorimeter.

Which component of the calorimeter assures that there is little to no heat exchange between the sample and the surroundings? A.

The bomb

The sample

The outer chamber

The water

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Reading Science 4.

The outer chamber of the bomb calorimeter is filled with a small amount of pure water. What is the purpose of the water within this chamber? A.

It removes the need to calculate the enthalpy of vaporization.

It keeps the reaction at constant pressure.

The ΔT of the water is used for calculations.

All of the above.

There are several uses for bomb calorimeter measurements in chemistry. Which of the following is not a use of a bomb calorimeter? A.

To find the number of atoms in a compound

To determine the calorie content of foods

To find enthalpy values for minerals

To find the standard enthalpy (heat) of formation for a compound

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Reading Science 6.

An unknown mineral is placed in a bomb calorimeter for analysis. The geologist wants to find out how much heat is released during the combustion of this unknown material. This will help her to understand the stability of this mineral under certain temperature conditions. She places a 1.2 g sample into the bomb calorimeter, which holds 800 g of water. The temperature within the calorimeter raises from 24.5°C to 32.6°C. The cp for the calorimeter is known at 830 J/g•°C. Find the q, in kJ, of the reaction for this sample of material.

Use the space provided above to show all of your work. A.

-120 kJ

- 33.89 kJ

200.4 kJ

53.4 kJ

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PS7BC Thermal Energy

Math Connections Name:

Date:

Group:

Heat and Calorimetry

Heat is a measure of the amount of thermal energy transferred during a reaction. A calorimeter is the instrument used for measuring the heat transfer (q). When it absorbs heat, the temperature increase of the substance in the instrument depends on its specific heat capacity (cp). The thermal energy required to change the temperature of a substance by a certain number of degrees can be calculated using the following equation: q = mcpΔT where q is the heat added or subtracted (joules), m is the mass of the substance (grams), cp is the specific heat capacity (joules/goC), and ΔT is the change in temperature (Tfinal – Tinitial). The specific heat capacity (cp) is the amount of energy needed to raise the temperature of one gram of a substance by one degree. 1.

Gold has a specific heat of 0.129 J/goC. How many joules of heat energy are required to raise the temperature of 16 grams of gold from 21oC to 86oC?

How much energy is required to warm a 1-kg block of ice from -15oC to 0oC? The specific heat of ice is 2.03 J/goC.

How much thermal energy is needed to bring 1.5-kg of water from 0oC to 16oC? The specific heat of water is 4.186 J/goC.

A 45-gram sample of solid lithium is heated up to 90oC and placed in cold mineral oil which drops the temperature of the lithium to 40oC. How many joules of energy did the lithium lose to the oil? The specific heat capacity for lithium is 3.58 J/goC.

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Math Connections Molar heat capacity (cm) is the amount of heat required to raise the temperature of 1 mol of a substance by 1oC. It is similar to the specific heat of a substance. The following formula can be used to calculate the heat needed to raise the temperature of a substance for any given number of moles: q = ncmΔT 5.

How much energy is required to warm a 3.5-mol aluminium from 15oC to 30oC? The molar heat capacity of aluminum is 24.2 J/(mol x oC).

What is the molar heat capacity of sodium chloride if it takes 1807.2 J to raise the temperature of 6 moles of NaCl by 6.0oC?

If it takes 1,680 J of mercury to heat an unknown amount from 16oC to 28oC, how many moles of mercury were heated? The molar capacity of mercury is 28 J/(mol x oC).

Twelve moles of copper were heated using 7,320 J. If the molar capacity of copper is 24.4 J/ (mol x oC) and the copper started at 31oC, what was the final temperature of the copper?

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Math Connections 9.

If 1315.4 J of heat is needed to heat a sample of iron from 6oC to 26oC, how many grams of iron was used in the sample? The molar heat capacity of iron is 25.1 J/(mol x oC).

10. What is the final temperature when 545 grams of water at 65oC loses 51244.98 J?

11. A 45.0 g piece of iron at 425oC is put into 535.0 grams of water at 15.0oC. What is the final temperature of the water and the iron when they are in equilibrium? The specific heat of iron is 0.451 J/goC and the specific heat of water is 4.186 J/goC.

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Writing Science Name:

Date:

LOOK

q = m · c · ΔT

THINK A calorimeter is used to experimentally measure thermal energy of a chemical reaction. The equation is used to calculate the heat transferred. Calorimetry is used by many types of scientists in the study of heat transfer. Knowing the quantity of the transfer of heat is essential in all areas including chemical manufacturing and even food production. The basic concept is the same for any calorimeter. A known amount of chemical is reacted, and the temperature change of the surroundings is measured. When placed into a formula including specific heat, the amount of heat transferred can be calculated. WRITE Give an explanation for each letter and symbol found in the equation q = m·c·ΔT. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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Writing Science Topic:

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Physical Science

PS8A

Motion of Objects

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PS8A Motion of Objects

Student Handout Name:

Date:

Balanced and Unbalanced Forces A force is simply a push or a pull that can change the motion of an object. Gravity is an example of a force that pulls objects toward each other. A box can be pushed across the floor with force, an umbrella is pushed open with force, and wind intensity can reach such force that it can push over trees and buildings. Forces always come in opposite pairs. For example, if a force is a push, then the opposing force will be a push in the opposite direction. If the forces on an object are EQUAL in size, then they are BALANCED and DO NOT cause a change in motion. If the forces on an object are NOT EQUAL in size, then they are UNBALANCED. Unbalanced forces cause motion. An object that is not moving starts moving when an unbalanced force is applied. An object that is moving changes its speed or direction when an unbalanced force is applied. The size of the arrows shown on the examples below show the amount of force applied. Notice that the forces are always shown as pairs. The direction of the arrow shows the direction of the acting force. Remember: Balanced forces = no motion change. Unbalanced forces = motion change.

Unbalanced: causes motion in direction of larger force

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Balanced: no change of motion

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PS8A Motion of Objects

Student Handout Directions: Use the graphic to help you determine if the object is balanced or unbalanced. Answer the questions for each example. Are the forces balanced or unbalanced? ________________ Will the ball change speed or direction when acted upon by the forces? ____________________________________ If so, draw in an arrow to show the resulting change of motion. Are the forces balanced or unbalanced? ________________ Will the rocket change speed or direction when acted upon by the forces? _________________________________ If so, draw in an arrow to show the resulting change of motion. Are the forces balanced or unbalanced? ________________ Will the apple change speed or direction when acted upon by the forces? ____________________________________ If so, draw in an arrow to show the resulting change of motion.

You draw in the force arrows. The size and direction of your force arrows will determine if any resulting change of motion will occur to the box. Label “no motion” or show the resulting box motion with an arrow.

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PS8A Motion of Objects

Student Journal Name:

Date:

Group:

Background 1.

What is speed?

_______________________________________________________________________________ _______________________________________________________________________________ 2.

Show the formula and calculate the speed of a car that traveled 100 km in 2 hrs.

____________________________________________________________________________ 3.

What is velocity?

_______________________________________________________________________________ _______________________________________________________________________________ 4.

Show the formula and calculate the velocity of a runner that runs south 10 km in 1 hr.

____________________________________________________________________________ 5.

What is acceleration?

_______________________________________________________________________________ _______________________________________________________________________________ Read the description of Juan’s motion during a race. When the race started, Juan’s speed increased until he was running at a constant speed of 6 m/s. After 17 s, Juan’s velocity changed to 5 m/s to the northwest and remained constant for 20 s. Finally, Juan’s velocity changed to 7 m/s north, and he crossed the finish line. Juan then walked back to the starting line at a slow constant speed of 1 m/s. 6.

What are the examples of speed from the description of Juan’s race?

_______________________________________________________________________________ _______________________________________________________________________________ 7.

What are the examples of velocity from the description of Juan’s race?

_______________________________________________________________________________ _______________________________________________________________________________ 8.

What are the examples of acceleration from the description of Juan’s race?

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PS8A Motion of Objects

Student Journal Part I: Plan Your Investigation 1.

My question of inquiry:

_______________________________________________________________________________ _______________________________________________________________________________ 2.

What is the setting and scale of this investigation?

_______________________________________________________________________________ _______________________________________________________________________________ 3.

What is the time frame of this investigation?

_______________________________________________________________________________ _______________________________________________________________________________ 4.

What will you observe in this investigation?

_______________________________________________________________________________ _______________________________________________________________________________ 5.

Identify what tools, equipment, and technology you need to complete the investigation and why. Use additional paper as necessary.

List all the safety precautions that must be taken.

Outline the steps of your procedure. Use additional paper as necessary.

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PS8A Motion of Objects

Student Journal Part II: Implement Your Investigation Collect, Record, and Organize Data

Record distance data for each walk in the tables below. After you complete the four walks, you will calculate the speed and velocity for each interval of the walk and add to the data table. Walk 1 Distance

Time

Speed for this Interval 0 m/s

Velocity for this interval 0 m/s

Walk 2 Distance

Time

10 s

15 s

20 s

Walk 3 Distance

Time

Speed for this Interval 0 m/s

Velocity for this interval 0 m/s

Distance

Time

0s 5s

10 s

15 s

20 s

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Velocity for this interval 0 m/s

Speed for this Interval 0 m/s

Velocity for this interval 0 m/s

Walk 4

Speed for this Interval 0 m/s

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Student Journal Part II: Implement Your Investigation, continued Analyze Data Use your data to create distance versus time graphs and speed versus time graphs. Walk 1 Speed v. Time

Speed

Distance (m)

Walk 1 Distance v. Time

Time (s)

Legend

Legend Walk 2 Speed v. Time

Speed

Distance (m)

Walk 2 Distance v. Time

Time (s) Legend

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Time (s) Legend

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PS8A Motion of Objects

Student Journal Part II: Implement Your Investigation, continued Analyze Data

Walk 3 Speed v. Time

Speed

Distance (m)

Walk 3 Distance v. Time

Time (s)

Legend

Legend Walk 4 Speed v. Time

Speed

Distance (m)

Walk 4 Distance v. Time

Time (s) Legend

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Time (s) Legend

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Student Journal Part II: Implement Your Investigation, continued Analyze Data 1.

Describe the speed, velocity, and acceleration of the walker in Walk 1.

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 2. Compare the distance versus time graph and the speed versus time graph for Walk 1. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 3. Describe the speed, velocity, and acceleration of the walker in Walk 2. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 4. Compare the distance versus time graph and the speed versus time graph for Walk 2. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 5. Describe the speed, velocity, and acceleration of the walker in Walk 3. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 6. Compare the distance versus time graph and the speed versus time graph for Walk 3. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 7. Describe the speed, velocity, and acceleration of the walker in Walk 4. _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ 8. Compare the distance versus time graph and the speed versus time graph for Walk 4. _______________________________________________________________________________ _______________________________________________________________________________

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Student Journal

PS8A Motion of Objects

Part II: Implement Your Investigation, continued Analyze Data 9.

Which graph(s) shows movement at the highest rate of speed? How do the graphs show you this?

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PS8A Motion of Objects

Student Journal Reflections and Conclusions 1.

Define the following terms in your own words. a. speed _______________________________________________________________ b. velocity ______________________________________________________________ c. acceleration __________________________________________________________

How is speed shown on a distance versus time graph?

_______________________________________________________________________________ _______________________________________________________________________________ 3.

How can you determine if an object is accelerating by looking at a distance versus time graph?

_______________________________________________________________________________ _______________________________________________________________________________ 4.

How can you determine if an object is accelerating by looking at a speed versus time graph?

Which graph(s) demonstrate(s) an object that is traveling at a constant speed for the entire period of time?

_______________________________________________________________________________ 6.

Which graph(s) demonstrate(s) an object changing velocity (i.e., changing speed or direction)?

_______________________________________________________________________________ 7.

Which graph(s) demonstrate(s) an object stopping for a period of time?

_____________________________________ 8.

Which graph(s) demonstrate(s) an object that is accelerating for the entire period of time?

_______________________________________________________________________________ 302

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STEMscopedia: MOTION OF OBJECTS PS8A Reflect Have you noticed that when describing motion, people tend to define it based on what they can see? Can objects be in motion without anyone actually seeing the object move? If we can quantify the motion, how would we represent the information? How would you represent when the motion of an object stops or changes? Motion is not just moving. So what is motion and how can we tell if something moved? When asking a classroom full of students what motion is, you usually get the answer of objects are in motion when you can see the object moving. Can you always see motion? We know that subatomic particles move, but can you always see it? So what is motion? Motion is the changing of position or place based on a reference point. How many times have you been in a long car ride with your family? When your mind wanders, you start fixating on staring at trees or telephone poles as they pass by your car. All those trees and telephone poles were your reference points. Your car passed each of them, showing that motion is occurring. So did the tree or telephone pole move, or was your car in motion? Hopefully, your car was in motion, which also means that you are in motion with the car. You do not have to do any calculations because the car’s speedometer does the work for you. If your car is going 60 miles per hour, then both you and the car are traveling at that speed. It means that your car will travel approximately 60 miles in one hour. Motion of objects can be quantified by various mathematical formulas. If you did have to calculate the speed, you would need to know a few things. So what is speed and how can it be calculated? Speed is defined as the distance an object travels in a certain amount of time. Basically, it quantifies how fast an object moves. The formula is speed = distance ÷ time. You can easily remember this formula by stating how fast a car moves. When stating how fast a car moves, we state that a car is moving at 60 miles per hour. Miles is the distance, and hour is the time. So distance (miles) divided by (per) time (hour). To calculate the speed of an object, you must determine the distance the object traveled or how much ground the object has covered and how long it took for the object to travel from point A to point B. If you ever competed in track events, you know they have lines marked for the start and the finish of the race. They time you to determine your speed. Fill in the information into the formula, divide and make sure to include a unit of measurement. Common units of measurement for speed include kilometers per hour, miles per hour, and meters per second.

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STEMscopedia: MOTION OF OBJECTS When we discuss speed, we also need to discuss velocity. These two words are not interchangeable. Even though they both calculate speed, they have a slight difference. Velocity is a very specific type of speed because it involves direction. Velocity is speed plus the direction. So when we discuss the speed of a hurricane, we state that it is traveling at 90 miles per hour. For us to discuss the velocity of the storm, we would need to include a specific direction. So a hurricane traveling at 90 miles per hour moving in a northeast direction, changes it from speed to velocity. You can determine the velocity of an object based on its displacement. Displacement means that an object moved from one place to another or how far out of place the object has become. When you place an irregular object in a graduated cylinder, you can find the volume of the object due to the displacement of water, since two objects cannot occupy the same place at the same time. So when an object moves, you can calculate that motion into velocity by determining the displacement of the object, the time it took to get to that point and the direction in which it traveled. You can change the velocity of an object based on changing the speed and/or the direction of the object. By changing the speed and/ or direction of an object, you have changed the acceleration of the object. If the speed or velocity increases, it is called acceleration. If the speed or velocity decreases, it is called deceleration. Acceleration can also be changed based on the change in direction of the object. Consider the following scenario. You are rushing to pack up your items and dash out of the classroom in a hurry, so you are accelerating your body by increasing your speed. Once you arrive at your next class, you slow down, or decelerate, when you remember that you left your calculator in your last class. You rush out to retrieve your calculator and change your velocity due to your change in direction. See, you cannot escape lessons in science!

Try Now Now that we have some background information, let’s see if you can determine which example clearly shows speed and which shows velocity. What Do You Know? For each example sentence, determine if the example is demonstrating speed or velocity. Write your answer in the space provided. __________________ 1. A race car moves at 200 miles per hour. __________________ 2. The hurricane is traveling at 98 miles per hour in a northerly direction. __________________ 3. A man ran a race at 11 meters per second. __________________ 4. A cheetah runs 120 kilometers per hour going east toward the gazelle.

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STEMscopedia: MOTION OF OBJECTS Look Out Don’t let the motion graphs confuse you. Imagine this scenario. You decide you are going to get some exercise today. You get on your bike and go as fast as you can for as long as you can. As you ride, you get faster and faster by the minute. After about 10 minutes, you realize that you need a break, so you stop for five minutes to get a water from the local convenience store. You get back on your bike but realize that you were kidding yourself when you started this morning. So you decide to ride at a steady pace long enough to make it home. If we graphed your experience today, what would your motion graph look like? Look at the two graphs below and decide which one best follows this scenario.

Did you choose B? If you did, great! That means you understand how a motion graph works. Check out the following graph:

Since you started off with great energy and continued to increase your acceleration, the line would curve to show the acceleration in speed. When you stopped, time continued while your distance flatlined. It flatlined because you did not change your position in relation to the distance from point A (your home, which was the starting point). When you decided to go home, you rode at a constant speed so the line straightened out. Since you were riding back to the original starting point, the line also heads back down to the starting line.

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STEMscopedia: MOTION OF OBJECTS Connecting With Your Child To make the concepts more concrete and more interesting, you and your child can create a “minute to win it” environment. Based on the items you have at home, create ministations to compete with your child in a race to complete various tasks. Here are some suggestions, based on common household items: Materials • 20 plastic cups • Timing device (watch or phone) • Box of paper clips • Slice of bread with honey (or peanut butter or molasses) • 2 balloons Procedure 1. Set up six plastic cups at one station with the objective of stacking all six cups to make a pyramid shape. You will need to stack all six and take them down as fast as you can. Do this for one minute. Count how many times you built the completed pyramid design. 2. Set up a slice of bread on a table. Spread honey, peanut butter, or molasses on the slice of bread. From a distance of five feet, toss the paper clips onto the bread. Count the number of paper clips that stick to the bread in one minute. 3. Set up all 20 plastic cups upside down on a table. Blow up a balloon and when time starts, try to knock as many cups off the table using only the air in the balloon. Count how many cups you knocked off the table in one minute. After you have completed the tasks for each station, try the task one more time to see if you change your acceleration of the tasks. Make sure to calculate the speed of each task based on the unit of item per second, which means you will need to convert. Bonus Challenge: If you have more time, take a walk, jog, or run around your neighborhood and track your speed. When you get home, graph the motion of your journey.

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PS8A Motion of Objects

Reading Science Name:

Date:

Group:

Rutherford’s Scattering Experiment 1

Motion of an object can be determined by its speed, velocity, and/or acceleration. The distance an object travels over a certain period of time is its speed. An object’s speed and the specific direction it is traveling are its velocity. A change in an object’s velocity over a specific period of time is called acceleration. In order to measure velocity, you must know the speed and direction of a given object. Imagine riding in the car with your family as you take a trip to the mall. As you head down the street, your mother applies pressure to the gas pedal to move the car forward. The car, which was previously moving at 25 miles per hour, is now proceeding ahead at 45 miles per hour. Pushing the gas pedal causes the car to accelerate, or speed up. Because the constant rate of speed or the velocity of the car increases, your family will get to your destination much faster. In this case, the velocity and the acceleration of the car are in the same direction.

Velocity can be constant, or it can change. Once your family reaches the main highway, your car is stuck in weekend traffic. Because of this, your mother now applies pressure to the brake pedal, causing the car to slow down, or decelerate. The car slows back down from 45 miles per hour to 25 miles per hour. In this case, the velocity of the car and its acceleration are in opposite directions. When you accelerate or decelerate, you change your velocity by a specific amount over a specific amount of time.

For motion to be described accurately, it needs to be described relative to a point of reference. A point of reference is just an object or position near the object in motion. During your trip to the mall, there are several ways to describe your motion. Assume that you are sitting in the car and it is moving at a speed of 25 miles per hour. Here, the ground is your point of reference. Both you and the car are moving 25 miles per hour relative to the ground. If the car is the point of reference, then you are not moving relative to the car. If you pass a car that is driving 20 miles per hour, then you are moving 5 miles per hour relative to the other car. Three different points of reference result in three different descriptions of your motion. For this reason, it is important to indicate your point of reference when measuring velocity. Most often, speed is determined with respect to the ground. However, there are instances when the speed or velocity may be determined with respect to an object or an observer.

Remember, you need to know two things in order to truly describe how fast an object is going. You need to know its velocity and the point of reference. How else can the officer tell if your mother is speeding?

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PS8A Motion of Objects

Reading Science 1.

Which of the following could be a definition of acceleration? A.

A change in an object’s speed

An object at rest

A change in an object’s direction

Both A and C

In which of the following three situations is the object accelerating? 1.

A trash truck takes off from the curb.

A book rests on a shelf.

An airplane banks to circle around the airport.

1 and 3

1, 2, and 3

When a police officer is trying to decide if a driver is speeding, what is his point of reference? A.

The ground

His car

The speed limit

All of the above

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PS8A Motion of Objects

Reading Science 4.

Which words help you to determine the meaning of the word decelerate in the third paragraph? A.

Velocity can be constant, or it can change

Applies pressure to the brake pedal

The car will slow down

Stuck in weekend traffic

A bowling ball moves 18 meters every 2 seconds down the lane at a bowling alley. What is the speed of the bowling ball? A.

2 meters per second

9 meters per second

18 meters per second

36 meters per second

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PS8A Motion of Objects

Math Connections Name:

Date:

Group:

Part I: Speed and Velocity

Speed is a scalar quantity that refers to how fast an object is moving. Velocity is a vector quantity that refers to the speed of an object in a specific direction. Essentially, velocity is speed in a specific direction. Average speed is often calculated using the following formula: Average speed (s) = total distance traveled (d) / total time of travel (t) Average velocity is often calculated using the following formula: Average velocity (v) = displacement (meters) / time (sec) 1.

Based on the units given for displacement and time, what will the units for velocity be?

During summer vacation, Juan traveled a total distance of 400 miles. His trip took 8 hours. What was the average speed during his trip?

An alert driver can apply the brakes fully in about 0.5 seconds. How far would the car travel if it were moving at a rate of 29.06 m/sec?

In 2013, the average time men in the United States could run a marathon was about 4 hours and 16 minutes. If a marathon is 26.2 miles, what was the average speed?

In the same year, the average finishing time for U.S. women was 4 hours and 41 minutes. What was the average female speed in miles per hour?

Part II: Acceleration

Acceleration is the rate at which an object changes its velocity. Acceleration is a vector quantity, meaning that it has a direction. The average acceleration of an object is its change in velocity over a given amount of time. Average acceleration can be calculated using the following formula: Average acceleration = Change in velocity (Δv) / time (t) 1.

If the velocity of a moving car increases from 9 m/sec to 25 m/sec in the span of 5 sec, what is the average acceleration during this time period?

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PS8A Motion of Objects

Math Connections 2.

Usain Bolt, the Olympian from Jamaica, is the fastest human ever recorded. Determine his average rate of acceleration if he achieved a speed of 10.4 m/s in 9.58 sec. (Think about what a sprinter’s initial speed is.)

Use the following information to answer questions 3–5. The following data were taken from a manufacturer’s test for a car’s ability to accelerate and brake. Plot the following set of data on the graph provided. Time (s)

Speed (m/s)

Time (s)

Speed (m/s)

Write a short description about what the graph shows.

What was the average acceleration during the time between 24 sec and 40 sec?

What was the average acceleration during the time between 40 sec and 46 sec?

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PS8A Motion of Objects

Writing Science Name:

Date:

LOOK

THINK Think about the motion experienced on a roller coaster ride. WRITE Explain the difference between speed, velocity, and acceleration. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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PS8A Motion of Objects

Writing Science Topic:

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Physical Science

PS8BC

Newton’s Three Laws and Force of Gravity

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PS8BC Newtons Three Laws and Force of Gravity

Student Handout Name:

Date:

Watch the video clip of “pool trick shots.” Then discuss and answer the questions below. 1.

When a ball was struck, how did it move?

If two balls collided, did they continue moving in the same direction?

If the cue was moved slowly as it struck the ball, what would happen to the speed of the ball?

When a ball struck to the side rail of the pool table, it would bounce back and continue moving. What is another example of this behavior in everyday life?

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PS8BC Newton’s Three Laws and Force of Gravity

Student Journal Name:

Date:

Group:

Part I: First Jar Race 1.

How far did your jar with sand travel?

_______________________________________________________________________________ 2.

How far did your jar with metal parts travel?

_______________________________________________________________________________ 3.

How far did your empty jar travel?

_______________________________________________________________________________

Part II: Second Jar Race 1.

How far did the jar on the steeper ramp travel?

_______________________________________________________________________________ 2.

How far did the jar on the more shallow ramp travel?

_______________________________________________________________________________

Part III: Jar Demolition Derby 1.

Which jar was moving faster at the moment of collision?

_______________________________________________________________________________ 2.

Which jar rebounded furthest after collision?

_______________________________________________________________________________ 3.

Which jar is heaviest?

_______________________________________________________________________________

Part IV: Jar Drop 1.

Which jar is heaviest?

_______________________________________________________________________________ 2.

Which jar do you predict will fall fastest?

_______________________________________________________________________________ 3.

Did the jars land at the same time? If not, which one landed first?

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PS8BC Newton’s Three Laws and Force of Gravity

Student Journal Part V: Newton’s Laws 1.

An object in motion remains in motion.

An object’s acceleration is related to its force.

For every action there is an equal but opposite reaction.

Gravity pulls on all objects equally regardless of their mass. Experiment

Newton’s Law

Evidence

First Jar Race Second Jar Race Demolition Derby Drop

Reflection Questions 1.

What force causes the jars to roll down the ramp?

What force causes the jars to slow down and stop rolling once they have left the ramp?

Why did the jars travel faster on the steeper ramp than the more shallow ramp?

Newton’s second law states that as the mass of an object increases, a force will cause less and less acceleration. Design an experiment to show this using your jars, ramps, and sand.

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STEMscopedia: NEWTONS’ THREE LAWS

AND FORCE OF GRAVITY

Reflect

PS8BC

If you were to drop a book and a paper clip at the same time, which object do you predict would hit the ground first? Why do you think your prediction is correct? Now try it yourself. Was your prediction correct? Gravity Gravitational force is key to our existence. If gravity did not exist, Earth would not revolve around the Sun; the Moon would not revolve around Earth; and most importantly, you would not be walking on Earth, but rather floating around in space somewhere! The larger the mass, the more gravitational force an object has. For example, the Sun is the largest object in our solar system; therefore, all planets revolve around the Sun due to the Sun’s gravitational force. Mass only affects gravitational force if an object is extremely large, such as the mass of another planet. On Earth, we have objects with different masses, but they are not extreme differences; On Earth, the gravitational force on all objects found on Earth is the same. All objects that are dropped on Earth fall at a rate of 9.8 m/ s2. All objects dropped on Earth accelerate at the same rate. If you were to drop a bowling ball and a marble from the top of the Empire State Building, the two objects will hit the ground at the exact time.

Look Out Gravity is a force that acts on all objects on Earth. Every object on Earth falls at 9.8 m/s2. The exception to this is if you were to drop a feather or a piece of paper, it may fall slower due to the air resistance force that acts on the object. In the 1960s astronauts walking on the Moon decided to test the gravitational forces on the Moon. The Moon does not have an atmosphere; therefore, there is not any air resistance present. The astronaut dropped a feather and a hammer at the same time. The feather and hammer hit the Moon at the exact same time, proving that without air resistance all objects have identical gravitational forces acting on them.

Reflect Does anything happen without a cause? Many people would say yes because that often seems to be our experience. A cup near the edge of a table suddenly crashes to the ﬂoor. An apple falls from a tree on a clear, windless day. An enormous bank of snow breaks loose from a mountainside and comes roaring down the slope as an avalanche, leveling trees that stand in its path. These events do not “just happen.” Any change in motion is the result of a force. The forces that cause change are not always obvious, but they are always present. Relationships between force and change in motion follow three precise laws. What are these laws?

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STEMscopedia: NEWTONS’ THREE LAWS

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How do they help us understand force and motion? Force and Motion State of motion is an important concept. These are the four states we will consider, which are broken into two categories: Constant 1. Motionless 2. Moving at constant speed in a straight line Changing 3. Increasing or decreasing speed 4. Changing direction at a constant speed Changing an object’s state of motion from one category to another requires a change in the force or forces acting on the object. There are two types of forces, balanced and unbalanced. When all the forces acting on an object cancel each other out, they are balanced. In other words, the net force is zero. This is the case for the two categories of constant motion, motionless, and moving at a constant speed in a straight line. If the forces acting on an object do not cancel, the net force is not zero. These are referred to as unbalanced forces. Unbalanced forces cause motion to change from one state to another. Consider the avalanche. Before the avalanche, the force of gravity acting on the snow was equal to the force of friction between snowﬂakes (and any other force acting in opposition to gravity). The forces were balanced and the state of motion was motionless. Some event, such as melting, reduced the frictional force so that it was less than the gravitational force. The net force became unbalanced and the snow began to move.

An unbalanced force set this avalanche in motion.

Newton’s First Law It was mentioned earlier in the lesson that three basic laws explain the relationships between force and motion. These are Newton’s three laws of motion. Newton’s ﬁrst law, the law of inertia, addresses the case of objects in a constant state of motion. The objects are either motionless or moving at a constant speed in a straight line. The law states that an object at rest stays at rest, and an object in motion stays in motion until unbalanced forces act upon it. Inertia refers to an object’s resistance to a change in motion. Inertia is directly related to mass. The more mass an object has, the more inertia it has and the more it resists a change in motion. Think about trying to move objects that have different masses, such as a lamp and a sofa. Obviously the lamp is much easier to move.

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STEMscopedia: NEWTONS’ THREE LAWS

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It is not as obvious that an object will continue to move in a straight line at a constant speed if the forces on it are balanced. Everyday experiences seem to contradict the law of inertia. Every moving thing we see slows down if we don’t make some effort to keep it moving. Things slow down naturally because unbalanced forces of friction and air resistance always act on them. If you kick a soccer ball across a ﬁeld, for example, the ball slows down because friction between the ball and the grass is an unbalanced force. If there were no friction, the ball would continue to roll without slowing down. For things that do travel at constant speed, some force acting on the object exactly balances the forces of friction and air resistance, resulting in a net force of zero. A The need for seatbelts is retrain, for example, can travel at a constant speed because the force of lated to inertia and the ﬁrst the engine acts on it.. law of motion.

What Do You Think? When you are riding in a car and it comes to a sudden stop, why do you lurch forward? Has the net force on you changed? What is the tendency of objects moving at a constant speed in a straight line? The answer is related to the need for seatbelts and infant car seats. Newton’s Second Law Newton’s second law of motion states that when an unbalanced force acts on an object, the object accelerates at a rate equal to the net force on the object divided by the object’s mass. This law is expressed by the equation: a = F/m. In this equation, the acceleration (a) is expressed in meters per second per second, which are meters per second squared (m/s2). The net force (F) is in newtons (N), and the mass (m) is in kilograms (kg.) The equation is more often seen in the form: F = ma. As long as a net force acts on an object, the object will continue to accelerate. In many everyday events, an unbalanced force will only act brieﬂy, as in the case of hitting, kicking, or throwing a ball. One familiar exception is the force of gravity acting on a falling object. Falling objects continue to accelerate until the force of air resistance equals the force of gravity. Suppose you wanted to design a car that could accelerate from 0 to 60 mph (miles per hour) in 10 seconds. How much force would the engine have to exert? The mass of a car is about 1,500 kg, and 60 mph ≈ 27 m/s. Recall that acceleration is the change in velocity divided by the change in time. Acceleration = change in velocity/time = (27 m/s – 0 m/s)/10 s = (27 m/s)/10 s = 2.7 m/s2

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STEMscopedia: NEWTONS’ THREE LAWS

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Since you know the acceleration, you can use the second law of motion to calculate the force required to cause this acceleration. F = ma = (1,500 kg)(2.7 m/s2 ) = 4,050 m·kg/s2 = 4,050 N

Look Out Slowing down is also acceleration. It is often referred to as deceleration; however, in scientific terms, it is called negative acceleration. When something slows down, it is because an unbalanced force is acting in a direction opposite of the object’s motion. In most cases, this unbalanced force is the force of friction. Newton’s Third Law Newton’s third law of motion is often stated, “For every action force, there is an equal and opposite reaction force.” You may think, “Wait, that does not make sense!” But it is true. All forces occur in pairs, and no force exists alone. You push on a door to open it, and the door pushes back with an equal force in the opposite direction. After all, you can feel the door, can’t you? As you walk, you push on the pavement with the sole of your shoe. The pavement pushes in the opposite direction, sending you forward. It may seem more logical if you think of force pairs as an interaction between objects. An object always interacts with another object. Think about two ice skaters facing each other. If one skater pushes on the other’s hands, both skaters move backward. The first skater’s action force caused a reaction force from the other skater, even though the second skater did not try to push back. Scientists in the Spotlight: Isaac Newton Sir Isaac Newton, an Englishman who lived from 1642 to 1727, made an amazing number of important contributions to science. In addition to developing his three laws of motion, Newton developed the law of universal gravitation. This law explains how gravitational force varies with the masses of two objects and the distance between them. The greater the mass of the objects, the greater the gravitational force is between them. The greater the distance between two objects, the weaker the gravitational force between them. Newton also did important work in the fields of optics, astronomy, and chemistry. He also wrote extensively on religious topics. He was influential in establishing the main ideas of the scientific method, and he argued that the laws of science apply to objects in space in the same way they Sir Isaac Newton made apply on Earth. His ideas were slow to be accepted by some scientists. important contributions to The idea that a force, like gravity, could act at a distance without our understanding of forces contact between objects sounded too mysterious and magical for many and motion. scientists to believe. 324

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STEMscopedia: NEWTONS’ THREE LAWS

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What do you know? Everyday objects illustrate Newton’s three laws of motion in countless ways. The chart below lists some examples of the laws in action. For each example, write which law it best illustrates, and explain your answer. Examples of Laws of Motion Which Law is Best Illustrated? Why? Maya hits a curb while riding her bike. The bike stops moving, but Maya is thrown into the air for a split second. A bird flaps its wings, using them to push air downward. Air pushes upward on the bird, allowing the bird to fly. Peter pushes on two boxes with equal force. The first box is filled with books and the second box is filled with balloons. The second box accelerates at a greater rate than the first box.

Connecting With Your Child Force and Motion in Olympic Events To help your child learn more about Newton’s three laws of motion, begin with a review of each law: •

The first law is the law of inertia. This law states that an object at rest tends to stay at rest, and an object in motion tends to stay in motion at constant speed in a straight line. That is, the state of motion of an object does not change unless it is acted upon by an unbalanced force. Therefore, if the net force is 0, nothing happens.

•

The second law of motion states that the relationship between force (F), mass (m), and acceleration (a) is F = ma. This equation can also be written as a = F/m. More force makes things accelerate at a greater rate, and more mass slows the rate of acceleration.

•

The third law of motion is the law of action-reaction. For every action force, there is an equal and opposite reaction force. Forces always occur in pairs––never alone. When you push on something, it pushes back with an equal amount of force in the opposite direction.

Now you are ready to observe the laws in action! A good place to observe forces at work is at a track meet or gymnastics competition. If you cannot visit one of these, try to watch videos of the Olympics or ﬁnd pictures of the equipment involved. Alternatively, you and your child could visit a school that competes in track or gymnastics.

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STEMscopedia: NEWTONS’ THREE LAWS

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Study several events and observe how the three laws of motion describe the forces and motion involved. Here are some examples of events to consider: • • • •

Shot put: What are the acting forces? What is the effect of the shot put’s mass? Discus: In which ways does the discus change its state of motion? Javelin: Why does it go farther than the shot put? What are the forces involved? Foot races: When are the racers accelerating?

For all of the events, discuss the effects of force and mass on acceleration. Identify action and reaction forces, and try to ﬁnd the causes of positive and negative acceleration. Here are some questions to discuss with students: 1. A girl throws a ball to a dog, and the dog catches it in its mouth. At what point does the force exerted by the girl’s hand stop affecting the motion of the ball? 2. One child is pushing two other children on a sled. One child gets off the sled and helps to push. Explain two ways this change affects the motion of the sled in terms of the second law of motion. 3. Identify the action force and the reaction force acting on a person sitting in a chair.

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PS8BC Newton’s Three Laws and Force of Gravity

Reading Science Name:

Date:

Group:

Newton’s Laws and Roller Coasters 1

In 1687, Sir Isaac Newton published the Principia. This book contained his three laws of motion, which changed mechanics forever. These three laws became the foundation of classical mechanics. Newton’s three laws of motion have been proven over and over again in the last three centuries. They are the basis of many of our modern inventions.

The roller coaster, a modern invention that uses the laws of motion to thrilling ends, is one of the best uses of Newton’s laws of motion. Roller coasters, with their twists, turns, and loops, seem to defy everything we know about how people and objects move. Roller coaster designers, however, simply use Newton’s laws to push people past their usual limits. Early roller coasters, like Coney Island’s Flip Flap, even caused whiplash and broken necks due to abrupt, high g-forces.

Newton’s first law is the law of inertia. This states that an object at rest stays at rest, or an object in motion stays in motion until unbalanced forces act upon it. Most roller coasters run by the law of inertia. Since an object at rest stays at rest, all roller coasters have to be pushed or pulled to get started. Most are pulled up a large hill called a lift hill. The first hill is usually the biggest hill. As the cars go uphill, they store potential energy. At the top, the cars have the largest amount of gravitational potential energy. They are about to be put into motion. Roller coaster cars will gain enough energy from the lift hill to be powered through the rest of the ride. Once put into motion, they will not stop until the brakes are applied at the end of the ride.

Newton’s second law is the law of force and acceleration. This law states that the acceleration of an object depends on the object’s mass and the magnitude of the force acting upon it (F = ma). You feel this second law when you start going down the hills. The coaster cars and your body have mass. The gravity provides acceleration, which causes force. The rider feels the force as it moves the cars along the coaster track. The track directs the force and the cars. The mass of your body and the coaster cars is constant. The amount of force changes due to changes in acceleration. The changes in acceleration are due mostly to friction. The thrill of acceleration on a roller coaster comes from Newton’s second law.

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PS8BC Newton’s Three Laws and Force of Gravity

Reading Science 5

Newton’s third law of action-reaction states that for every action, there is an equal and opposite reaction. This means that as you push down on the seat, the seat pushes back at you. This law really comes into play with newer roller coasters that expose riders to high g-forces. A “g-force” relates an acceleration on a body to the acceleration due to gravity. What happens in a two g-force turn? Your body will experience an acceleration twice as strong as the pull of gravity. Older roller coasters did not expose riders to very many g-forces. Newer roller coasters, however, can expose riders to very high g-forces. At least one death has been caused by a rider’s body reacting to the g-forces on a roller coaster.

G-forces, like all forces, are not just acting on the things we can see. They are also acting on our blood and our blood vessels. Just as they push your body into the seat, they push your blood back away from your brain and toward your feet. G-forces can detach your retina and even make you pass out. As we use the laws of physics to create more exciting roller coasters, it will be important to keep in mind the limits of our human bodies.

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PS8BC Newton’s Three Laws and Force of Gravity

Reading Science 1.

What kind of statement is, “Roller coasters are one of the best uses of Newton’s laws of motion”? A.

An opinion

A fact

The truth

A question

What conclusion can you make about g-forces based on the information in the last paragraph? A.

G-forces help your heart to beat properly.

G-forces can be harmful to your health.

G-forces make the blood in your body rush to your head.

G-forces lift you out of the roller coaster seat.

Newton’s law of inertia explains why roller coasters _____________. A.

start with a big hill

cause damage to the human body

need constant pulling to stay moving

are fun

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PS8BC Newton’s Three Laws and Force of Gravity

Reading Science 4.

Newton’s second law explains why roller coasters _____________. A.

start with a big hill

have seat belts

do not have brakes

change speeds

Which of Newton’s laws states that for every reaction, there is an equal and opposite reaction? A.

Newton’s first law Newton’s first law

Newton’s second law

Newton’s third law

None of the above

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PS8BC Newton’s Three Laws and Force of Gravity

Math Connections Name:

Date:

Group:

Newton’s laws of motion help us to describe the effects of force, mass, and acceleration on objects as they move. Newton’s law of inertia tells us that, due to inertia, an object at rest will remain at rest and an object will stay in motion with the same speed and direction unless unbalanced forces act on either object. Newton’s law of force and acceleration gives us the mathematical expression F = ma, which is used to calculate how force can influence an object’s motion based on its mass and acceleration. Newton’s law of action-reaction tells us that, whenever a force acts, an equal and opposite reaction happens together on both sides of the objects. 1.

Given the following scenarios, draw a free-body diagram of each scenario, labeling the forces acting on each object and the directions in which those forces are going.

A bowling ball being dropped off the Empire State Building:

A person jumping out of a plane:

Calculate the amount of horizontal force needed to make a 0.4-kg soccer ball accelerate at 250 m/s2 when kicked.

A 1,500-kg truck is towed sideways out of a mud-hole with a force of 15,000 N. What is the acceleration of the tow truck needed to move this vehicle?

A truck with a mass of 30,000 kg is traveling down a Michigan highway at a speed of 32 m/s when it sees a roadblock and must come to a sudden stop in 13 seconds. Given a uniform acceleration, find the following: •

The braking force needed to stop the truck. (Hint: Divide the speed by the time it takes to stop to find the acceleration in m/s2.)

•

The distance traveled while the trucker is braking.

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PS8BC Newton’s Three Laws and Force of Gravity

Math Connections 5.

In a vacuum, if a 0.045-kg golf ball is accelerated upward at 2.5 m/s2 by a hair dryer, how much force is required to accelerate the ball?

David’s car has a mass of 2,000 kg, and it produces a force of 5,000 N. How fast will the car accelerate? How can you increase the acceleration of the car with the same amount of force?

During the summer, mosquitos swarm, and cars driving on the highways get covered in bugs. Which of the two forces is greater: the force on the mosquitos or the force on the cars?

If a large truck and a small car collide and experience the same force, what might explain the increase in damage of the smaller car the farther away it is from the impact of the crash?

Use the following information to answer questions 9–10: In a crash test, cars hit a wall with varying amounts of force. The action and reaction forces are recorded in the table below. 9.

Create a graph relating the action force and the reaction force on the grid below to the right. Trail Number 1 2 3 4 5

Action Force of Car on Wall (N) 87,000 87,500 88,000 89,000 90,000

Reaction Force of Wall on Car (N) 87,000 87,500 88,000 89,000 90,000

10. Using x to represent the action force and y to represent the reaction force, create an equation to describe their relationship according to Newton’s law of force and acceleration.

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PS8BC Newtons’ Three Laws and Force of Gravity

Writing Science Name:

Date:

LOOK

THINK Think about examples from everyday life that demonstrate Newton’s Three Laws of Motion. WRITE Describe Newton’s Three Laws of Motion. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar.

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PS8BC Newtons’ Three Laws and Force of Gravity

Writing Science Topic:

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Physical Science

PS8D

Work, Mechanical Advantage, and Simple Machines

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PS8D Work, Mechanical Advantage, and Simple Machines

Student Handout Name:

Date:

Energy is measured by the ability to do work and cause change. In order to cause change, a force must be applied. Work measures how much force is required to move an object a distance while applying the force. In other words, work (J) = force (N) x distance (m). If a force is applied on an object and the object does not move, then no work was done on that object. Try these examples: 1.

Push a large book across the surface of your table. Did you do work on the book? Why or why not?

Lift a large book up into the air. Did you do work on the book? Why or why not?

Roll a small ball across the table. Did you do work on the ball? Why or why not?

Push down on the table with your hand. Did you do work on the table? Why or why not?

Work, like energy, is measured in joules (J), and 1 joule causes change when 1 newton of force is applied on an object and it moves 1 meter.

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PS8D Work, Mechanical Advantage, and Simple Machines

Student Journal Name:

Date:

Group:

Situations of Forces Background 1.

Define work.

What is the formula for calculating work? __________________________________________

What must occur in order for work to be done?

_______________________________________________________________________________ _______________________________________________________________________________ 5. If a student places a finger on a pencil and pushes with 75 newtons of force straight down, but the pencil does not move, how much work is done? Why? _______________________________________________________________________________ _______________________________________________________________________________ 6. Work the following problems. Make sure to show your work! A student pushes a pencil on the table with a force of 50 newtons. The pencil moves 0.25 m across the table. How much work is done?

The same student pushes the same pencil with a total of 50 newtons of force. The pencil moves 0.3 m. How much work is done? 7.

In the two problems from question 6, more work is done in which situation? Explain why.

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PS8D Work, Mechanical Advantage, and Simple Machines

Student Journal Part I: Plan Your Investigation 1.

My question of inquiry:

_______________________________________________________________________________ _______________________________________________________________________________ 2.

The hypothesis:

What is the independent variable (also known as the manipulated variable)?

_______________________________________________________________________________ _______________________________________________________________________________ 4.

What is the dependent variable (also known as the responding variable)?

_______________________________________________________________________________ _______________________________________________________________________________ 5.

Is there a control group or control variable for this investigation? Explain.

_______________________________________________________________________________ _______________________________________________________________________________ 6.

What materials, equipment and technology will be needed for this investigation?

List all safety precautions that must be taken.

Follow the procedures listed in the Student Guide to conduct this investigation.

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Student Journal

PS8D Work, Mechanical Advantage, and Simple Machines

Part II: Implement Your Investigation Collect, Record, and Organize Data Work Without a Simple Machine Moving a 200-g Mass to 0.1 m Directly Above a Surface Force (N)

Distance (m)

Work (J) W=F x d

0.1 m 0.1 m 0.1 m Average =

Average = 0.1 m

Average =

Work With a Simple Machine Moving a 200-g Mass to 0.1 m Directly Above a Surface Force (N) Trial 1

Trial 2

Trial 3

Average Force

Distance (m)

Work (J) W=F x d

0.6 m 0.4 m 0.2 m 0m

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PS8D Work, Mechanical Advantage, and Simple Machines

Student Journal Part II: Implement Your Investigation, continued

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Student Journal

PS8D Work, Mechanical Advantage, and Simple Machines

Part II: Implement Your Investigation, continued Analyze Data 1.

What happens to the amount of force it takes to pull a mass up a ramp when you increase the length of the ramp?

_______________________________________________________________________________ _______________________________________________________________________________ 2.

Why did the amount of work stay the same when the length of the ramp changed? Explain your answer.

_______________________________________________________________________________ _______________________________________________________________________________ 3.

When you pulled on the mass and it did not move, explain why work was not done.

_______________________________________________________________________________ _______________________________________________________________________________ 4.

Predict the amount of force it would take to pull a 200-g mass up a ramp that is 0.5 m.

_______________________________________________________________________________ _______________________________________________________________________________ 5.

What was the purpose of the waxed paper?

_______________________________________________________________________________ _______________________________________________________________________________ 6.

If you were pulling a larger mass, would you expect your results to be different? Explain.

_______________________________________________________________________________ _______________________________________________________________________________ 7.

How much work would be accomplished in joules if the 200 g mass required two newtons of force to move to a distance of 0.2 m above the table surface? Show your calculations.

Which ramp would you choose to move the mass to a height of 0.2 m above the table surface, the 0.6 m, 0.4 m, or 0.2 m length? Why?

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Student Journal Reflections and Conclusions 1.

Is the hypothesis supported by the data? Explain.

How did the results reveal a relationship between the independent and dependent variable?

Where could have errors been made while collecting or organizing data?

What do you conclude about this investigation?

What would you do differently if you were to conduct this experiment again?

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STEMscopedia: WORK, MECHANICAL

ADVANTAGE, AND SIMPLE MACHINES PS8D

Reflect Once upon a time, there was a family of six people and two dogs moving to a new city across the country. The family had a lot of “stuff,” so when the movers showed up to load the heavy furniture and all the boxes, there was a team of four movers who were sent to tackle the job. There were three very large muscular men and one small man on the moving squad. The three large men sweated, lifted, and carried many pieces of heavy furniture successfully, using teamwork and brute strength. Guess who moved the most heavy furniture and boxes? It was the captain of the group, the small man. How did he do it? He was equipped with a dolly, and he knew how to use it to make the most of its mechanical advantage. He was faster and more efficient. He loaded the dolly and rolled it with much less effort than his teammates used to lift and carry everything. That one machine made him faster and stronger than his counterparts. Read on to find out how simple machines work and how mechanical advantage helps people.

Look Out When a friend declares that she got a lot of work done, she might mean that she studied for several hours for a test, finished a history paper for school, or memorized all her lines for her role in the school play. It would be true that she accomplished a great deal of work, unless she was speaking scientifically. The scientific definition for work possesses a very different meaning than the common usage of the word work. The non-scientific definition of work has several definitions including: 1) employment; 2) activity involving physical or mental effort; and 3) something functioning properly. The scientific definition for work is: using a force to move an object a distance. The mathematical formula is W = Fd (meaning work equals force multiplied by distance). Work As you have learned, work is using a force to move an object a distance. The formula W=Fd means work equals the force applied multiplied by the distance moved. It is important to note that not all forces do work. Sometimes a force is directed at an object, but no work is done. Consider the following example. You go into a weight room and put forth your best effort to lift a 300 pound weight. You strain and sweat and pull and lift for 10 minutes to no avail. The weight does not budge at all. You have expended effort and energy, but you have not accomplished any work in the scientific sense. Why? Simply stated, you did not move the weight. Since the distance moved is zero, when you apply the formula W=Fd to the situation, W=0. The distance (zero) multiplied by any force at all will be zero, so the work done is also zero.

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Mechanical Advantage Mechanical advantage is the ratio of output force to input force. Like work, mechanical advantage has a formula. It is MA=Fo/Fi, which means mechanical advantage equals the output force of a machine divided by the input force to the machine. Mechanical advantage is a ratio, so it does not use units. It is a measure of how much force you are applying multiplied by the machine. In other words, it helps to assess the performance and usefulness of a machine. Efficiency Efficiency is a percentage of how productive a machine is with the work input with which it is supplied. Efficiency is work output divided by work input multiplied by 100. The formula for efficiency is (Work Output/Work Input) x100. It also helps to assess the performance and usefulness of a machine. An ideal machine would run with 100 percent efficiency. The work put into a machine would equal the work put out by the machine. However, on Earth, machines are never able to achieve 100 percent efficiency. What actually happens is that work input is always greater than work output. Why is this? Some of the work put into the machine is always lost to heat energy due to friction. Hint: Mechanical advantage and efficiency are easily confused. Mechanical advantage is a measure of how much your force is increased by the machine you are using, while efficiency is a measure of how much of your work truly goes to moving the object you are attempting to move. Also, mechanical advantage is expressed as a ratio, while efficiency is expressed as a percentage. Helpful Terms There are three more terms you should learn to make simple machines more meaningful. • energy: the ability to do work • resistance: the force a machine has to overcome to do work • effort: the force applied to a machine to overcome resistance and do work What Do You Know? Scientists and inventors throughout modern history have dreamed of creating a perfectly efficient machine called a perpetual motion machine. A perpetual motion machine is a contraption that would be set in motion once and would then stay in constant motion, never stopping. Thousands of these machines have been imagined, designed, and constructed over the last couple of centuries, but none have worked. Think about the following design of a perpetual machine. A generator transforms mechanical energy into electrical energy and sends the electrical energy to power a motor. The motor in turn changes the electrical energy into mechanical energy and transmits the mechanical energy back to the generator. Once again, the generator alters the mechanical energy to electrical energy and directs it to the motor. The cycle continues indefinitely.

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STEMscopedia: WORK, MECHANICAL

ADVANTAGE, AND SIMPLE MACHINES

Answer the following questions using the information from the scenario above and your knowledge of efficiency. Be prepared to discuss your thoughts.

Will this perpetual motion design work? Why?

Can there ever be a perpetual motion machine that works on Earth? Why?

Can there ever be a perpetual motion machine that works anywhere in the universe? Why?

Simple Machines Scientifically speaking, a machine is defined as an apparatus that transfers mechanical energy from one object to another object. A great benefit of machines is that they reduce the effort needed to overcome resistance. In other words, they make life easier for people by causing the same effort to result in more work being accomplished. Machines work by changing any or all of the following: • • •

the direction of an applied force the amount of an applied force the distance over which a force is applied

A simple machine is a device that uses only one motion to transfer mechanical energy. There are six types of simple machines: levers, pulleys, wheels and axles, inclined planes, wedges, and screws. A lever is a rigid bar that pivots around a fulcrum. A lever makes work easier because it amplifies the applied force (effort). There are three categories of levers, classified based upon where the effort, resistance, and fulcrum are located. (To more thoroughly explore the types of levers, see the What Do You Think? section.) Examples of levers include rulers, brooms, scissors, crowbars, hammers, staplers, seesaws, shovels, and salad tongs. A pulley is a simple machine composed of a rope and one or more wheels. The wheel or wheels are grooved, and the rope fits into the grooves. Generally, a pulley is used to lift heavy weights. Resistance is located either at one end of the rope or a wheel, and the effort is applied to the opposite end of the rope. Just as with levers, there are three types of pulleys: fixed pulleys, movable pulleys, and compound pulleys.

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ADVANTAGE, AND SIMPLE MACHINES

•

Fixed pulleys do not move. Fixed pulleys change the direction of the effort force, but they do not increase the effort force. An example of a fixed pulley is a flagpole. • Movable pulleys move with loads. They work by causing the work force to be less than the effort. An example of a movable pulley is a weight-lifting machine at a gym. • Compound pulleys have multiple wheels and dramatically decrease the effort needed to lift the load. Combined pulleys accomplish this by increasing the distance required to move the load. An example of a combined pulley is a block and tackle.

A wheel and axle is a round wheel attached to a cylinder so that both parts rotate together. It reduces necessary effort because effort is applied to the wheel using a greater distance and the force is multiplied in the axle. Examples of wheels and axles include doorknobs, car wheels, rolling pins, and windmills. An inclined plane is a flat surface where one side is higher than the other. An inclined plane decreases the force needed to move an object by increasing the distance traveled. Examples of inclined planes include wheelchair ramps, switchbacks on mountain trails, stairs, and loading ramps on moving trucks. A wedge is an inclined plane that can be driven into something to separate it or in between two things to split them apart. The effort is applied by forcing the wedge into an object or between two objects. Examples of wedges include axes, knives, saws, and ice picks. However, wedges are not only used to push or split objects apart. They can also function to hold objects together. Examples of these such wedges include staples, tacks, nails, and doorstops. An axe uses force to split objects apart.

Staples are wedges that hold objects together. A screw is an inclined plane wrapped around a cylinder. A circular force is applied to the head of the screw in order to overcome the resistance of the surface the point of the screw is working to penetrate. The distance is increased so the required force can be decreased.

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STEMscopedia: WORK, MECHANICAL

ADVANTAGE, AND SIMPLE MACHINES

What Do You Think? As was mentioned in the section above about levers, there are three different classes of levers. The classification of types depends upon where the effort, fulcrum, and resistance are located on the levers. • • •

First-class levers have the fulcrum located between the forces of the effort and the resistance. E___________F______R Second-class levers have the fulcrum on one end of the lever, the effort being applied on the other end of the lever, and the resistance occurring in the middle. E____________R_____F Third-class levers have the fulcrum positioned on one end, the resistance on the other end, and the effort occurring in the middle. F_____E____________R

Look at the following pictures of levers, analyze how they are utilized, and classify them as first, second, or third class. Check the table at the end of the Stemscopedia to see if you were correct.

_______________ ________________ _______________

________________ __________________ __________________

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Complex Machines A complex machine is an apparatus that is composed of at least two simple machines. For example, a bicycle is made of several simple machines, consisting of: • wheel and axle (handlebars) • screw (bolts on the wheels and the seat) • pulley (chain) • lever (kickstand) • lever (hand brakes) • wheel and axle (wheels) Obviously, many modern and high-tech machines are much more complex than bicycles and contain computer chips, but they are still created utilizing multiple simple machines. Examples of other complex machines include cars, computers, elevators, dishwashers, washing machines, televisions, and stereos.

To help your child see how prevalent simple machines are in our lives, take a “Simple Machine Tour” through your house.

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STEMscopedia: WORK, MECHANICAL

ADVANTAGE, AND SIMPLE MACHINES

Connecting With Your Child 1. Locate and write down at least two of each type of simple machine. Note what the object is and which simple machine it is. Object

Simple Machine lever lever pulley pulley wheel and axle wheel and axle inclined plane inclined plane wedge wedge screw screw

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STEMscopedia: WORK, MECHANICAL

ADVANTAGE, AND SIMPLE MACHINES

2. Locate and write down at least three complex machines (a machine composed of two or more simple machines). Then record the simple machines contained in the complex machine. Complex Machine

Simple Machine Components

3. Answer the following questions about your “Simple Machine Tour.” • Which simple machine was the most common to find? Why? • Which simple machines were most rare and most difficult to find? Why do you think so? • Do you think there are any drawbacks to simple or complex machines? If so, what are they? Why do you think so?

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PS8D Work, Mechanical Advantage, and Simple Machines

Reading Science Name:

Date:

Group:

Harnessing Kinetic Energy 1

The definition of energy in physics is the ability to cause change or do work. Energy comes in two basic varieties: potential and kinetic. Potential energy is the energy stored in an object or a field. It can be gravitational, elastic, or chemical. Kinetic energy is energy due to motion. It can be vibrational, rotational, or translational. Kinetic energy and potential energy are scalar quantities; they only have magnitude, not direction. Humans have harnessed potential and kinetic energy for thousands of years.

One of the earliest examples of replacing human muscle power with a machine is the sail. The earliest depictions of sails come from Egypt around 3200 BCE. The Egyptians sailed the river Nile. The earliest sail designs were square sails mounted on a yardarm perpendicular to the boat’s hull. The kinetic energy of wind pushes on the sail, imparting kinetic energy to the boat. This causes the boat to move in the same direction as the wind is blowing.

Other machines transform potential and kinetic energy. Water near the river’s headwater has more gravitational potential energy than water further downstream. Flowing water transforms the gravitational potential energy to kinetic energy. The earliest examples of water mills date back to the third century BCE. Water mills ground grain. The kinetic energy contained in flowing water was transferred to the water wheel. The wheel in turn rotated a shaft, which ultimately turned a millstone. Water mills were most efficient when located on a constantly flowing river or near the bottom of a hill from which water could be piped to the wheel. Water turbines are modern ways to harness water’s energy. The water behind a dam has gravitational potential energy. When it flows across turbines, the potential energy is converted to kinetic energy. The turbine turns, generating electricity.

Wind turbines are a modern method for harnessing the energy contained in moving air. Air pressure varies across Earth. Differences in air pressure in different locations cause air movement. Moving air turns the wind turbines. Turning the wind turbines generates electricity. Wind turbines are designed to be lightweight and have little resistance to rotation. Both of these factors allow them to convert wind energy to electricity more efficiently.

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Reading Science 5

Water flows downhill due to a difference in gravitational potential energy. Another type of potential energy is elastic. A stretched rubber band is an example of elastic potential energy. The kinetic energy harnessed by water mills, water turbines, and wind turbines is translational. Water or air is moving across a distance. Since water wheels, water turbines, and wind turbines rotate, they are examples of rotational kinetic energy. Vibrational kinetic energy is either desirable or undesirable. The vibration of the reed in a woodwind instrument is essential for its function. The vibrations causing noise in engines generally waste energy and make the engine less efficient.

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PS8D Work, Mechanical Advantage, and Simple Machines

Reading Science 1.

Sails on sail boats take advantage of which type of energy? A.

Potential energy of air

Kinetic energy of air

Potential energy of water

Friction of water

Flowing water can do work due to its _________ energy. A.

kinetic

potential

gravitational

elastic

Which of the following items is most like a wind turbine? A.

Pinwheel

Car wheel

Sail

Bicycle tire

What type of kinetic energy does flowing water have? A.

Rotational

Vibrational

Translational

Chemical

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Reading Science 5.

Which of the following is an example of elastic potential energy? A.

Water stored behind a dam

A wind turbine moving slowly

A book lying on a table above a floor

A stretched rubber band held between two hands

You are comparing two nearly identical engines. One runs extremely smoothly with very little noise. The other produces very loud noises. All other factors being equal, which engine likely converts more of the fuel to work? A.

The noisy engine

The quiet engine

Both engines would produce the same amount of work for a given amount of fuel.

Not enough information is provided to answer the question.

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PS8D Work, Mechanical Advantage, and Simple Machines

Math Connections Name:

Date:

The work it takes to move a 20-kg box up a frictionless ramp is the same as it would take without a ramp; however, the force needed to move the object decreases with a ramp. The table below shows the measure of each angle of a ramp, the length of each side, the work based on the distance of side A (no ramp), and the force needed with and without a ramp. Fill in the missing information. (The first one has been done for you.)

Ramp Ex.

Work Required m = 20 kg

Force (no ramp) m = 20 kg

Force (with Ramp) m = 20 kg

1: 90o

A: 2

F = 392 / 2

F = 392 / 4

2: 60

B: 3.5

(2)(9.8)(20)

F = 196 N

F = 98 N

3: 30o

C: 4

W = 392 J

1: 90

A: 3.5

Sketch of Triangle

1 B

Force = (mass) x (9.8) Side Length

Work = Force x Distance

Angle Measure

Group:

2: _____

B: _____

3: 45o

C: 5

1: _____

A: 0.87

2: 80º

B: 4.9

3: 10o

C: 5

1: 90

A: 3.8

2: 20o

B: 1.4

3: _____

C: 4

1: 90

A: 3.2

2: 50o

B: 3.8

3: _____

C: 5

What effect did the height of the incline have on the amount of work that had to be done?

What effect did the steepness of the incline have on the force required to move the object?

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Math Connections A pulley system consists of a rope attached to a wheel and a load. Pulleys distribute the weight of the load over different sections of the rope. They reduce the force needed to lift the load by increasing the distance the load is moved. To the right are three examples of pulleys. Michael needs to choose one of these machines to lift a 200-N box at a constant rate.

System C

What force does the box exert on the pulley? Description

System B

Picture

Use this information to answer the questions that follow.

System A

Michael is pulling 100 N, because Michael is pulling Michael would be the remaining 200 N with the pulling less than force would be pulley system. 100 N. pulled by the two smaller pulleys.

In System B, the two pulleys are the same size. If Michael is pulling 100 N, with which equation can we calculate the forces exerted by one of the pulleys on the box? Circle one: a.

(200 – 100) / 2

200 – 100

200 / 2

(200 – 100) x 2

In pulley system B, what is the force each pulley exerts?

10. Though System C also has two pulleys, why does it let Michael pull with less than 100 N?

11. Explain and draw a picture of a different pulley system that may let Michael pull less weight. (Use a separate sheet of paper.)

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PS8D Work, Mechnical Advantage, and Simple Machines

Writing Science Name:

Date:

LOOK

THINK Work done on an object is equal to the product of the force and the object’s displacement. Cranes have been used since ancient times. The first cranes were made of wood and powered by either humans or animals. During the Industrial Revolution, iron and steel became the materials of choice. Modern cranes use either gasoline engines or electric motors and hydraulics to move loads. In physics, no work is done without motion. So a classmate pushing against a wall may become tired, but she is doing no work if she cannot move the wall. Work is done on an object only in the direction of displacement. Remember also potential and kinetic energy. Consider the crane and its load to be a system. The load weighs 230 kg. The load started at ground level and was raised to a height of 5 m. The final destination of the load is displaced 5 m vertically and 10 m horizontally from its starting point. WRITE Using physics vocabulary, describe the work and energy transformation in the situation above. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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Writing Science Topic:

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Physical Science

PS9AB

Electromagnetic and Mechanical Waves

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PS9AB Electromagnetic and Mechanical Waves

Student Handout Name:

Date:

Waves All Around 1.

Brainstorm with your group to make a list of waves. Your list may include types of waves or technology that uses waves. You have five minutes to complete this task.

Write your list of waves in your lab journal.

Share one item on your group list when asked by your teacher.

As other groups share items from their lists, check your list and add the item, if appropriate.

Now decide whether each of these examples would be able to move through matter or move through the vacuum of space. Moves Through Matter

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Moves Through Space

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PS9AB Electromagnetic and Mechanical Waves

Student Journal Name:

Date:

Group:

Background: Understanding Waves 1.

Draw three wave forms: one with a high frequency and low amplitude, one with a long wavelength and high amplitude, and one with a low frequency and low amplitude. Label each and compare their properties. For one of the waves, label crest and trough.

Write the wave equation and identify its variables.

What is the relationship between a wave’s frequency and its wavelength?

What is the relationship between amplitude and velocity? Explain.

Define medium and vacuum.

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PS9AB Electromagnetic and Mechanical Waves

Student Journal Part I: Plan Your Investigation 1.

My question of inquiry:

_______________________________________________________________________________ _______________________________________________________________________________ 2.

What do you need to do to answer this question?

What are the variables that you will observe?

_______________________________________________________________________________ _______________________________________________________________________________ 4.

What do you predict will occur?

_______________________________________________________________________________ _______________________________________________________________________________ 5.

What materials, equipment, and technology will you need for this investigation?

What safety precautions must be taken in this investigation?

Record your procedure on the back of this worksheet or in your lab journal, if needed.

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PS9AB Electromagnetic and Mechanical Waves

Student Journal Part II: Implement Your Investigation Collect, Record, and Organize Data

For each wave, identify or calculate each variable in the wave equation based on your data.

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PS9AB Electromagnetic and Mechanical Waves

Student Journal Part II: Implement Your Investigation, continued Analyze Data 1.

Describe each of your waves using amplitude, wavelength, frequency, velocity, and period.

Compare and contrast one of your waves with that of another group generated during the same music. Explain any similarities or differences.

What is the relationship between the oscillations of the marker and the amplitude of the wave you recorded?

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PS9AB Electromagnetic and Mechanical Waves

Student Journal Reflections and Conclusions 1.

Was your prediction correct or incorrect? Explain.

Was there a relationship between the variables you observed?

List and briefly describe the sources of error in this experiment.

What do you conclude about this investigation?

What would you do differently if you were to conduct this experiment again?

Using all of the following terms, develop a graphic organizer on a separate sheet of paper based on what you have learned in this Explore.

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Student Journal Additional Practice-Show your work and remember labels A.

What is the velocity of a wave with a frequency of 1.8 Hz and a wavelength of 3.6 m?

You are standing 80 m from the base of a canyon and you scream, “Echo!” If the sound travels at 343 m/s, when will you hear the echo?

A wave has a wavelength of 1.4 x 10-6 m and a frequency of 5.0 x 107 Hz. What is the velocity of this wave?

What is the wavelength of a wave with a frequency of 4.5 x 107 Hz and a velocity of 55 m/s?

What is the frequency of a wave with a velocity of 48 m/s and a wavelength of 1.4 x 10-7 m?

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STEMscopedia: ELECTROMAGNETIC AND

MECHANICAL WAVES

PS9AB

Reflect Have you ever watched waves flow against the shore at a beach? As the wave approaches the shore, the water moves up and down in a continual cycle. Each up-and-down cycle makes up a single wave. Another type of wave you may have seen travels along the length of a spring. If you compress and release one end of a spring quickly, a pulse travels along the spring. This pulse causes the spring to become compressed in some parts and stretched in others. The up-and-down motion of water at a beach and the compressed pulse that travels along a spring are both examples of waves. How are they similar? How do they differ? Of course, they travel through different substances—water versus metal—but think about how else these wave types are different. Transverse and Longitudinal Waves While there are many different types of waves, they can all be classified into one of two categories: transverse and longitudinal waves. We classify waves into one category or the other by comparing the direction the wave moves to the direction of the particles that transmit the wave. Transverse waves travel perpendicular to the displacement. To understand transverse waves, think again about a wave that travels through the water at a beach. You can think of the up-and- down motion of the water as the wave disturbance. (More specifically, the energy of the wave causes water molecules to move up and down as the wave travels toward the shore.) Now imagine you are on a boat with the open sea on your left and the shore on your right. As you watch the wave move, the wave disturbance travels from the open sea on your left to the shore on your right. This means the wave is propagating in the horizontal direction. However, the water molecules move up and down. This means the particles that transmit the wave are moving in the vertical direction. Thus, the wave travels perpendicular to the displacement. It is a transverse wave. You can create transverse waves on a long rope by tying one end to a tree and shaking the other end up and down perpendicular to the rope’s length, as shown at the top of the next page. A pulse will travel up and down at a right angle to the length of the rope as the wave travels. Other examples of transverse waves include electromagnetic waves. Transverse waves are described using the various parts of the wave. Look at the diagram below as we describe the parts. Looking at the diagram above, you will notice that the highest point of the wave is called the crest. The crest is the maximum positive displacement from the rest position. You can remember this by thinking of the water waves, the top of the wave is also called the crest. The rest position is the equilibrium of the wave; since it is not disturbed it is at rest. Just like when you are at rest, you remain undisturbed. If the crest is the maximum positive displacement, then we have to describe its opposite. The maximum negative displacement from the rest position is called the trough.

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You can think of the shape of a water trough for animals, to help you remember that it curves downward. Next is the amplitude of the wave. Amplitude is the distance from the crest position to the rest position or the rest position to the trough position. You can remember this by thinking of the amplitude in your stereo. You can turn your music all the way to bass, trough, or all the way to soprano, crest. The distance from the trough to the crest is called the wave height. Just like you, you measure from the bottom to the top to get your height. Lastly, wavelength is the distance from crest to crest or trough to trough to make one complete wave cycle. The amount of complete wave cycles in a certain amount of time determines the frequency of a wave. In contrast, longitudinal waves travel in the same direction as the displacement. Consider the spring mentioned earlier. When you compress one end quickly, the compressed pulse oscillates back and forth along the length of the spring. In this case, the spring pulse displacement oscillates horizontally along the spring, and the wave also travels horizontally. Thus, the wave travels in the same direction as the displacement. As the pulse propagates, it creates regions where the particles of the medium are very close together. These regions are called compressions. In between these compressions are regions where the particles are stretched farther apart. These regions are called rarefactions. All longitudinal waves are made of alternating compressions and rarefactions. Some common examples of longitudinal waves are sound waves and seismic waves. A longitudinal pulse travels along the length of a spring. The areas of the spring that are close together are called compressions. The areas that are farther apart are called rarefactions. A longitudinal pulse travels along the length of a spring. The areas of the spring that are close together are called compressions. The areas that are farther apart are called rarefactions.

What Do You Think? Waves A and B travel in the directions shown below. Are the waves transverse, longitudinal, or a mixture of both types? Check your answer on the next page. While the two waves move in opposite directions, they both move perpendicular to their displacement, so they are both transverse waves. Use the diagram to answer the following questions. Look at waves A and B.

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STEMscopedia: ELECTROMAGNETIC AND

MECHANICAL WAVES

Based on what you learned, answer the following questions. 1. Which wave occurs with the most frequency? 2. Which wave has the longest wavelength? 3. Which wave has the shortest wavelength? 4. What do you notice about the wavelength versus the frequency of the wave? 5. Based on the wavelength, which wave has greater energy? Mechanical Waves Mechanical waves are waves that travel through a material known as a medium. A medium is a solid, liquid, or gas made up of a particular type of particle. For example, air, water, and Earth’s crust are three different types of media. The vibrations of particles in the medium produce the mechanical wave. Both longitudinal and transverse mechanical waves can travel through a solid medium. Earthquakes, for instance, create both longitudinal and transverse waves that travel through the solid structure of Earth. Only longitudinal mechanical waves, however, can travel through fluids such as liquids and gases. (As you will learn, electromagnetic waves are transverse waves that can travel through fluids, but this is because electromagnetic waves are not mechanical. They do not require a medium at all.) Sound is a longitudinal wave that can travel through a fluid or a solid. You can hear voices in another room even with the door closed because the sound waves travel through the air, then through the solid door, and then again through the air to your ears.

Look Out Why can’t transverse mechanical waves travel through ﬂuids? A transverse mechanical wave can travel only through a medium that is relatively stiff or rigid, such as a rock or a rope. If the medium is not rigid enough, the particles in the medium can slip past each other, and a transverse wave cannot propagate. Water is a ﬂuid, so it should transmit only longitudinal waves. However, you have probably seen the motion of a buoy or boat bobbing up and down as waves pass by underneath. This motion seems to come from transverse waves. Are water waves longitudinal or transverse? The answer depends on whether the wave is on the surface of the water. The water below the surface can transmit only longitudinal waves. That is, the particles that transmit waves underwater can move back and forth only along the direction of the wave. Water particles on the surface, however, feel a different net force than particles below the surface. This force is known as surface tension. It causes the surface of the water to be “stiffer” than the water underneath, allowing transverse waves to travel along the surface of the water. Both longitudinal and transverse waves can travel across the water surface, but only longitudinal waves can travel beneath the surface.

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Electromagnetic Spectrum and Waves Some waves do not need a medium and can travel through a vacuum. However, some waves do not require a medium through which to travel. That is, some waves can travel through a vacuum. These waves are called electromagnetic waves (also known as radiation). An electromagnetic wave is composed of an oscillating electric field and an oscillating magnetic field. These fields oscillate perpendicular to the direction in which the wave travels. So electromagnetic waves are transverse waves. The electromagnetic spectrum consists of the range of all possible wave frequencies of electromagnetic waves. The electromagnetic spectrum includes visible light, along with infrared and ultraviolet light, gamma rays, x-rays, microwaves, and radio waves. Waves in the electromagnetic spectrum are organized by wavelength. A radio wave can be as long as a skyscraper. A gamma ray is smaller than the nucleus of an atom. Electromagnetic waves behave quite differently from mechanical waves. Vibrating particles in a medium transmit mechanical waves. Therefore, mechanical waves are limited by the properties of their medium. If there is no medium, the waves cannot transmit. This is why there is no sound in outer space. However, electromagnetic waves do not rely on the particles in a medium in order to travel. You can think of an electromagnetic wave as pure energy traveling through space. Because of this, electromagnetic waves can travel through all types of matter—solids, liquids, and gases—as well as empty space. Furthermore, while mechanical waves are caused by disturbances in a medium, vibrating charged particles emit electromagnetic waves. For example, the charged particles in the atoms in our bodies are constantly vibrating. They emit infrared radiation, which is the type of electromagnetic wave commonly associated with the temperature of objects. This is how “night vision” goggles can detect the location of people even when no visible light is available. Another difference between mechanical and electromagnetic waves is that mechanical waves tend to travel relatively slowly compared to electromagnetic waves. The speed of sound is 343 meters a second at 20 degrees Celsius. Electromagnetic waves travel through a vacuum at a speed of 3.00 × 108 meters per second. (This is light speed. Nothing in the known universe travels more quickly than light.) A wave of light from the Sun reaches Earth in about eight minutes. Everyday Life: Electromagnetic Waves All Around Us You use electromagnetic waves all the time in your everyday life. Visible light waves are electromagnetic waves, so our vision depends entirely on light waves that travel from objects to our eyes. Cell phones, wireless Internet routers, remote controls, speed detectors, radios, and televisions transmit signals via radio waves and microwaves. Microwave ovens use microwaves to cook food, and many common heaters emit infrared radiation. Furthermore, doctors and dentists use x-rays to take images of their patients during examinations.

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Electromagnetic waves can also be harmful. Ultraviolet (UV) rays from the Sun can cause our skin to burn and kill bacteria. We take advantage of this property when we use UV rays to sterilize drinking water. Gamma rays and other high-energy waves emitted by radioactive materials can cause serious mutations, cancer, and even death.

Try Now Compare mechanical waves and electromagnetic waves by writing each description in the correct place in the Venn diagram below. Descriptions of Waves • longitudinal

• travels through different media

• transverse

• travels through a vacuum

• sound wave

• travels as disturbance of a medium • travels as disturbance of electric and magnetic ﬁelds

• wave on a string • visible light • microwaves

Mechanical Waves

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Electromagnetic Waves

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Connecting With Your Child Sound Waves on a Wire Help your child investigate sound waves by experimenting with variations of a simple “tin can telephone.” For materials, you will need two objects to use as telephone “receivers.” (You can use empty cans, each with an opening at one end, or two polystyrene cups.) Your child should connect the two receivers with string, twine, or wire. For example, you can punch a small hole in the closed end of each receiver and pass the line through the holes. Then secure the line by tying a large knot or by taping the string to the inside of each cup. You and your child can then attempt to communicate with the telephone assembly. For example, you can talk into one receiver while your child listens at the other receiver. You can also attempt to play the line like a guitar string with one person listening at one end. Have your child modify the design of the telephone assembly to observe how the sound transmission changes. For example, your child can experiment with different materials or different lengths of string. Or your child can try holding the string at different tensions. Here some questions to discuss with your child: 1. How do the different materials or line tensions affect the transmitted sound? 2. How does the sound travel from one receiver to the other? 3. Do real telephones use similar technology to transmit sound or is the technology different?

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PS9AB Electromagnetic and Mechanical Waves

Reading Science Name:

Date:

Group:

The Resurgence of Amateur Radio 1

Radio waves are part of the electromagnetic spectrum and have wavelengths ranging from 100 km to 1 mm. The corresponding frequencies range from 3 Hz to 300 GHz. Propagation of radio waves depends on their frequency. Generally, frequencies above 30 MHz propagate line-of-sight. Line-of-sight means that antennas have to be within sight of each other. Radio waves penetrate walls, so indoor antennas work just fine. Radio waves with frequencies below 30 MHz rely on Earth’s ionosphere for propagation. The ionosphere is a part of the upper atmosphere that is ionized by solar radiation. It can refract and guide radio waves. Depending on the time of day and the Sun’s behavior (e.g., solar flares), radio waves may travel for longer or shorter distances around the globe.

All radio communications require certain common equipment. A receiver consists of an antenna, filters, and amplifiers. It converts signals from the antenna to a usable form. A transmitter produces radio waves with the help of an antenna. Other equipment used today often includes a computer for keeping track of messages and digital communication modes. Radio equipment is available from different retailers. However, many teens and adults can build their own basic components. For example, a receiver can be built from a sturdy plastic bottle, some insulated wire, a germanium diode, alligator clips, and a telephone handset. The transmitter would have to be built separately.

Radio communication does not require relay towers. Relay towers can be toppled by earthquakes or hurricanes. They can also be overloaded with messages during a disaster. When towers are unavailable, radio communication can be a lifesaver. Amateur radio operators become a critical part of communications. They are trained to participate in disaster response with emergency personnel.

Amateur radio operators are also known as “hams.” There are about two million hams active around the world. As of 2013, the number of licensed operators in the United States exceeds 700,000. More ham operators are licensed every year. Ham operators are amateurs, which means they cannot receive monetary compensation for their activities. Most ham operators are very knowledgeable about radios. Enthusiasts come together in clubs and associations, sharing knowledge and skills. Certain frequencies across the radio spectrum are set aside for ham operators around the world.

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Reading Science 5

Most ham operators use radios for fun. They enjoy communicating with people around the world and across town. Some even communicate with ham operators in space! Line-ofsight communication can be used by astronauts and equipment flown on the International Space Station (ISS). Ham radio operators on Earth can talk to astronauts or use ISS to relay a message to another ham radio operator on Earth. The relay works as long as both ham operators on Earth can see ISS at the same time. Others hunt for signals from unmanned spacecraft. In November 2011, NASA launched “Curiosity” aboard the NASA Mars Science Laboratory. Within hours of launch, ham operators in Germany pointed a large antenna at the sky. A computer aimed the antenna at the appropriate region of the sky. They picked up signals from the spacecraft on its way to Mars.

Occasionally, ham operators are asked to solve down-to-earth mysteries. Remote locking devices for cars use radio waves. Outside one department store, shoppers discovered that their remote locking devices did not work. Ham operators were brought in. They walked around with handheld antennas and a receiver. They discovered that strong stray radio signals emitted from the building interfered with the locking devices. Store personnel were alerted and repaired the offending equipment. By law, no one can transmit radio signals strong enough to interfere with other equipment nearby. Ham radio operators have fun in many ways!

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PS9AB Electromagnetic and Mechanical Waves

Reading Science 1.

How radio waves propagate depends on ______________. A.

their frequency

the antenna used to receive the signal

their amplitude

the gravitational force present at the receiving location

Line-of-sight propagation means that ______________. A.

both transmitter and receiver have to be outdoors

both antennas have to be within sight of each other

the Sun is visible, and the ionosphere is charged

radio waves skim along the ground between buildings

Radio communications are frequently used in emergencies because ______________. A.

most people carry radios with them at all times

relay equipment is readily available

towers are not required for relay

it is cheaper than other modes of communication

Amateur radio operators ______________. A.

number about two million worldwide

are mostly retired engineers

don’t require a license in most countries

can only use frequencies above 30 MHz

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Reading Science 5.

Amateur radio communication with the International Space Station ______________. A.

is only possible during nighttime hours

requires that the ISS is in line-of-sight with the radio on Earth

can only be used to talk to astronauts on the station

is blocked when sunspots are numerous

What conclusion can you draw from the last paragraph? A.

Ham operators like to set up their equipment in parking lots.

Many car owners forget to change the batteries in their remote locking devices.

Radio signals cannot penetrate glass doors.

Malfunctioning equipment can emit stray radio waves.

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PS9AB Electromagnetic and Mechanical Waves

Math Connections Name:

Date:

Group:

Longitudinal and Transverse Waves Use the following information to answer questions 1–6. Electromagnetic waves are produced by the vibrations of charged particles, which result in changes in electric and magnetic fields. Microwaves, radio waves, radar waves, visible light, ultraviolet rays, x-rays, and gamma rays are well-known frequencies of electromagnetic waves. Electromagnetic waves are described by their wavelength, frequency, speed, and period. •

The speed of the wave (v) can be calculated using the following equation: =v = λf where v is the speed (m/s), λ is the wavelength (m), and f is the frequency (Hz).

•

The period of the wave (T) can be calculated using the following equation: T = 1/f where T is the period (s), and f is the frequency (Hz).

A wave cycles up and down three times per second, and the distance between each wave is 1.7 m. Calculate the following: •

Frequency of the wave

•

Wavelength

•

Speed

A sound wave with a frequency of 320 Hz travels through air at 300 m/s. Calculate the wavelength.

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PS9AB Electromagnetic and Mechanical Waves

Math Connections 3.

A gamma ray is a high-energy, high-frequency electromagnetic wave that travels at the speed of light (3.0 × 108 m/s). Calculate the wavelength if the frequency of the wave is 1020 Hz.

The frequency of a longitudinal sound wave is 900 Hz, and the speed is 320 m/s. What is the wavelength?

Which color of visible light has a greater wavelength, red light or blue light?

Electromagnetic waves such as radio waves travel at the speed of light (3.0 × 108 m/s). Calculate the frequency of a wave with a wavelength of 2.5 m in megahertz (MHz). The conversion rate from MHz to Hz is 1:1,000,000.

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PS9AB Electromagnetic and Mechanical Waves

Writing Science Name:

Date:

LOOK

THINK Longitudinal and transverse waves are the two basic types of mechanical waves. Experiments on mechanical waves often use a wave tank. A simple wave tank consists of a rectangular pan of water with a clear flat bottom and sides, a light source hanging above the tank, and a screen underneath the tank. Waves are generated manually, using a variety of tools such as a straight bar, water droplets from an eye dropper, or fingers. Your task is to design an experiment and data collection to determine the answer to the following questions: • For a circular wave, is the speed of travel the same in all directions? • Is the speed the same near the center of the tank as at the edges? WRITE Using the wave tank described above, design an experiment to answer the stated questions. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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PS9AB Electromagnetic and Mechanical Waves

Writing Science Topic:

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Physical Science

PS9C

Wave Phenomena

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PS9C Wave Phenomena

Student Handout Name:

Date:

Part I 1.

Take the 24-oz plastic cup and look into the cup at an angle, so you can just barely see the edge of the bottom, but not the “X” written on the bottom.

Continue looking at an angle, and add water until you can see the “X.”

How much water did you add? _________________________ mL

Explain how you were able to see the “X” without looking straight into the cup.

Part II 1. Pour the water from the plastic cup back into the beaker. 2.

Place the pencil in the beaker.

Draw a diagram of a pencil in the glass of water.

Explain how the pencil looked in the glass of water and why.

Compare Parts I and II.

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PS9C Wave Phenomena

Student Journal Name:

Date:

Group:

Part I: Wave Stations Wave Station 1: Reflection Observe and record the reflection of a water wave and a light wave at various angles. Part A: Water Wave Reflections Centered on Barrier

From the Side

Part B: Light Wave Reflections Incident Angle (°)

Reflected Angle (°)

Wave Station 2: Interference Observe and record constructive and destructive interference on a spring. Constructive Interference

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Destructive Interference

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PS9C Wave Phenomena

Student Journal Wave Station 3: Refraction

Compare and record the visual effects of each medium in the beakers.

Wave Station 4: Diffraction

Diagram the diffraction of the light source (both light and dark areas), using colors, as it appeared using each method. Using Single-Slit Diffraction (pencils)

Using Multiple-Slit Diffraction (diffraction grating)

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PS9C Wave Phenomena

Student Journal Part II: Models Using the data collected from your investigations, write a definition and draw a diagram that helps illustrate how the activity shows that particular term. Be sure to include waves in your diagrams, so do not just draw the station setup. Wave Station 1: Reflection _____________________________________ _____________________________________ _____________________________________

Wave Station 2: Interference _____________________________________ _____________________________________ _____________________________________

Wave Station 3: Refraction _____________________________________ _____________________________________ _____________________________________

Wave Station 4: Diffraction _____________________________________ _____________________________________ _____________________________________

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PS9C Wave Phenomena

Student Journal Reflections and Conclusions 1.

Related to wave station 1, what is the relationship between the angle of incidence and the angle of reflection?

Related to wave station 2, if two light waves shine on the same spot, is the resulting light wave always brighter than either component wave? Why or why not?

Related to wave station 3, why did the different liquids vary in their effect on the appearance of the straws?

Related to wave station 4, which colors of white light diffracted the most and which diffracted the least? Hint: The further from the center, the more they diffracted.

Using all of the following terms, develop a graphic organizer.

Terms: waves, sound, visible light, behavior, reflection, refraction, diffraction, interference

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PS9C

Reflect Consider the following situations, and think about what they all have in common: • As a police siren approaches, the siren has a high pitch. Then, as the siren passes, its pitch sounds lower. • After a rainstorm, people can see a rainbow in the sky as the Sun emerges from behind clouds. • When a woman yells over a large canyon, she can hear an echo of her voice. • On a hot, sunny day, a distant location along a road appears to be wet. However, when one approaches the location, the road is completely dry.

Each of these situations is an example of wave behavior. Unlike particles, which move in straight lines, waves oscillate or vibrate as they travel through space and time. Wave motion produces some very interesting—and sometimes difficult to explain—phenomena in the world around us. This is partly due to our senses of sight and sound being dependent upon the behavior of two different types of waves: light waves and sound waves. Because waves can behave in unusual ways, we may sometimes be surprised or confused by what we are seeing or hearing. What are some different ways that waves can behave? How does our understanding of wave medium: a substance behavior help explain various phenomena in the world? through which a wave moves Reflection The most commonly observed wave behavior is reflection. You observe this phenomenon whenever you see your image in a mirror, a glass window, or on the surface of a lake. Reflection occurs whenever a wave strikes a boundary between two media, such as air and water, and then bounces back into the medium from which it originated. For example, when light travels through the air and strikes the surface of a lake, some of the light is reflected at this boundary. Light reflecting off a lake’s surface can cause a bright glare on a lake or an ocean on a sunny day. It is also the reason we can observe the images of objects in water. Similarly, sound waves reflect off surfaces, creating a reverberation—or an echo—effect.

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STEMscopedia: WAVE PHENOMENA The reflection of waves from a boundary is similar to the way a billiard ball strikes and bounces away from a wall. If a ball strikes a wall “head on” (meaning it is traveling perpendicular to the wall), the ball will bounce back in exactly the same direction from which it traveled. However, if a ball strikes a wall at an angle to the perpendicular (called the angle of incidence), it will bounce away from the wall at the same angle to the perpendicular (the angle of reflection). Waves behave in the same way, as shown below. In fact, this is called the law of reflection. While a wave’s direction changes during reflection, its speed does not.

Refraction A wave can also be transmitted through a boundary, meaning that it passes through the boundary from one medium to another. In fact, at most boundaries, part of the wave is reflected and part of it is transmitted. Most waves move at different speeds through different media. For example, light moves quickly through air but more slowly through water. Thus, waves change speeds as they transmit from one media to another. This change in speed usually causes a wave to refract, or bend, as it passes through the boundary. To understand how refraction happens, think of a light wave as a group of students marching shoulder to shoulder from the bottom left corner of a room to the top right corner. Imagine that the left side of the room is one medium, such as air, and the right side of the room is another medium, such as water. As they march diagonally across the room, they step at the same pace. However, once they pass over the boundary into the right side of the room, they begin to walk more slowly through the new medium. Because the entire group approaches the boundary at an angle, one person will cross the boundary first and begin walking more slowly on the right side but the rest of the group will continue walking at the faster pace on the left side. This will cause the line of students to swing into a new direction, pivoting around the first student to cross over the boundary. Then, as the remainder of the students pass into the slower medium, they will begin walking at the slower pace and the students will march in a straight line again.

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STEMscopedia: WAVE PHENOMENA Look Out A wave behaves in the same way as the marching students. If it transmits from one medium to another at an angle to the medium, it will refract and change directions. (Note that if it strikes the new medium “head on,” it will not change directions.) Refraction causes white light from the Sun to spread out into different colors as it passes from air into new media, such as water or glass. For example, the different wavelengths of sunlight all refract at different angles when they pass through a raindrop. This causes sunlight to spread out into a rainbow as it refracts through raindrops after a storm. Diffraction and Interference Have you ever watched water waves pass through a narrow slit in a barrier? When the waves pass through, they spread out radially. This is known as diffraction. For example, when a light bulb is turned on in a dark room, light waves spread out radially from the light bulb. However, once the waves have traveled a certain distance, they can be thought of as plane waves that move in parallel “sheets,” like in the image on the right. When a plane wave passes through a narrow slit or a barrier, the wave will act as though it is originating from a point source again. Thus, the wave spreads out, or diffracts. This can also happen when a wave approaches a solid barrier. In these cases, when the wave passes along any edge of the barrier, it will spread out radially around the barrier. In this way, waves will appear to “bend” around barriers. This is the reason you can hear sounds that are emitted from behind a wall or large building. An interesting aspect of wave behavior is that two waves can occupy the same space at the same time. This is called a superposition of waves. The same types of waves can superimpose whenever they cross paths through the same medium. For example, if two sound waves cross paths in the air, they will superimpose. When this happens, interference will occur. Interference is the net effect of two or more superimposed waves. Recall that the amplitude, or displacement, of a wave changes depending on where the wave is in its cycle. When the displacement of two waves is in the same direction, their amplitudes add together and constructive interference takes place. So if two identical sound waves interfere with each other, the amplitudes of the waves add together and the sound becomes louder. Similarly, if two identical light waves interfere, the amplitudes add together and the light appears brighter. Sometimes, however, two waves with very similar characteristics are out of phase with each other. (The phase of a wave simply refers to its position in the wave cycle.)

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Waves A and B are identical, meaning the parts of each wave are displaced in the same directions. When they cross paths, they interfere and the amplitude of each wave adds together. This is called constructive interference.

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STEMscopedia: WAVE PHENOMENA If two waves begin their cycles at the same time, for example, they will be in phase with each other. However, if one wave begins its cycle first and then another wave begins slightly later, the waves will be out of phase. In this case, when the waves interfere, the displacement of each wave might cancel the other one out. When the displacement of waves is in opposite directions, destructive interference takes place. Most waves in the real world are out of phase with each other to some extent. In these cases, there will always be some amount of constructive interference and some destructive interference when the waves cross paths. Waves A and B are similar but out of phase. The displacement of Wave A is always opposite that of Wave B. When the waves cross paths, they interfere but the amplitude of each wave cancels out the other. This is called destructive interference.

What Do You Think?

Two waves cross a path in a medium, as shown below. Determine whether the interference is constructive or destructive at each location indicated. A. B. C. D.

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STEMscopedia: WAVE PHENOMENA Connecting With Your Child Investigating Wave Behavior With a Spring To help students learn more about various wave behaviors—including reflection and interference—have them observe the behavior of a long spring. For this investigation, a helical spring is best, but a long traditional spring or a spring toy will also work. First, challenge your child to produce a transverse wave along the spring. This can be done by quickly moving one end of the spring up and down or left and right. A transverse pulse will then travel along the spring as a wave. A transverse wave moves perpendicular to the direction of its vibrations.

A transverse wave moves perpendicular to the direction of its vibrations.

To observe a reflected wave, have your child fix one end of the spring to a stationary object (such as a table). Then have your child produce a transverse pulse along the free end of the spring. He or she should notice that the pulse travels to the fixed end and is then reflected back to the free end. To observe interference, two people must hold opposite ends of the spring. To produce constructive interference, each person must produce a pulse in the same direction. For example, both people must move their hand up and then down to produce the pulse. Your child should notice that the waves add together when they meet, producing a pulse that is the sum of the height of each individual pulse. Similarly, to observe destructive inference, one person must produce a pulse that is in the opposite direction of the other pulse. For example, if one person moves his or her hand up and then down, the second person would move his or her hand down and then up. Your child should notice that the pulses cancel each other out when they meet. Here are some questions to discuss with your child: 1. What happens when you fix one end of the spring and then produce a single pulse on the free end? What is this called? 2. When two identical pulses are produced at each end of the spring, what happens when the pulses meet? What happens when the pulses are opposite one another? What is this called?

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PS9C Wave Phenomena

Reading Science Name:

Date:

Group:

Using Wave Interference to Peer Into Deep Space 1

Waves transfer energy through space or through a medium without transferring matter. Electromagnetic waves transfer energy through the entire spectrum of visible and invisible wavelengths without needing a medium. Mechanical waves must transfer energy through different media, such as gases (air), liquids (water), and solids (drum). Wave interference occurs when two waves meet and overlap. The energy from each wave mixes and forms a third wave through superposition, depending on the pattern of the original waves. Waves in the same phase will add to each other (constructive interference), while waves out of phase will cancel each other (destructive interference).

If the two wave crests line up, the two incoming waves are “in phase” and result in third wave that is double in size. If the two waves are out of phase, then the crest of one matches the troughs of the other, ultimately canceling each other. Sometimes the waves are partly out of phase, which results in a pattern of light and dark areas called interference fringes.

Astronomers adapt this principle in their use of radio interferometers made of arrays of widely separated parabolic telescope dishes (radio telescope antenna) connected by cable or fiber optics. Interferometry increases the total light collected and resolution. This process, called aperture synthesis, superposes the incoming waves from different telescopes. Waves in the same phase will add to each other, while waves that have opposite phases will cancel each other. This combined image is equivalent in resolution to a single telescope whose diameter is equal to the spacing of the two most distant radio antennas in the array. Astronomers will study the interference fringes in the images gathered by the array.

The Atacama Large Millimeter/submillimeter Array (ALMA) located in northern Chile is an enormous array of 66 parabola antennas spread out over 18.5 km to create a resolution equal to a single telescope of that same diameter. Shorter radio wavelengths are measured in millimeters and submillimeters. The ALMA can pick up images that optical telescopes cannot, such as dark regions of the universe where protogalaxies are found.

In summary, astronomers use interferometers to combine signals from multiple telescopes that function as one larger, more powerful instrument that can peer into deep space. Some interferometers also work with visible light waves such as the optical interferometers in the pair of Keck telescopes in Hawaii. Furthermore, certain radio telescopes are connected worldwide in a Very Long Baseline Array that images deep space objects with unprecedented clarity.

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PS9C Wave Phenomena

Reading Science 1.

Which wave type(s) must have a medium in which to transfer energy? A.

Mechanical waves

Electromagnetic waves

Both electromagnetic and mechanical waves

Neither electromagnetic nor mechanical waves

Waves that meet and combine in the same phase will produce ________. A.

constructive interference

destructive interference

both constructive and destructive interference

neither constructive nor destructive interference

Interferometry is based on the ________. A.

analysis of interference patterns from one radio telescope

study of interference patterns from multiple radio telescopes

use of optical images from multiple radio telescopes

use of optical images from one radio telescope

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PS9C Wave Phenomena

Reading Science 4.

The process of superposing incoming waves from different telescopes and interpreting the interference fringes is called ________. A.

baseline array

Very Large Baseline Array

phase synthesis

aperture synthesis

What is a real advancement in interferometry, beyond the capability of ALMA? A.

Radio telescopes with enlarged parabolic dishes

Optical telescopes that are connected worldwide

Radio telescopes that are connected worldwide

The ability to connect up to 100 radio telescopes

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PS9C Wave Phenomena

Math Connections Name:

Date:

Group:

Wave Behavior Use the following information to answer questions 1–8. Diffraction, reflection, refraction, resonance, and interference all describe different wave behaviors. Match the following words with their definitions. 1.

______ Diffraction

______ Reflection

______ Refraction

______ Resonance

______ Interference

a change in the direction of a wave

occurs when the frequency of forced vibrations on any object matches the object’s natural frequency, resulting in an increase in amplitude

the bending of a wave around a barrier

a pattern formed by the overlapping of two or more waves

the bouncing back of a particle or wave

What is the Doppler effect?

What happens to the conical angle of the shock wave of a supersonic aircraft when the aircraft gains speed?

Samantha in standing in front of a flat mirror. How far behind the mirror is Samantha’s image if she is 1.7 m tall and standing 8 m from the mirror?

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PS9C Wave Phenomena

Math Connections Use the following information to answer questions 9–10. Refraction is the bending of the path of a light wave as the wave passes through a boundary separating two media (e.g., air and water). We can measure how much the light refracts as it crosses the boundary. The incident ray shows the direction that light travels as it approaches the boundary. The refracted ray shows the direction that light travels after it crosses the boundary. The angle that the incident ray makes with the boundary surface is called the angle of incidence, and the angle that the refracted ray makes with the boundary surface is called the angle of refraction. θr = angle of refraction θi = angle of incidence

θr = θi

nsinθi = n’sinθr

n = index of refraction 9.

Krista is playing with the newly installed light beams in her front yard. She notices that one of the beams is aimed towards the front bedroom window at a 45° angle with the ground (n = 1.23; n’ = 1.54). Find the following: •

The angle to the ground (normal) of the light beam after the beam is refracted on the glass window (once sinθr is found, take the inverse to find θr)

•

The angle to the ground (normal) of the light beam after the beam exits the other side of the glass into the air

10. A shark is swimming around and looks up at a fish ahead at a 20° angle to the water’s surface (normal; n = 1.45). Answer the following: •

Can the shark see into the air? If so, what is the angle of the shark’s line of sight outside the water? (Hint: n’ = 100)

•

What if the angle between the shark’s line of sight to the fish and the surface of the water is 45°? Calculate the angle of the shark’s line of sight outside the water.

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PS9C Wave Phenomena

Writing Science Name:

Date:

LOOK

THINK Refraction depends on the incidence of light and the refractive indices of the media. Refraction happens when light passes from one transparent medium to another. When each medium has a different refractive index, the speed of light changes, and it bends. How much the light bends depends on two factors: the refractive index of each medium and the angle between the light beam and the line perpendicular to the surface separating the two mediums. As the refractive index of the second medium increases relative to the first, the refracted light beam comes closer to perpendicular. Hydrogel is a material that is very absorbent. When submerged in water, it will consist of about 99% water by weight. As part of an experiment, a middle school science class drops small pieces of dry hydrogel crystals into clear glasses of water at the beginning of class. When they return to the experiment after lunch, the crystals have disappeared!

WRITE Make a hypothesis about what happened to the crystals and devise an experiment to test your hypothesis.

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PS9C Wave Phenomena

Writing Science Topic:

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Physical Science

PS9DE

Sound and Light Waves

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PS9DE Sound and Light Waves

Student Handout Name:

Date:

Defining Wave Behavior Draw a diagram of a pencil in the glass of water.

Explain how the pencil looked in the glass of water and why.

Describe the sound a train makes as it gets closer to you, and describe the sound the train makes as it passes you. What is the name of this effect?

Explain what diffraction is and why it helps you hear someone who is not in the same room as you.

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PS9DE Sound And Light Waves

Student Journal Name:

Date:

Group:

Background: Wave Behaviors For each of the following terms, write a definition and draw a diagram that helps illustrate it. 1.

Reflection

___________________________________ ___________________________________ ___________________________________ 2.

Interference

__________________________________ __________________________________ __________________________________ 3.

Refraction

___________________________________ ___________________________________ ___________________________________ 4.

Diffraction

___________________________________ ___________________________________ ___________________________________ 5.

Resonance

___________________________________ ___________________________________ __________________________________ 6.

Doppler effect

___________________________________ ___________________________________ ___________________________________

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PS9DE Sound And Light Waves

Student Journal Part I: Wave Stations Wave Station 1: Reflection Observe and record the reflection of a water wave and light wave at various angles. Part A: Water Wave Reflections Centered on Barrier

From the Side

Part B: Light Wave Reflections Incident Angle (°)

Reflected Angle (°)

Wave Station 2: Interference Observe and record constructive and destructive interference on a spring. Constructive Interference

Destructive Interference

Wave Station 3: Refraction Compare and record the visual effects of each medium in the beakers.

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PS9DE Sound And Light Waves

Student Journal Part I: Wave Stations, continued Wave Station 4: Resonance Measure the wavelength of a resonance in a pipe. Speed of sound in air = 331 m/s + (0.6 m/s / oC air temperature) Air temperature: __________ Expected speed of sound: __________ Frequency

Resonances in Air Column Length of Air Column (cm) Wavelength

Speed of Sound

Wave Station 5: Doppler Effect Listen carefully to the source of the sound. Draw a diagram of the source of the sound and how it changes as it moves past you in terms of changing frequencies.

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PS9DE Sound And Light Waves

Student Journal Reflections and Conclusions 1.

Related to wave station 1, what is the relationship between the angle of incidence and the angle of reflection?

Related to wave station 2, if two light waves shine on the same spot, is the resulting light wave always brighter than either component wave? Why or why not?

Related to wave station 3, why did the different liquids vary in their effect on the appearance of the straws?

Related to wave station 4, was your measured speed of sound exactly equal to the expected speed of sound? If not, what factors might account for the discrepancy?

Related to wave station 5, explain why you heard varying frequencies of sound as the source came closer and further away from you.

Using all of the following terms, develop a graphic organizer. Use additional paper, if needed.

Terms: waves, sound, visible light, behavior, reflection, refraction, diffraction, interference, resonance, Doppler effect 414

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PS9DE Sound And Light Waves

Student Journal Critical Thinking and You Identify a career that uses one of the wave phenomena studied here, and describe how the phenomenon is applied in that career. Use additional paper, as needed.

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STEMscopedia: SOUND AND LIGHT WAVES PS9DE

Reflect Have you seen a crowd of sports fans performing the “wave” at a stadium? Section after section of spectators stand and raise their hands, giving the appearance of an ocean wave traveling around the circle of seats. Although the wave appears to move horizontally, nothing is transferred from fan to fan. The only motion is vertical as each person rises and then sits. How does the kind of “wave” you see at a sporting event resemble waves in nature such as water waves, sound waves, and light waves? How are they different? Waves are generated by oscillatory motions. Oscillatory motion describes back-and-forth or vibrating movements. This type of motion generates waves in some mediums. Many oscillating objects move in the pattern called simple harmonic motion. Weights bouncing on springs and pendulums are examples of simple harmonic motion. In both cases, an object (the weight or the pendulum bob) moves back and forth around a central, or equilibrium, point. Such motion follows Hooke’s law, which is given by the equation F=−kx. In this equation, F is the force that acts to restore the oscillating object to the equilibrium point, k is a constant, and x is the object’s distance, or displacement, from the equilibrium point. As the spring stretches or the pendulum rises, the restoring force increases until it becomes strong enough to turn the oscillating object around and pull it back toward the equilibrium point. For simple harmonic motion, a graph of an object’s displacement from equilibrium versus time produces a sine wave, shown at right. Waves on the surface of water resemble this shape. Even waves we cannot see—for example, sound waves—can be described in these terms. Sound waves are generated by oscillating objects such as a drum head, a tuning fork, or a stereo speaker. The waves travel through the air, or other mediums, as regions of high and low pressure. A graph of pressure versus time for a pure note of sound would also produce a sine wave.

A plot of displacement versus time for an object Waves are characterized by amplitude, wavelength, and frequency. oscillating with simple The highest point a wave reaches above equilibrium is its crest, and the harmonic motion generates lowest point a wave reaches below equilibrium is its trough. a wave with the shape you • A wave’s amplitude is the vertical distance from its equilibrium point see above. This shape to its crest. Therefore, amplitude equals half the vertical distance is known as a sine wave. from crest to trough. In sound waves, amplitude corresponds to The object moves equal loudness. The greater a wave’s amplitude, the louder the sound. distances from equilibrium in equal periods of time.

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STEMscopedia: SOUND AND LIGHT WAVES •

A wave’s wavelength is the distance between consecutive crests (or consecutive troughs). Wavelength is represented by the Greek letter lambda (λ). Wavelength determines which waves we can sense. Humans can hear sound waves with wavelengths between about 0.02 meters (high pitches) and 20 meters (low pitches). Humans can see light waves with wavelengths between about 4 × 10–7 meters (blue light) to 7 × 10–7 meters (red light).

•

Frequency (f) is a measure of the number of times a wave cycles per unit time (typically one second). Frequency is measured in units of hertz (Hz); 1 hertz equals one cycle per second (1/s, or s–1). Therefore, a wave with a frequency of 100 hertz cycles 100 times in one second. A wave completes one cycle when its entire wavelength passes a certain point. So frequency is also defined as the number of waves that pass a certain point in one second. Consider again the 100 hertz wave. In one second, 100 of these waves (measured from crest to crest) would pass a certain point. Waves with higher frequencies have more energy.

•

The reciprocal of frequency (1/f) is called a wave’s period (T). Period is a measure of the time it takes a wave to complete one cycle or to move the distance of one wavelength.

A wave’s speed (v) equals the product of its frequency and wavelength: v = fλ. A wave’s amplitude does not affect its speed or frequency. Medium and temperature affect the speed of sound. The material through which a wave travels affects its speed. For sound waves, the denser the material, the faster sound travels, as shown by the data in the table. Material

Speed of Sound (m/s)

Density (g/cm3)

Air at 20 degrees Celsius

343

0.00012

Water

1,484

1.0

Iron

5,120

7.9

Unlike sound, light can travel through empty space. The speed of light in a vacuum is an important physical constant and is equal to 3.00 × 108 meters per second. This number is the constant (c) in Einstein’s famous equation E = mc2. Einstein also concluded that nothing could travel faster than light speed.

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STEMscopedia: SOUND AND LIGHT WAVES Like sound, light travels more slowly in denser mediums. In air, light speed is slightly slower than in a vacuum. In water, it is slower still. In glass, it is even slower. As you can see in the diagram, the higher a wave’s frequency, the shorter its wavelength, and the lower a wave’s frequency, the longer its wavelength. Therefore, high-energy waves have shorter wavelengths than low-energy waves. Resonance Have you ever wondered why a tuned guitar string always produces a particular sound? No matter how quickly or forcefully you pluck the string, it produces the same pitch. The reason for this is called resonance. To understand resonance, you must know that sound waves with larger amplitudes produce louder sounds, while sound waves with smaller amplitudes produce softer sounds. Resonance occurs when an object or a system oscillates at a large amplitude only when it is oscillating at a certain frequency or frequencies. The frequencies that cause the system to oscillate at a large amplitude are called resonant frequencies. Resonance occurs when Consider the guitar string. When it is plucked, it will vibrate with a large a wave oscillates at its amplitude at its resonant frequency. This means that it will produce resonant frequency. At this a loud sound with one particular frequency, or pitch. The string may frequency, the wave will vibrate at other frequencies, but the amplitudes of those vibrations will have a large amplitude. be much smaller, so those frequencies of sound may be too soft to hear. Other musical instruments such as trumpets, flutes, and pianos work in the same way. For example, air will vibrate through chambers of a brass instrument at a particular set of resonant frequencies. The musician must vibrate his or her lips at one of these frequencies through the mouthpiece of the instrument in order to cause the air in the chambers to vibrate. If the musician does not vibrate his or her lips at one of these frequencies, the air will not vibrate very loudly, and no sound will be heard. Resonance is also observed in buildings and bridges. Different structures have resonant frequencies at which they will vibrate. Engineers must understand resonance to ensure that the wind does not cause the structure to vibrate at a resonant frequency and collapse. In 1940, the Tacoma Narrows Bridge in Washington state collapsed due to vibrations at resonant frequency. You can search for videos of the collapsing bridge online. The Doppler Effect Think about what happens when a police car moves past you. As the car approaches, its siren has a high-pitched sound. As the car passes, the siren’s pitch seems to decrease. This phenomenon is called the Doppler effect. The Doppler effect is the apparent change in frequency of a wave moving relative to an observer. It happens when the source of a wave is moving and an observer is standing still. It also happens when the observer is moving and the wave source is still.

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STEMscopedia: SOUND AND LIGHT WAVES If the police car were at rest, the siren would release sound waves at a particular frequency. Each wave would travel a particular distance before the next wave is released. The waves would move away from the car at the speed of sound in air. However, when a police car approaches a stationary observer, the source of the sound wave is moving relative to the observer. As a result, the apparent distance between each sound wave decreases. As this happens, it will appear to the observer that the sound waves are arriving more frequently. In other words, it will sound as though the frequency of the pitch is higher than it would be if the police car were stationary. Conversely, when the police car passes by and begins moving away from the observer, the distance between successive sound waves appears to increase. Thus, it will appear to the observer that the sound waves are arriving less frequently, so the siren’s pitch will sound lower. A police car with a siren moves to the right. Each circle represents a sound wave from the siren. As the siren moves toward an observer on the right, the distance between waves is shortened, so an observer will notice a higher-pitched frequency. An observer on the left will notice a lowerpitched frequency. The Doppler effect is commonly observed with sound waves, though it is also observed in water waves when objects such as boats or animals move through water. Furthermore, it is observed with light waves that are emitted from moving sources.

What Do You Think? An astronomer observing objects in deep space notices that electromagnetic radiation from a distant star appears to have a lower frequency than it is expected to have. This is called redshift because the frequency is shifted toward the red end of the visible light spectrum. What could redshift indicate about the motion of a star? Redshift is an example of the Doppler effect as it applies to visible light waves. As explained previously, if a source of sound waves emits waves at a lower frequency than expected, the source must be moving away from the observer. Similarly, if a star is emitting light waves at a lower frequency than expected—that is, if a star is exhibiting redshift—it must be moving away from observers on Earth.

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STEMscopedia: SOUND AND LIGHT WAVES What Do You Know? Career Corner: Acoustical Engineering Acoustical engineers apply their understanding of the physics of sound (acoustics) to minimize or maximize the behavior of sound waves. They may apply this understanding to the construction of a recording studio or concert hall. For example, in a recording studio, sound waves may reflect from the walls of the room, creating an unwanted reverberation. An acoustical engineer may cover the walls in a specialized foam padding to absorb some of the sound wave energy so that it does not reverberate as much in recordings. Similarly, an acoustical engineer may want to enhance the behavior of sound waves in a large, outdoor music pavilion. For example, sound waves may refract in unwanted ways if they travel from a colder region to a warmer region in the pavilion, causing “dead zones” where no music can be heard. An acoustical engineer may want to position speakers and audience seats to account for this behavior so that no audience seats will be located in dead zones. Furthermore, sound waves will diffract and decrease in quality as they travel around barriers between the sound source and audience members. As a result, an engineer may want to design a stadium seating venue so sound will not diffract through many audience members before reaching listeners in the back.

frequency: the number of times a wave cycles (or vibrates) in a given unit of time

Light Waves Light waves reflect from surfaces in different ways. For example, mirrors reflect all the light that strikes them. However, light behaves differently on other surfaces. For example, opaque surfaces do not allow light to pass through them. Light striking an opaque surface is either absorbed by the surface or reflected from it. Some objects absorb certain frequencies (colors) of light and reflect other frequencies. The particular frequencies of light that an object reflects determine the color of the object. For example, grass absorbs all frequencies of light except for green. That is, grass reflects green light. This is why grass appears green. White objects reflect most of the light striking them, while black objects absorb most of the light.

Connecting With Your Child Testing Hooke’s Law For this experiment, you will need a spring scale, a meter stick or tape measure, and several elastic objects, such as a coil spring, a rubber band, a bungee cord, and an archery bow. A calculator will also be useful.

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STEMscopedia: SOUND AND LIGHT WAVES According to Hooke’s law, for an elastic object such as a spring or rubber band, F=–kx. In this equation, x is the distance the object has been stretched or compressed from its resting point, and F is the force acting to restore the object to its resting point. The symbol k is a constant. This means the ratio of force to displacement (F/x) is always the same. To test this law for an elastic object, attach the hook of a spring scale to one end of the object, such as a rubber band, and stretch the band to various lengths. Record the force, as indicated by the spring scale, and the increase in the object’s length. Then calculate the ratio of force to displacement (F/x) for several stretched lengths. Is the result the same for each length? (It should be.) This confirms Hooke’s law. Repeat the experiment with the other elastic objects you have found. Here are some questions to discuss with your child: 1. Which do waves transfer from place to place: matter, energy, or both? 2. What is the frequency of a sound wave with a wavelength of two meters traveling at 340 meters per second? 3. A bungee jumper with a weight of 600 newtons dives off a tower. When he reaches the point where the elasticity of the bungee cord makes him spring back up, the bungee cord has increased its length by 10 meters. 4. What is the Hooke’s constant for the bungee cord? 5. A person hears a sound with a frequency of 100 hertz. How often does a crest of the sound 6. wave enter the listener’s ear?

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PS9DE Sound and Light Waves

Reading Science Name:

Date:

Group:

Doppler Effect and the Universe 1

In 1842, Christian Doppler proposed that there is a change in frequency of a wave, depending on the motion of the observer relative to the source of the wave. The observed frequency is higher than the emitted frequency when the source is moving toward the observer. The observed frequency is equal to the emitted frequency at the instant of passing by, and the observed frequency is lower than the emitted frequency when the source is moving away from the observer.

We are most familiar with the Doppler effect as it relates to sound. As a police car approaches, the sound waves generated by its siren are compressed. The waves reach your ears with higher frequency, and you hear them as higher pitched. Once the police car passes, the sound waves reaching your ear are stretched apart, reaching your ear with lower frequency. You hear the sound as being lower pitched. As frequency and wavelength have an inverse relationship, higher frequency sound has a shorter wavelength, while lower frequency sound has a longer wavelength. Velocity of the sound wave depends on the medium, so it is not affected by the relative motion of source and observer. The loudness of the siren, or amplitude of the wave, depends on the amount of energy the siren has.

Light waves behave similarly, but sensitive instruments are required to detect the shifts in wavelength. Telescopes, such as the Hubble Space Telescope in orbit, detect light from stars and galaxies. If a star is approaching Earth, its light will be shifted toward higher frequency blue light. This phenomenon is known as blueshift. On the other hand, if a star is moving farther away from Earth, the light coming from it will be shifted toward lower frequency. Since red light has the lowest frequency in the visible spectrum, the light will be redshifted.

Telescopes in space have several advantages over telescopes on Earth. Earth’s atmosphere absorbs much of the infrared and ultraviolet light, making it impossible for Earth-mounted telescopes to use these frequencies to study stars and planets. Furthermore, atmospheric turbulence limits the sharpness of images. The disadvantage of space telescopes is that they are very difficult to upgrade and repair.

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PS9DE Sound and Light Waves

Reading Science 5

Astronomers studying the dimensions of the universe use the shift in frequency to determine the direction of motion of stars and galaxies relative to Earth. All galaxies seen from Earth display a redshift, meaning that they are moving away from us. Moreover, galaxies located farther from Earth have a stronger redshift. The farther a galaxy is from us, the faster it is moving away from us.

Studying the light coming from stars shows that the universe is expanding. The rate of expansion appears to be increasing with time. Whether the universe will continue to expand indefinitely or reverse direction and contract again is not clear at this time. What is clear is that no one alive today will have to worry about being part of the next Big Bang, if there is one!

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PS9DE Sound and Light Waves

Reading Science 1.

The Doppler shift can be defined as a change in _____________ of a wave depending on the relative motion of wave source and receiver. A.

amplitude

frequency

quality

energy

A siren in the middle of town warns of an approaching tornado. You are in a car traveling directly away from the siren toward your house. How is the sound you hear while in the car different from what a person hears standing right next to the siren? A.

You hear a lower pitched sound.

You hear a higher pitched sound.

You hear the same pitch.

You hear a louder sound.

Most people have experienced the Doppler shift and sound waves, but humans don’t have direct experience with the Doppler shift and light waves. Why? A.

Only light from stars is subject to the Doppler shift.

Earth’s atmosphere blocks the Doppler shift.

The Doppler shift is too large for humans to perceive.

The human nervous system is not sensitive enough to detect the Doppler shift in light waves.

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PS9DE Sound and Light Waves

Reading Science 4.

Proxima Centauri is one of the stars nearest Earth. Its light is redshifted; therefore, it is _____________. A.

moving away from Earth

moving toward Earth

moving parallel to Earth

stationary with respect to Earth

While Proxima Centauri is relatively close to Earth, Procyon A is farther away. Which star’s light has a larger redshift? A.

Procyon A

Proxima Centauri

Neither. Their redshifts will be the same.

Not enough information is provided to answer the question.

What are the advantages of telescopes in space as opposed to telescopes on Earth? A.

They are easier to repair.

They can be bigger.

They can detect unimpeded infrared and ultraviolet light.

They are sturdier.

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PS9DE Sound and Light Waves

Math Connections Name:

Date:

Group:

Light Waves Through Various Media The speed of light, c, is 299,792,458 meters per second (m/s). However, it is approximated at 3.00 x 108 m/s. The data table below shows the speed of light waves through different media. Calculate the speed of light through each medium. Speed of Light

Medium

Calculation (m/s)

Vacuum

3.00 x 108

c / 1.0003

Air

c / 1.33

Water

c / 1.52

Glass

c / 1.64

Asphalt

c / 2.6

Lead

How does the speed of light change as it moves down the table through the various media?

What media does light travel through the fastest?

What media does light travel through the slowest?

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PS9DE Sound and Light Waves

Writing Science Name:

Date:

LOOK

THINK The Doppler Effect explains how certain sound waves seem to change relative to a listener’s location and the distance away from the source. When an object such as a siren gets closer to an inanimate object, the sound waves appear to drastically increase. Conversely, when the siren gets farther away, the sound waves appear to drastically decrease. WRITE When designing a siren for a police car, developers must take certain factors into consideration in regard to the Doppler Effect. Explain how the Doppler Effect, as seen through different media, translates into the designs used by such developers.

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PS9DE Sound and Light Waves

Writing Science Topic:

430

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Physical Science

PS10AB

Electricity and Circuits

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PS10AB Electricity and Circuits

Student Handout Name:

Date:

Take two wires, one battery, and one light bulb. Using the wires, hook everything up so the light bulb is lit. What is the voltage on the battery?

Disconnect the light bulb. This time, hook up three wires, two light bulbs, and one battery so that both light bulbs are lit. What is different from the first circuit you built?

Disconnect everything. This time, hook up three wires, two batteries, and one light bulb so that the light bulb is lit. What is different between the first and second circuits?

Why did the light bulb get dimmer in the second circuit?

Why did the light bulb get brighter in the third circuit?

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PS10AB Electricity and Circuits

Student Journal Name:

Date:

Group:

Part I: Ohm’s Law 1.

What are the three equations for Ohm’s law?

If the resistance is not changed but the voltage is increased, what happens to the current?

If the resistance is not changed but the voltage is decreased, what happens to the current?

If the voltage is not changed but the resistance is increased, what happens to the current?

If the voltage is not changed but the resistance is decreased, what happens to the current?

What is the general relationship between current and voltage?

What is the general relationship between current and resistance?

What is the current produced with a nine volt battery through a resistance of 100 ohms?

Find the current when a 12-volt battery is connected through a resistance of 25 ohms.

10. What voltage produces a current of 50 amps with a resistance of 20 ohms?

11. What voltage produces a current of 500 amps with a resistance of 50 ohms?

12. What resistance would produce a current of 200 amps with a potential difference of 2,000 volts?

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PS10AB Electricity and Circuits

Student Journal Part II: Circuits 1.

What do the blue dots represent?

When the light bulb is on, how do the blue dots behave?

When the voltage is doubled, what happens to the brightness of the bulb and the behavior of the blue dots?

When the source is changed to AC, what happens to the behavior of the blue dots?

AC stands for alternating current, and DC stands for direct current. Explain why these terms are used to describe electricity.

When the AC voltage is increased, what happens to the brightness of the bulb and the behavior of the blue dots?

For your I circuit, draw a diagram of what you have built. Catalogue the behavior of the dots when the switch is off and on.

For your II circuit, draw a diagram of what you have built. Catalogue the behavior of the dots when the switch is off and on.

For your III circuit, draw a diagram of what you have built. Catalogue the behavior of the dots when the switch is off and on.

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Student Journal

PS10AB Electricity and Circuits

Part II: Circuits, continued 10. What is a series circuit? What is a parallel circuit?

11. Which circuit—I, II, or III—represents a series circuit? Note that there may be more than one correct answer.

12. Which circuit—I, II, or III—represents a parallel circuit? Note that there may be more than one correct answer.

Analysis 1.

Why did the bulb get brighter when the voltage was increased?

What distinguishes AC electricity from DC electricity?

List two characteristics of a parallel circuit when compared to a series circuit:

Which is wired in series, christmas lights or a car?

Why is your house wired in parallel?

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STEMscopedia: ELECTRICTY AND CIRCUITS PS10AB

Reflect Think about things you might use in your daily life that contain electrical circuits. This list can get long very quickly because circuits are everywhere around us. Circuits light lamps, cook food, open automatic doors, and send and receive calls on mobile phones. The circuits used in many devices are very complicated, but we can break them down into simple parts. Knowing a little about circuits can help you every day. What is a circuit? How can we describe and use circuits? Conductors and Insulators Electric current is a flow of electrons—negatively charged particles—through an object or a substance. You can think of a circuit as a closed track along which current can flow. Some materials allow current to flow more easily than others. Materials called conductors allow current to flow easily. Materials called insulators do not allow easy current flow.

Most power lines are made from metal conductors such What gives a conductor its properties? In conductors, the atoms in as aluminum and steel. the material have loosely attached valence electrons. These electrons can move or drift easily between the atoms. Because electrons can flow easily through these materials, electric current flows easily. We say that the material conducts electricity. Metal objects such as tin, aluminum, copper, and brass are especially good conductors. Because of this, common circuits are made of copper wire. Gold and silver are even better conductors, but copper, aluminum, and steel are more abundant and cost effective. Power lines are made from metals such as aluminum and steel. What makes a good insulator? The atoms that make up an insulating material have tightly bound electrons. The electrons do not move easily from one atom to another or between atoms. Thus, little or no current flows in an insulator because electrons do not move easily between the atoms. Rubber, plastic, glass, and wood are some examples of insulators. Rubber insulators surround most electrical wires. These insulators keep us from getting shocked when we touch the wires.

Electrical cords are surrounded by rubber insulating material. This protects us from the current-conducting wires inside the rubber.

Take another look at the photograph of power lines on the previous page. Metal towers support the metal wires, which conduct strong electric currents. Yet if you were to touch the bottom of the metal tower, you would not get shocked. This is because an electrical insulator—usually ceramic— separates the wires from the tower.

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STEMscopedia: ELECTRICTY AND CIRCUITS Look Out Most houses have insulation in the walls and ceiling, and winter coats also have insulation. This insulation—known as thermal insulation because it helps to trap heat—is not the same as electrical insulation. However, many electrical insulators are also good thermal insulators. For example, a plastic spoon will not conduct electricity. It also will not heat up very much if you place it into a hot liquid. Thus, it is a good electrical insulator and a good thermal insulator. In general, though, electrical insulation and conduction are not the same as thermal insulation and conduction. In a simple circuit, wires connect a battery, switch, and light bulb. When the switch is open, there is a break in the circuit. No current flows, and the light bulb does not light. When the switch is closed, the circuit is connected, current flows, and the light bulb shines. Current Flow and Circuits A circuit provides a path for current, a flow of electric charge. In most solid conductors, such as metal wire, current is the flow of moving electrons through the material. The flow of electric current is measured in units of amperes (A). A key property of a circuit is that it must always be a closed loop. The reason for this is conservation of electric charge. The total number of charges in a circuit remains constant. In other words, electrons do not just appear and disappear in a circuit. If current flows in a circuit, the electrons must travel on a loop so the total number of electrons stays constant. Similarly, if there is a break in a circuit, current will not flow. This is how switches in electrical circuits work. For example, when a light switch is turned off, the switch causes a break in the light bulb circuit. When the switch is turned on, the path is connected and current flows to the light bulb. potential difference: the amount of energy needed to move a charged particle from one point to another in an electrical field Electric Potential Difference What causes current to flow? Electric current flows in a circuit when there is a potential difference between points in the circuit. A difference in electric potential means that charged particles gain or lose kinetic energy moving between points. A potential difference in a circuit is also called a voltage. Voltage is measured in units of volts (V). You can think of potential difference, or voltage, in the same way that you think of gravitational potential energy. For example, when a skier is at the bottom of a hill, she has zero gravitational potential energy. A ski lift takes her to the top of the hill, where she gains potential energy. The difference between her potential energy at the bottom and at the top can be thought of as a potential difference. Because the skier has potential energy at the top, she begins to slide down the hill toward the bottom. As she moves, her potential energy is converted into kinetic energy.

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STEMscopedia: ELECTRICTY AND CIRCUITS The motion of the skier as she slides down the hill is similar to the motion of an electron as it moves from high to low electrical potential energy in a circuit. In other words, the flow of current is like the skier moving down a hill. When the electron has flowed from one side of a circuit to the other, it must encounter a source of energy that “lifts it back up” to a higher potential energy again so that it can flow back along the circuit. This is what all sources of voltage, such as batteries, do in circuits. (The comparison to the skier is not perfect. Electrons do not fall to lower elevations as they move along a wire nor do they rise to higher elevations when they pass through a battery. The electrons simply gain enough energy to make another trip around the circuit, just as the skier—by moving to the top of the hill—gains enough energy to slide back down.) Everyday Life: Batteries and Voltage A battery provides a potential difference in a circuit. Inside a battery, chemical reactions take place that separate positive and negative charges. Positive charges (protons) are moved to the positive terminal (end) of the battery. Similarly, negative charges (electrons) are moved to the negative terminal (end). Because positive and negative charges are attracted to one another, the battery must contain materials that make it difficult for the electrons to move back to the protons. This creates a potential difference, or voltage, between the charges. The voltage rating of a battery, such as 9 volts or 1.5 volts, indicates the size of the potential difference.

Batteries produce a potential difference that allows current to flow around a circuit. One AA battery provides 1.5 volts.

When wire is connected between the two terminals, electrons at the negative terminal are attracted to the protons at the positive terminal. Thus, electrons flow around the closed path from one terminal to the other. Eventually, the chemical energy that separates positive and negative charges in the battery runs out. The battery no longer produces voltage and no current will flow around a circuit. When this happens, we say that the battery is dead.

Ohm’s Law Voltage makes current flow. How much current flows in a circuit with a voltage source? The German physicist Georg Ohm discovered that the current in many materials is proportional to the applied voltage. According to Ohm’s law: V = IR We can also write Ohm’s law as follows: I = V/R In these equations, V is the voltage of the circuit, I is the current flowing through the circuit, and R is the resistance of the circuit. Resistance is a measurement of how much a conducting material resists the flow of current through it. Resistance is measured in ohms, written with the symbol Ω (the Greek letter omega). As previously discussed, voltage is measured in volts (V), and current is measured in amperes (A). You may wonder why current is assigned the variable I in Ohm’s law. The answer is that Ohm’s law refers to current intensity.

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STEMscopedia: ELECTRICTY AND CIRCUITS Resistance indicates how easily current can flow in a circuit. A large resistance means current has a harder time flowing. Increasing the resistance in a circuit leads to less current. If the resistance decreases, the current increases. Ohm studied the electrical properties of many different materials. Ohm’s law states that for many materials, the resistance is constant over a wide range of voltages. For these materials, a graph of applied voltage versus the current shows a straight line. Resistors that stay constant over a wide range of voltages are called Ohmic resistors. For example, if a 60-Ω Ohmic resistor is wired Typical resistors have color into a circuit, we can increase the voltage through the circuit and the markings that indicate their current will decrease, but the resistance will always stay the same. resistance. Not all resistors are Ohmic. Materials that do not obey Ohm’s law are said to be non-Ohmic. In a non-Ohmic material or device, the graph of applied voltage versus current does not look like a straight line. The material does not have a fixed value of resistance. In these cases, you cannot use Ohm’s law to relate voltage, current, and resistance. Non-Ohmic devices include LEDs, like those in many television and computer screens. Circuit Power Electrons flow out of a voltage source, through the rest of the circuit, and back into the voltage source. Conservation of energy means that electrons must lose the energy they gain from the voltage before returning to the voltage source. Where does this energy go? The electrons lose this energy in the rest of the circuit. For instance, in light bulbs, energy from a voltage source turns into light and heat. The electrons moving in a circuit carry energy from one part of a circuit to another. Power is defined as the change in energy over time in a system. Electrical power is the rate at which energy moves through a circuit. The moving current in a circuit provides power that we can use in many devices. This power can appear as light, heat, or mechanical power, like in an automatic door. Power is measured in units of watts (W). Power in an electric circuit is a function of current (I) and voltage (V): P = IV

What Do You Think? A light bulb has a resistance of 240 Ω. It is connected to a home electrical outlet, which supplies 120 volts. What is the current in the circuit? How much power does the resistor produce? What do you think happens to the lost energy?

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STEMscopedia: ELECTRICTY AND CIRCUITS Series Circuits Common devices have complicated circuits inside them. We can break many circuits down, though, into two basic types: series and parallel. In a series circuit, current can flow along a single path only. In a parallel circuit, current can flow along two or more paths between two points. To discuss series circuits, we must understand what circuits are made of. All circuits have a voltage source, such as a battery, and some In a series circuit, resistors conducting material, such as a wire. They must also have a circuit are wired one after the element (or many circuit elements) to which power is delivered. A typical other along a single path. circuit element is a resistor, but there are other types of elements, such This circuit contains an as capacitors and inductors. A series circuit may have several circuit elements in it, but the elements connect one after another along a single open switch. Electricity will path. That is, the current must flow through each element, one after the not flow through the circuit until the switch is closed. other, in a series circuit. As we discussed earlier, electrons lose energy as they move from the beginning to the end of the circuit loop. We call this a voltage drop. We can use an instrument known as a voltmeter to measure the voltage drop through different locations in a circuit. For example, if one end of the voltmeter is placed on the positive terminal of a battery and the other end is placed on the negative terminal, a voltmeter should show a voltage drop equal to the total voltage of the battery. However, there will be a voltage drop as electrons move across each circuit element in the circuit. In a series circuit, the sum of the voltage drop across each element in the circuit equals the total voltage in the circuit. This property is due to the conservation of energy. The total energy lost by electrons moving along the circuit must equal the energy lost along each step. For example, if there are two resistors in a circuit, R1 and R2, the voltage drop across each resistor is V1 and V2, respectively. If the total voltage in the circuit is V, then V = V1 + V2. While the voltage drops across different elements in a series circuit, the current flowing through each element is the same. The total current flowing through a series circuit, I, is equal to the sum of the current flowing through each resistor, I1 and I2, such that I = I1 + I2. When we think of the resistance of circuit elements in a circuit, we can think of many resistors combined to act like one big resistor. This idea is known as equivalent resistance. The equivalent resistance, Req, of resistors in a series circuit is the sum of the individual resistances: Req = R1 + R2. The total resistance increases as you connect more resistors in a series.

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STEMscopedia: ELECTRICTY AND CIRCUITS To solve problems in series circuits, it may be helpful to follow these steps: 1. Calculate the equivalent resistance, Req, of the circuit. This is the sum of each resistor in the circuit. 2. Use Ohm’s law to determine the total current in the circuit. The current, I, in the circuit is equal to the voltage, V, of the voltage source divided by the equivalent resistance, Req, of the series resistors: I = V/Req. 3. Apply Ohm’s law to each individual resistor to determine the voltage drop across it. For a circuit with resistors R1 and R2, the voltage drop across each is as follows: V1 = I1R1 and V2 =I2R2. (Remember, I = I1 = I2 and V = V1 + V2)

What Do You Think? • • •

By Ohm’s law, current equals voltage divided by resistance. Therefore, 120 V ÷ 240 Ω = 0.5 A. Power (measured in watts) equals current (in amperes) multiplied by voltage (in volts). Therefore, 0.5 A × 120 V = 60 W. The electrical energy is transformed into light and thermal energy.

Parallel Circuits The other type of simple circuit is called a parallel circuit. In a parallel circuit, current can flow along multiple paths between two points. The two paths are said to be in parallel. What is the voltage across a parallel pair of resistors? Conservation of energy tells us the voltage changes by the same amount along each parallel path. Therefore, the voltage across parallel resistors is the same for each path and is equal to the applied voltage from a battery or other source. For example, in a parallel circuit with two resistors, the total voltage in the circuit, V, is equal to the voltage drop across each resistor, V1 and V2, such that: V = V1 = V2.

When circuit elements are wired in parallel, current can flow along various paths as it travels around the circuit.

Recall that the current through a series circuit is the same through all resistors. In a parallel circuit, however, the current flowing into the parallel resistors divides like a river into two smaller currents. In this case, the total current in the circuit, I, is equal to the sum of the current through each branch of the circuit: I = I1 + I2. Equivalent resistance in parallel circuits is also different than in series circuits. Consider again a parallel circuit with two resistors. While the equivalent resistance of a series circuit is the sum of each resistor, the equivalent resistance of a parallel circuit is calculated in the following way:

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Adding more resistors to a parallel circuit decreases the equivalent resistance of those branches.

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STEMscopedia: ELECTRICTY AND CIRCUITS

In this case, the reciprocal of the equivalent resistance equals the sum of the reciprocals of all resistances. You can confirm this using the equation above. Consider a parallel circuit containing two 4-Ω resistors:

For parallel circuits, adding more resistors on more branches will decrease the equivalent resistance of those resistors. This is similar to how opening a new lane on a highway will decrease the congestion on the road. To solve problems in parallel circuits, it may be helpful to follow these steps: 1. Calculate the equivalent resistance, Req, of the circuit using the reciprocal relationship:

2. Use Ohm’s law to determine the total current in the circuit. The current, I, in the circuit is equal to the voltage, V, of the voltage source divided by the equivalent resistance, Req, of the series resistors: I = V/Req. 3. Apply Ohm’s law to each individual resistor to determine the voltage drop across it. For a circuit with resistors R1 and R2, the voltage drop across each is as follows: V1 = I1R1 and V2 =I2R2. (Remember, V = V1 = V2 and I = I1 + I2.)

Look Out If current travels along a path, does electricity move in a certain direction? In fact, it does. You can observe this by experimenting with a small, battery-operated fan. When the battery faces one direction, the fan spins clockwise. When the battery faces the opposite direction, the fan spins counterclockwise. The fan changes direction because the flow of current through the circuit has changed direction.

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STEMscopedia: ELECTRICTY AND CIRCUITS What Do You Know? Practice designing circuits. For each example below, draw a simple circuit that has the correct properties. Assume that each circuit includes one voltage source and resistors. You may need to use Ohm’s law, as well as your knowledge of series and parallel circuits, to determine the resistance of a resistor. Label the voltage source and resistance of each resistor in the circuits. 1. Circuit with a 9.0 volt battery and a total current of 4.5 amperes 2. Circuit with a total current of 0.75 amperes and a 12 Ω resistor 3. Parallel circuit with a battery and two resistors • One resistor is 12 Ω and the other is 6 Ω. • The current through the circuit is 1.5 amperes.

Connecting With Your Child Build Your Own Circuit Help your child design and build circuits. A simple circuit kit could include standard household batteries for voltage sources and a string of holiday lights or small LEDs for resistors. If using a string of lights, use wire cutters to cut the string into individual bulbs or short segments of bulbs. You may need to strip back some of the plastic insulation to expose the wires. You may wish to use tape to connect the wires and batteries. Guide your child in putting together different combinations of bulbs and batteries and observing the relative brightness of the lights. Make sure your child understands what the brightness signifies. (The brightness of a bulb is related to the power output of the bulb, which is defined as P = I(∆V). According to Ohm’s law, adding more resistors to a series circuit will decrease the total current through each bulb. This will decrease the brightness of the bulbs. However, adding more resistors to a parallel circuit will increase the total current through each bulb. This will increase the brightness of the bulbs.) Have your child design a few combinations, then predict the relative brightness of the combinations. Your child should then check and compare the results with his or her predictions. Here are some questions to discuss with your child: 1. For a fixed voltage, how can we make a brighter combination of lights? 2. How can we predict the brightness of a combination? 3. How can we make a more accurate prediction of the combination?

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PS10AB Electricity and Circuits

Reading Science Name:

Date:

Group:

Designing a Circuit in a Commercial Building 1

Thick smoke wafts through the office building. The fire alarm is flashing and blaring. This is your first day on the job. Where is the stairwell? You look up and see a red exit sign above one of the doors. As you emerge from the building coughing, you see your new boss and coworkers standing in the parking lot. Even though you were unfamiliar with the building, you found your way to safety. Thanks to an entire team of engineers and craftsmen, the exit signs led you in the right direction.

Most internally illuminated exit signs today use LED lamps. One major advantage of LEDs is the lifespan of the light. LEDs last 50,000–200,000 hours, while incandescent bulbs last only about 1,000–2,000 hours. A longer lifespan means that the lamps must be replaced less often, saving in both material and labor cost. In addition, for the same brightness, LEDs consume 2–5 watts of power versus 30 watts for incandescent lamps. Lower wattage translates to less energy used, which is better for the environment and cheaper to operate over the lifespan of the building.

Most commercial buildings receive their electrical supply from a utility company at 480 and 277 volts AC. Each electrical circuit in the building is protected by 20 amp circuit breakers. Electrical codes limit the load on each circuit to 80% of the circuit breaker rating, which is 4,432 watts for each circuit. Since each LED exit sign draws around 5 watts of power, an engineer could design about 800 exit signs on each circuit! In practice, all the exit signs on one floor are usually connected to a single circuit. Sometimes hallway lights are also connected to the same circuit. Since these lights are switched on and off, and exit signs are not, the exit signs are connected to a part of the circuit that is not switched.

What happens if the power goes out? Do exit signs stay illuminated if the power from the utility company to the building is interrupted? Absolutely, yes! To ensure that exit signs remain illuminated in the absence of utility power, one of two design approaches is chosen. If the building has an emergency generator, exit signs are connected to an electrical circuit served by the generator. Another option is to install exit signs that have batteries for backup power. The disadvantage of the second option is that the batteries require testing, maintenance, and replacement at regular intervals. Since paying someone to test, maintain, and replace the batteries is expensive, exit signs are usually connected to the emergency generator when available.

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PS10AB Electricity and Circuits

Reading Science 5

Electrical engineers design circuits every day. They have to consider electrical theory, taking into account voltage, current, size of the conductor, and circuit breaker, as well as other, more advanced factors. In addition, engineers must be aware of the practical and financial consequences of their design choices. They attempt to minimize construction and maintenance costs, while meeting all applicable codes and regulations. For example, the exit signs can be connected directly to a 277 volt circuit, a practice that eliminates the need for a transformer. Transformers take one voltage and change it to another. They can be expensive. Next time you look up in a room and see lights or walk down a corridor and see the exit sign above a door, remember that engineering design combined with an electrician’s skill made it all possible!

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PS10AB Electricity and Circuits

Reading Science 1.

Which of the following statements correctly describes one advantage of LEDs over incandescent light bulbs? A.

LEDs have a longer lifespan.

LEDs use more watts for the same illumination.

LEDs can be replaced remotely.

LEDs are harder to purchase.

Commercial buildings receive power from the utility company at ______________. A.

120 and 208 volts AC

120 and 408 volts AC

208 and 277 volts AC

277 and 408 volts AC

Exit signs ______________. A.

are switched on and off every day

have to stay illuminated even when utility power is lost

are never connected to a circuit with other lights

always have their own batteries

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PS10AB Electricity and Circuits

Reading Science 4.

According to the passage, which two pieces of equipment serve the same function? A.

Exit lights and emergency generators

Exit lights and hallway lights

Batteries and emergency generators

Exit lights and batteries

Installing exit lights that run on batteries into a building means that ______________. A.

technicians have to test, maintain, and replace the batteries regularly

building occupants have to report burned out lights immediately

the building requires a larger emergency generator than usual

the exit lights have to be placed closer together because they are not as bright

Electrical engineers are responsible for ______________. A.

running conduits and wires through the building

making sure building occupants have enough stairwells

designing the electrical circuits to applicable codes

hiring utility companies

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PS10AB Electricity and Circuits

Math Connections Name:

Date:

Group:

Electrical Circuits A series circuit is a type of circuit in which the electrical current runs through each component linearly, one after another, and each component handles the same current. A parallel circuit is a type of circuit in which the electrical current runs through multiple components simultaneously, and each component handles the same voltage. The relationship between current, voltage, and resistance in an electrical circuit is fundamental to the operation of any circuit or device and is expressed by Ohm’s Law (the voltage is equal to the product of the electrical current and the resistance against the current). The formula for Ohm’s Law is V = IR, where V is the voltage (volts, V), I is the current (amps), and R is the resistance (ohms, Ω). 1.

A 52-V battery powers a pair of 36-Ω resistors connected in series. What is the current flowing through the system? Round to the nearest tenth.

A 52-V battery powers a pair of 36-Ω resistors connected in parallel. What is the current flowing through the system?

Compare the answers to questions 1 and 2. Discuss the similarities and differences.

Given the diagram on the right,

Compare the brightness of each light bulb.

Which bulb draws the most current?

If bulb B is unscrewed, what would happen to the other two bulbs?

If bulb A is unscrewed, what would happen to the other two bulbs?

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PS10AB Electricity and Circuits

Math Connections 5.

Look at the diagram of a combination of series and parallel resistors in a circuit. a)

What is the parallel part of the circuit?

How could the parallel part of the circuit be replaced without changing the total current from the battery?

Resistance is a measurement of how an object or medium opposes the flow of electric current. A resistor is an electrical component that provides electrical resistance in a circuit. •

Total Resistance in Series Circuits: In a series circuit, the voltages of the components are added together to get the total voltage in the circuit. Therefore, the total resistance is the sum of the resistances of the components. R total = R1 + R2 + R3 +….. +Rn

•

Total Resistance in Parallel Circuits: In a parallel circuit, the currents of the components are added together to get the total current in the circuit. Therefore, reciprocal of the total resistance is the sum of the reciprocals of the resistances of the components. 1/R total = 1/R1 + 1/R2 + 1/R3 +….. + 1/Rn

Given the circuit below, what is the current in the battery? Hint: What is needed before calculating the current?

A heating pad has several strips of heater wire connected in parallel. Consider eight of the wires, each with 4 Ω resistance, connected to a 12 V power source. Given this scenario, answer the following: a)

What is the total resistance of the eight wires? (Wires are in two groups of 2)

What is the total current?

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PS10AB Electricity and Circuits

Writing Science Name:

Date:

LOOK

THINK Circuits connected in parallel behave differently from circuits connected in series. Strings of lights are used by many people around holidays. Christmas lights are available colored, clear, twinkling, etc. For Halloween, some people use orange lights, or ones with covers shaped like bats or pumpkins. Have you seen the ones that look like red chili peppers? Each string of light has the same parts. A connector plug at one end, followed by one or more lights. Often the string has a connector at the other end, allowing strings to be connected together. But, the outside appearance does not tell you how the lights are actually connected in a circuit. The diagram above shows a single strand of lights with three light bulbs. In addition to the circuit drawn above, you also have access to a multimeter and can apply it to the circuit at the positions indicated by numbers 1-4 on the diagram. WRITE Describe the behavior of the circuit when all bulbs are working and when one is removed. Be sure to • clearly state your central idea; • organize your thoughts; • develop your essay in detail; • choose your words carefully; and • use correct spelling, capitalization, punctuation, and grammar. © Accelerate Learning Inc. - All Rights Reserved

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PS10AB Electricity and Circuits

Writing Science Topic:

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Physical Science

PS10C

Magnetism and Electricity

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455

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PS10C Magnetism and Electricity

Student Handout Name:

Date:

Currents and Magnetism Permanent or Not? Sort the cards given to you by your teacher into two categories: Permanent (always magnetic) and Nonpermanent (can turn the magnetism on and off). Once your group has sorted the cards, complete the table below. Permanent

Nonpermanent

Reflection Questions 1.

List some advantages of using permanent magnets over nonpermanent magnets

List some advantages of using nonpermanent magnets over permanent magnets.

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PS10C Magnetism and Electricity

Student Journal Name:

Date:

Group:

Background 1.

What is a current?

What is a magnetic field?

Explain how magnetism and electricity are related.

Describe how an electromagnet works.

Part I: Magnetism From Electric Current 1.

Describe what happened to the compass when you touched the free end of the wire to the other end of the battery in step 3.

Describe what happened to the compass when you switched the end of the battery in step 4.

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PS10C Magnetism and Electricity

Student Journal Part I: Magnetism From Electric Current, continued 3.

What is the relationship between the direction of the battery and the direction of the compass needle?

Part II: Make an Electromagnet 1.

Describe what happens when you touch the nail to the paper clip while both ends of the wire are connected to the battery.

Describe what happens to the paper clip when you disconnect the wire from one end of the battery.

How is an electromagnet different from a permanent magnet?

How do you think an electromagnet could be more useful than a permanent magnet?

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PS10C Magnetism and Electricity

Student Journal Part III: Electromagnet Investigation 1.

What variable will you change?

_______________________________________________________________________________ 2.

How will you measure your results?

_______________________________________________________________________________ 3.

What materials will you need?

What steps will you take to carry out your investigation? (Make a detailed list that includes such things as how to build your electromagnet, how you will change your variable, and how to measure your results.)

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PS10C Magnetism and Electricity

Student Journal Part III: Electromagnet Investigation, continued 5.

Set up your data table and carry out your investigation. Variable

# of Paper Clips Picked Up

Which change in your variable resulted in the most paper clips picked up?

_______________________________________________________________________________ 7.

Were you able to make your electromagnet stronger? ________________________________

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PS10C Magnetism and Electricity

Student Journal Part III: Electromagnet Investigation, continued 8.

Write a conclusion paragraph about your experiment. This conclusion should include what you were testing, how you were able to make your electromagnet stronger, and any changes you would make next time.

Discuss your results with groups that tested different variables. What are three ways to make a stronger electromagnet?

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STEMscopedia: MAGNETISM AND ELECTRICITY PS10C

Reflect Have you ever used a cell phone, computer, or microwave oven? If you have, then you have used a device that employs both magnetic and electric forces. Every computer contains magnets for data storage and to display images on computer screens. Magnets are inside the speakers of computers and cell phones. Inside of a microwave is a microwave generator called a magnetron. The magnetron transforms electrical energy into high-powered radio waves. The magnetron blasts these waves at the food inside the microwave. The microwaves bounce back and forth as they penetrate inside the food. They make the Mobile devices, computers, and microwaves all use molecules inside the food vibrate more quickly, producing heat. magnetic and electric forces. Magnetic and electric forces are two forces that occur in nature. Magnetic and electric forces are closely related because both are caused by negative and positive changes in matter. Atoms contain a positively charged nucleus and a negatively charged cloud of electrons. Both electric and magnetic forces are produced when charges from one piece of matter interact with those of another piece of matter. These forces can be attractive (pulling objects together) or repulsive (pushing objects apart). Magnetism, or magnetic force, is a noncontact force exerted by a magnet. A magnet is any material that attracts iron, a metallic element, and a few other metals. A magnetic force exists between a magnet and the object that is attracted to it. The magnetic force is exerted over a distance and includes forces of attraction and repulsion. A magnet can exert a force over a distance because the magnet is surrounded by a magnetic field. Magnetic force and its resultant magnetic field have a direction. You can see the magnetic field surrounding a bar magnet A magnet is surrounded by in the picture to the right. The pattern of iron filings shows the lines of a magnetic field. force that make up the magnetic field of the magnet. The concentrations of filings near the magnet’s poles indicate areas of strongest force. Magnetic field lines never cross. Electric forces are forces that occur due to electric charges. There are two types of electric charges: positive and negative. An electric charge is described by the electric field associated with it. An electric field is produced by all electric charges, whether they are moving or stationary. An electric field can also be produced using varying magnetic fields. Electric forces can be either attractive (if both charges are of different types) or repulsive (if both charges are of the same type).

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Electric field lines point toward a negative charge.

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STEMscopedia: MAGNETISM AND ELECTRICITY

Look Out Electric force is an invisible force produced by an electrically charged particle. Objects can have electric charges. Most objects have equal charges. However, if a positive charge builds up, the object becomes positive. If a negative charge builds up, the object becomes negative. Charged particles or objects with more electric charge produce a stronger and larger electric force. The strength of the electric force decreases with distance. Electric field lines can be drawn around and between negative charges to show an electric field. The electric field has a direction because electric forces have direction. The electric force is directed away from a positive charge and toward a negative charge. To illustrate this, electric field lines are drawn with arrows that point toward a negative charge and away from a positive charge. Energy contained within an electric field is called electricity. Electric energy can build up on an object (static electricity) or move from place to place (current electricity). Earth behaves like a giant magnet. At Earth’s center is a core of solid iron with an outer layer of molten, flowing iron. Earth’s core acts like a giant bar magnet that creates a magnetic field around Earth. This magnetic field extends outward and around Earth and down toward Earth’s core at its poles. Earth has two different types of poles: geographic and magnetic. You are probably familiar with Earth’s geographic north and south poles. These are imaginary points that identify Earth’s axis of rotation. Earth spins around the north and south geographic poles. The geographic poles are also where the lines of longitude converge. Geographic poles are different from magnetic poles. The magnetic poles are where Earth’s magnetic field extends downward toward the core. Earth’s magnetic field converges at the north and south poles. Earth’s magnetic poles are not located at the same position as the geographic poles. The magnetic poles are actually located about 10 degrees (965 kilometers) from Earth’s geographic poles. The magnetic poles change position over time due to changes in the flow of molten iron in Earth’s outer core. Called polar drift, Earth’s magnetic poles drift 55 to 60 kilometers every year. Earth is surrounded by a magnetic field.

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STEMscopedia: MAGNETISM AND ELECTRICITY

Complete the table to compare magnetic and electric forces. Property

Type of particle responsible

Magnetic Force

Electric Force

Produced by

Travels through

Direction of force

Common uses

An electromagnet is created by running an electric current through a wire. When the wire connected to a power source is coiled or wrapped around a magnetic object, the object becomes a magnet. Electricity causes the magnetic object to exert a magnetic force. The force is exerted only when current is flowing through the wire in a complete circuit. An electromagnet’s strength is dependent on two factors: the voltage supplied by the power source and the number of times the wire is coiled around the object. An electromagnet is easily controlled by turning the current “off” or “on.” Because of this, electromagnets have many practical uses.

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An electromagnet is a magnet created by an electric current.

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STEMscopedia: MAGNETISM AND ELECTRICITY

Connecting With Your Child Iron is an important element found in Earth’s core and in many materials and objects. Since iron is attracted to a magnet, you can analyze different objects to see which contains iron. Students will investigate the difference between a bar magnet and an electromagnet while attracting various materials.

Objects containing iron are attracted to a magnet. You will need the following materials: Materials Pencil • Magnets (marked “N” for north and “S” south to show how magnet repel) • 1 medium shoebox or bin (to put the materials below in) • 1 thin metal spoon or nail • 1 60 cm wire, insulated with ends stripped • 1 battery, C or D • 1 paper clip • 1 ruler • 1 Lego or plastic block • 1 nickel or coin • 1 nail • 1 scissors • 1 eraser • 1 pencil • Iron filings What To Do: 1. Gather materials and make the electromagnets. 2. To create an electromagnet using the nail or spoon, complete the following steps: Leave a few inches of the wire loose at one end of the metal object. Wrap the wire around the object tightly. (The more tightly you wrap the wire, the stronger the electromagnet will be.) Leave a few inches of wire at the other end of the object. Attach one end of the open wire to the top of a battery and secure with electrical tape. Attach the other end of the wire to the bottom of the battery and secure with electrical tape.

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STEMscopedia: MAGNETISM AND ELECTRICITY

3. Have students brainstorm a list of ways magnets are used in common everyday things (doorbells, phones, speakers, compasses, computers, microwaves, etc.). 4. Let students explore with the magnets and answer the following questions. 5. Discuss what surprised students about the magnetic experiments. 6. If you have magnets marked with north and south, have student play with those magnets and see that magnets attract and repel other magnets. Questions: 1. Compare and contrast a bar magnet and an electromagnet. 2.

Explain how you could “turn off” your electromagnet.

What happened when you put iron filings around the bar magnet? What happened when you put iron filings around the electromagnet? Explain the difference in direction of force between the two.

What type of electric current did you use to power your electromagnet?

Discuss which objects are magnetic and which objects were not magnetic.

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PS10C Magnetism and Electricity

Reading Science Name:

Date:

Solar Generators 1

Solar power generators use energy from the Sun to make electricity. Not to be confused with photoelectric panels, which change sunlight directly into current, but solar power generators use the Sun’s heat to produce electricity. One major advantage is that they produce power with the carbon dioxide emissions produced by coal and natural gas power plants. Solar power generators use electromagnetic induction to function. When you change a magnetic field by rotating magnets inside a coil, an electric current is produced.

Most power plants produce energy with fossil fuels that create steam to turn a turbine generator. A generator changes mechanical energy (turning turbine blades) into electrical energy and creates current. Wind farms use sets of three enormous fan blades attached to turbine generators. Wind moves the blades, and the turbine converts the energy of moving air to electricity.

Unfortunately, most power plants burn fossil fuels like coal to heat water and produce steam, which turns the turbine generator. However, solar thermal plants do not need fossil fuels because they use a series of outdoor mirror panels that collect and intensify the Sun’s rays to produce the necessary heat. This means no emissions are created by burning any fuel.

In order to heat water, solar thermal plants use solar collectors in fields with rows of large mirrors shaped like troughs. Pipes are laid on each line of collectors. The mirrors reflect the Sun’s energy to focus the heat onto the water pipes, which superheats the water to about 300º Celsius. Pipes carry the superheated water to the turbine, producing electricity.

A different type of solar plant uses a centralized tower of parabolic mirrors to collect and heat liquid. All the mirrors focus on the same point to create more steam to drive a larger turbine, ultimately creating more electricity. A central tower allows the use of alternative liquids such as molten salt, which keeps heat longer than water and can operate at night when other solar generators are not active.

Although they do not produce emissions, solar power plants still have an impact on the local environment. Solar power technology requires large areas of land. Renewable energy and the reduction of greenhouse gas emissions are important goals to maintain a healthy planet, but so is the conservation of wildlife and their delicate habitats. Solar power farms have pros and cons, and ongoing discussions are needed to find adequate solutions that properly balance environmental issues and the need for power production.

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PS10C Magnetism and Electricity

Reading Science 1.

What can solar photoelectric panels do that solar generators cannot do? A.

Capture sunlight

Produce energy

Produce steam

Change sunlight directly into electricity

Which of the following best describes how electromagnetic induction produces electric current? A.

A magnet rotating inside a metal coil

Steam rotating in a coil

Pipes carrying magnetism

Steam running through the center of a coil

What is the problem with most power plants? A.

Overuse of fossil fuels

Overuse of renewable energy sources

Overuse of steam

Overuse of molten salt

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PS10C Magnetism and Electricity

Reading Science 4.

Why are trough-shaped or parabolic mirrors sometimes used in solar generators? A.

They are cheaper than regular mirrors.

They are lightweight mirrors.

They can focus the Sun’s heat on a particular area.

They can focus steam on a particular area.

Why are environmentalists concerned about solar generator power plants? A.

These power plants will burn fossil fuels.

Solar generator power plants need lots of land, which impacts wildlife habitats.

Solar generators give off radiation.

Solar generators pollute the air and water.

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PS10C Magnetism and Electricity

Math Connections Name:

Date:

Group:

The magnetic field of a copper wire can be measured with the following formula: B = μI/2R, where B represents the magnetic field, μ is a constant equaling 4 πx10-7 Tesla-meters/amp, I is the current in amps and R is the radius of the wire. 1.

Determine what unit of measurement would be best to measure the radius of the wire. Justify your answer.

Show two ways to calculate the radius of the wire given the following information. B = 18.2 I = 27 amps

Compare and contrast the relationships between the radius and the magnetic field to the current and the magnetic field.

Write an equation to solve for each variable of the equation.

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PS10C Magnetism and Electricity

Math Connections Daniel is making a model of the solar system and he wants to include the magnetic fields of each planet on his model. He starts with a paper model shown below. He compares the actual radius of a planet and how far the magnetic field extends out to the radius of the model planet (in inches) in order to calculate how far the magnetic field should extend from the planet in the model. Measure the radius of each planet on the model (in inches) and use ratios to calculate the range of the magnetic field on the model. (Round to the third decimal place.)

SUN

Mercury Actual R

Magnetic Field

1,500 miles

3,000 miles

3,760 miles

150 miles

4,000 miles

40,000 miles

2,100 miles

450 miles

43,400 miles

4,300,000 miles

36,200 miles

23,200,000 miles

15,800 miles

7,300 miles

15,300 miles

8,400 miles

Venus Earth Mars

Jupiter

Saturn

Model R

Model’s Field

Uranus

Neptune

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PS10C Magnetism and Electricity

Writing Science Name:

Date:

LOOK

THINK Lightning is caused when electrons quickly move from one place to another. Because of its relationship with magnetism, electromagnetic pulses can occur. An electromagnetic pulse is described as a surge of electromagnetic energy in a powerful burst. Think about the experiments conducted in class to demonstrate the relationship between magnets and electricity. WRITE Explain the relationship between magnetism and the movement of electrical charges in a power surge caused by lightning, and the reasoning behind surge protectors.

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PS10C Magnetism and Electricity

Writing Science Topic:

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acceleration

GLOSSARY OF TERMS

balanced chemical reaction

acceleration – the rate of change in velocity; speeding up, slowing down, or changing direction

amplitude – the height of a wave measured from midway between the highest and lowest points

acidic solution – a solution in which the hydrogen concentration is greater than the hydroxide concentration

anion – any atom or group of atoms with a negative charge

action-reaction pair – for every action force, there is an equal and opposite reaction force alkali metals – any of the univalent elements belonging to Group 1A of the periodic table; shares similar properties

aqueous solution – a solution in which the solvent is water atom – the smallest particle of an element; made of electrons, protons, and neutrons atomic mass – the mass of an atom approximately equal to the number of protons and neutrons in the atom

alkaline earth metals – any of balanced chemical reaction the bivalent metals belonging to – a chemical equation in which mass is conserved and each Group 2A of the periodic table side of the equation has the same number of atoms of each alternative energy – any energy source other than from element fossil fuels

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basic solution

GLOSSARY OF TERMS

basic solution – a solution in which the hydroxide concentration is greater than the hydrogen concentration binary molecule – molecular compounds formed by two nonmetal elements, or by a metalloid and a nonmetal element

chemical nomenclature

chemical equation – a representation of a chemical reaction using numbers and symbols of the elements to represent atoms and molecules chemical formula – a shorthand notation that uses chemical symbols and numbers as subscripts to represent the type and number of atoms that are present in the smallest unit of the substance

boiling point – the temperature at which a substance changes states from chemical names – a liquid to a gas standardized names for cation – any atom or group of compounds that give the atoms with a positive charge chemical composition of the compound chemical energy – energy stored in the particles that chemical nomenclature make up food, fuel, and other – standardized names for matter, which is released during compounds that give the a chemical reaction such as chemical composition of the burning wood, or the reactions compound that occur in the cells of organisms

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chemical reaction

GLOSSARY OF TERMS

direction

chemical reaction – a process by which two or more chemical substances interact and are producing different chemical substances

convection – transfer of heat energy through the rising of hotter liquids and gases and the falling of cooler liquids and gases

coefficient – a number placed in front of a chemical symbol or formula in order to balance the equation

covalent compounds – a compound created when two (or more) atoms bond covalently, sharing electrons and creating a molecule

compound – a substance made of two or more elements that are chemically combined in fixed amounts

current – the flow of an electrical charge through an object or medium

condensation – the process by which a sample of matter changes from a gaseous state to a liquid state conduction – the transfer of energy from one medium to another through direct contact conductor – a substance that readily transfers heat or electrical energy

SSS GA18 SN Physical Science.indb 481

density – the amount of matter in a given space or volume; it is a relationship between mass and volume; less dense matter will form layers above dense matter. diffraction – occurs when a wave encounters an object in its path and bends around it direction – a straight path that something could move along 481

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dissolve

GLOSSARY OF TERMS

dissolve – to become incorporated into a liquid to form a solution distance-time graph – illustrates changes in motion; time is graphed on the x-axis and distance is graphed on the y-axis. Doppler effect – an apparent shift in the frequency of a wave due to the motion of the observer or the source of the wave

electromagnetic wave

electrical charge – a property of matter; electrons are negatively charged and protons are positively charged; the numbers of protons and electrons in a material determine the charge of the material electrical charge – physical property of matter that causes it to experience a force when placed in an electromagnetic field

electrical energy – a form of electric circuit – the pathway energy made available by the through which electrical current flow of electric charge through flows a conductor electric current – the flow of electricity through a circuit

electrical force – attractive or repulsive interaction between any two charged objects electromagnetic wave – oscillations of electromagnetic fields that carry energy through a medium or through a vacuum

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electron

GLOSSARY OF TERMS

electron – a negativelycharged subatomic particle of the electron cloud; involved in the formation of chemical bonds electron cloud – the area surrounding the nucleus of an atom where the electrons are found

gravity

frame of reference – a system that uses axes or background objects to measure the position or movement of an object freezing – the process by which a sample of matter changes from a liquid to a solid frequency – how often something occurs or is repeated during a set time

energy – controls the amount of change that can occur within gas – a state of matter in which a system; without enough the matter will take the shape energy, change cannot occur. and volume of its container energy transformation – the gravitational acceleration change of energy from one – acceleration caused by the form to another force of gravitation force – a push or pull on gravity – the force of attraction an object as a result of its interaction with another object that pulls objects toward each other; the force that controls or field the motion of our solar system formula – a group of letters, words, or numbers used to show how something works or is made © Accelerate Learning Inc. - All Rights Reserved

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halogens

GLOSSARY OF TERMS

halogens – any of the electronegative non-metallic elements in Group 7A of the periodic table heat – energy transferred between two objects of different temperatures, which will continue to move in a predictable pattern from warmer site to cooler site until all sites have reached the same temperature heat transfer – the thermal energy exchange between two objects of different temperatures; energy will continue to move in a predictable pattern from warmer site to cooler site until all sites have reached the same temperature

ion

indicator – organic compounds that exhibit different colors in solutions of different acidities inertia – an object’s tendency to resist changes in its motion insulator – material through which heat or electricity does not easily flow interference – the combination of two or more waves to form a resulting wave with an amplitude that is determined by the amplitudes of the combining waves ion – atoms (or groups of atoms) that have an electrical charge due to a different number of protons and electrons

inclined plane – a ramp that reduces the amount of force necessary to move an object up a height 484

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ioinic compound

GLOSSARY OF TERMS

ionic compound – a compound created when two or more oppositely-charged ions combine to form a formula unit, usually in the form of a crystalline structure ionization – the process of converting a neutral atom or molecule into an ion by adding or removing charged particles isotope – any two or more forms of an element with the same number of protons in the nucleus but a different number of neutrons

magnetic force

light wave – a wave of energy that provides us with the visible light spectrum, or the colors we see liquid – a state of matter in which the shape is variable and dependent on the shape of the container, the volume is constant, and the particles move independently within the substance magnet – an object that is surrounded by a magnetic field and that has the property, either natural or induced, of attracting iron or steel

lever – a simple machine made magnetic field – the area up of a bar that pivots on a around a magnet or moving fixed point electric charge that can exert a light energy – electromagnetic magnetic force energy that can be sensed by magnetic force – attraction or the eye repulsion that arises between electrically charged particles because of their motion

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magnetism

GLOSSARY OF TERMS

magnetism – a force that attracts or repels objects toward or away from each other; caused by electrons in a substance; iron is a popular magnetic element. mass – a measure of how much matter is present in a substance mechanical advantage – the number of times a simple machine multiplies force mechanical energy – energy produced by a machine or a moving part mechanical wave – a wave that propagates as an oscillation of matter, and therefore transfers energy through a medium

neutral solution

melting – when solids become liquids melting point – the temperature at which a substance changes states from a solid to a liquid molecular motion – the movement or motion of a particle in a substance molecule – the simplest unit of a chemical compound that can exist, which is formed when two or more atoms join together chemically motion – the change in an object’s position with respect to time and in comparison with the position of other objects used as reference points

neutral solution – solution medium – the material through with a pH of 7 which a wave travels

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neutron

GLOSSARY OF TERMS

neutron – a subatomic particle of the nucleus of an atom that is without charge and contributes to the mass of an atom nonpolar – two atoms equally share a pair of electrons with each other nuclear energy – the energy released during nuclear fission or fusion nuclear fission – the splitting of a nucleus into smaller fragments that results in the release of neutrons and a large amount of energy nuclear fusion – a reaction in which two light nuclei combine to produce a nucleus of heavier mass and result in the release of a large amount of energy

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pH scale

nucleus – the tiny, very dense positively charged region in the center of an atom; made up of protons and neutrons parallel circuit – a closed circuit in which the current divides into two or more paths before recombining to complete the circuit particle – the smallest possible piece of something periodic table – a table in which all the known elements are arranged by properties and are represented by one or two letters, referred to as chemical symbols pH scale – a scale ranging from 1 to 14 that measures the concentration of hydrogen ions in a solution

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phase (state of matter)

GLOSSARY OF TERMS

phase (state of matter) – different states of matter, including solid, liquid, and gas plasma – a fundamental state of matter similar to a gas that contains ions and free electrons polar – describes a molecule in which one or more atoms is slightly negative and one or more is slightly positive pressure – force exerted on matter through contact with other matter; affects melting and boiling points product – a substance produced during a chemical reaction proton – a positively-charged subatomic particle of the nucleus of an atom which contributes to the mass of the atom 488

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reactant

pulley system – a device consisting of a wheel over which a rope or chain is pulled in order to lift heavy objects radiation – the transfer of energy by the movement of electromagnetic waves or subatomic particles radioactive – the unstable condition of the nucleus that causes it to emit particles and lose energy radioactive decay – the spontaneous emission of radiation by an unstable nucleus radioactivity – the process by which unstable atomic nuclei become more stable by emitting energy reactant – a substance that takes part in and undergoes change during a reaction

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reflection

GLOSSARY OF TERMS

reflection – a change in the direction of a wave at an interface between two media that sends the wave back into the medium from which it came

sound energy

solubility – the ability of a substance to dissolve in another substance to form a homogeneous mixture

soluble – able to be dissolved in another substance to form a refraction – change in the direction of a wave as it passes homogeneous mixture through different objects at solute – a substance different speeds that dissolves in another series circuit – a closed circuit substance (solvent) to form a homogeneous mixture that has a single path for the current running from and to the solution – a homogeneous power source mixture composed of only one phase (solid, liquid, or gas) simple machine – a device that makes work easier, often solvent – an aqueous by reducing the amount of effort force needed to move an substance in which another substance is dissolved, or object spread homogeneously solid – a state of matter in sound energy – energy that which the shape is constant travels as waves through and rigid, the volume is the air or through water and constant, and the particles vibrates the eardrum upon vibrate in a fixed position contact

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sound wave

GLOSSARY OF TERMS

sound wave – a sound wave is the pattern of disturbance caused by the movement of energy traveling through a medium such as air, water, or any other liquid or solid matter specific heat – the amount of heat required to raise the temperature of one gram of an object by one degree speed – the measurement of the rate of change of position with respect to time

transmit

temperature – a measure of the average amount of kinetic energy of the molecules of a substance; average kinetic energy of all the particles in a material; measured by a thermometer in degrees (usually Celsius or Fahrenheit) energy internal to matter as the total kinetic energy (motion) of atoms and molecules in matter; the faster the atoms move, the warmer the matter.

thermal energy – a form of energy internal to matter as the subscript – a number written total kinetic energy (motion) of below and to the right of a atoms and molecules in matter; chemical symbol that shows the faster the atoms move, the the number of a specific type of warmer the matter atom present transmit – to pass something system – a group of interacting from one place to another or interdependent elements forming a complex whole, as in all the factors or variables in an environment or all the variables that might affect a science experiment 490

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valence electron

GLOSSARY OF TERMS

valence electron – the electrons in the outermost electron orbital of an atom that influence how an element will react with other substances valence shell – outermost shell of an electron

work

wheel and axle – a simple machine consisting of a wheel that spins on a central rod; used to lift heavy objects work – movement of an object as a result of the application of force

velocity – the rate of change of position volume – measures how much space the matter occupies wave – a rhythmic disturbance or oscillation that travels through matter or space, transferring energy wavelength – the distance between any two corresponding points on successive oscillations of a wave, such as from peak to peak

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Physical Science STEMscopes Georgia Student Notebook

I belong to:

a part of STEMscopes NGSS

Georgia_PhysicalScience_Book.indd 1

Physical Science Notebook

My teacher is:

developed by Accelerate Learning, Inc. & Rice University

(800) 531-0864

6/23/17 11:37 AM