Next Generation Science Level 3 - Textbook B

Science for the Next Generation

Science Gra d e T h ree

Textbook

B

Next Generation Science Next Generation Science is based on the United States Next Generation Science Standards (NGSS). The series consists of full-color textbooks and full-color activity books for Grades K to 6.

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Charact

Fish are anim live in the oc can also be such as stre

Next Generation Science engages students with a highly visual presentation of the disciplinary core ideas in the textbooks and places an emphasis on applying scientific knowledge using NGSS practices through numerous scientific investigations. Next Generation Science sees engineering as an essential element of science education and as such is tightly integrated into both the textbooks and activity books.

Most fish re some give b

The Next Generation Science textbooks include the following features:

Think Deeply Topic-related questions for group discussion aimed at deepening students’ understanding of the topic.

In the Field

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Ecologist

If you are interested in all sorts of organisms and how they interact within their environment, then maybe you’d like to be an ecologist.

A community of living things and their interactions with their environment is called an ecosystem.

An ecologist is a scientist who studies these ecosystems.

Ecologists study a wide range of interactions and relationships within a given ecosystem. They may study small parts of an ecosystem such as small bugs living in the soil. They may also study large interactions such as fish populations in the ocean or how rainforests effect the atmosphere.

Ecologists usually choose a specific environment or living thing to study. For example, an ecologist desert or ocean environments. may only study A Clos er Look They may also choose to study one type of such as weather events or how human interaction Graphing Weather impact environments. activities Scientists are constantly collect ing data about the weath They often create tables er. and environment orthem graphs to help an ecologist, which you were If seaso understand nal changes in weath er. study?

Tables and charts are would you choose to organism way to comm also a useful unicate weather inform ation to people.

133 Let’s take a look at the yearly changes in weath er for San Francisco, United States .

Engineer It! Goes beyond inquiry by encouraging students to design, model and build to engineer solutions to defined problems.

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Average Daylight Hours – San Francisco Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 10 11 12 13 14 14.5 14.5 13.5 12.5 11.5 10 9.5

Average Precipitation

120 mm

– San Francisco

100 mm 80 mm

In the Field Inspirational sciencerelated professions to stir interest in sciencerelated careers.

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A Closer Look Invokes enthusiasm in science by presenting interesting topics beyond the syllabus.

60 mm 40 mm 20 mm 0 mm

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Jan

Feb Mar Apr May Jun

Jul

Aug Sep

Oct Nov Dec

Amazing Fact!

Interesting facts to build interest and enthusiasm.

fish gills

stingray

eat white shark

Fish have body parts well-adapted to life in water. They have gills to take in oxygen from the water. They have fins and tails to

teristics of Fish

mals that live in water. Most fish cean, which is salt water. Fish found in freshwater habitats, eams, rivers and lakes.

Extra information to build students’ knowledge base of the current topic.

A starfish has the word ‘fish’ in its name. Do you think a starfish is a fish?

Explain your answer.

help them swim.

Like reptiles and amphibians, fish are cold-blooded.

eproduce by laying eggs, but birth to live young.

Did You Know?

Think Deeply

Try This!

Optional hands-on activities to be conducted in groups or at home.

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Science Words Use the words to comp

Review

lete the sentences.

mammals metamorphosis fish insects pupa 1.

oxygen invertebrates amphibians larva chrysalis

Animals need a specia l part

of air called

2.

Animals with a backb one are

3.

Animals without a backb one

4.

vertebrates birds reptiles caterpillar

.

are called

are the only animals with

6.

are cold-blooded with

7.

Frogs and salamander s are

8.

A change in body form

.

a body covered in feathe rs.

a body covered in scales

or plates.

. They have smooth, moist

during an animal’s life

9.

live in water and have

10.

have six legs and a body

List the needs of anima ls.

List three vertebrate anima ls.

3.

List three invertebrate

4.

How are mammals differe nt from most other anima reproduction? ls in terms of

.

called

are animals with a body covered in fur.

They give birth to live young.

5.

1.

2.

cycle is called

gills to help them take

animals.

5.

List the characteristics

6.

List four kinds of reptile s.

7.

How is the life cycle of

8.

List the characteristics

9.

Describe insects in terms

of birds.

birds similar to that of

of their number of legs

10. Classify the anima ls as either

skin.

(a) .

reptiles?

of fish.

A worm-like butterfly egg.

12.

A caterpillar spins a coveri ng over its body, called a enters an inactive state called a .

, called a

and body parts. .

(b)

in oxygen.

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hatches from a

(c)

Discussion

(d)

, and

How does the weather change throughout the year in San Francisco?

77

Average Maximum Temp erature – San Francisco

25oC

Links students to the Next Generation Science Activity Book at the appropriate juncture.

vertebrates or inverte brates

divided into three parts.

11.

AB Activity

Topic-related questions and situations for class discussion to build a deeper understanding of topics.

20oC 15oC 10oC 5oC 0oC

AB

Jan

Feb Mar Apr May Jun

Jul

Aug Sep

Review

Oct Nov Dec

Activities 9.7 – 9.8

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Topical questions at the end of each chapter for formative assessment.

Science Words Lists the essential science vocabulary covered in each chapter.

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The 5E Model – Guided Inquiry The Next Generation Science series is based on the Biological Sciences Curriculum Study (BSCS) 5E teaching and learning instructional model.

The 5E model is centered on the idea that students understand science concepts best by using prior knowledge to pose questions and find answers through guided inquiry.

This hands-on approach, integrated with engineering and design skills, has students learn science by doing science. Teachers guide the learning process and are able to assess student performance by evaluating student explanations and the application of newly acquired knowledge and skills.

Engage

The Engage phase of the 5E model provides students with the opportunity to demonstrate their prior knowledge and understanding of the topic or concept. Students are presented with an activity or question which serves to motivate and engage students as they begin the lesson. Teachers identify and correct any misconceptions and gather data from students which will guide informed teaching and learning.

Essential to stimulating and engaging students is the use of mixed media such as colorful photos, illustrations and diagrams found throughout the textbooks and activity books. Next Generation Science also includes extensive digital resources such as narrated videos, interactive lessons, virtual labs, slideshows and more.

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Explore

This phase encourages exploration of concepts and skills through handson activities and investigations. Students are encouraged to work together and apply various process skills while gaining concrete, shared learning experiences. These experiences provide a foundation for which students can refer to while building their knowledge of new concepts. This studentcentered phase comes before formal explanations and definitions of the concept are presented by the teacher.

Explain

This phase follows the exploration phase and is more teacher-directed.

Students are initially encouraged to draw on their learning experiences and demonstrate their understanding of the concept through explanations and discussion. After the students have had the opportunity to demonstrate their understanding of the concept, the teacher then introduces formal definitions and scientific explanations. The teacher also clarifies any misconceptions that may have emerged during the Explore phase.

Elaborate

In the Elaborate phase, students refine and consolidate their acquired knowledge and skills. Opportunities are provided for students to further apply their knowledge and skills to new situations in order to broaden and deepen their understanding of the concept. Students may conduct additional investigations, share information and ideas, or apply their knowledge and skills to other disciplines.

Evaluate

This final phase includes both formal and informal assessments. These can include concept maps, physical models, journals as well as more traditional forms of summative assessment such as quizzes or writing assessments.

Students are encouraged to review and reflect on their own learning, and on their newly acquired knowledge, understanding and skills.

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Contents Unit 7 – Earth and Space 2 Movement of the Earth 4 The Earth’s Moon 8 Our Own Star – The Sun 10 Our Solar System 12 Review 23

Unit 8 – Rocks and Soil 22 Minerals and Rocks 28 Using Minerals and Rocks 38 What Is Soil? 41 Using and Caring for Soil 44 Review 47

Unit 9 – Weather and Climate 50 Understanding Weather 52 Measuring Weather 53 Extreme Weather 64 Weather and Seasons 66 Climate 70 Climate Change 76 Review 79 vi

Unit 10 – States of Matter 82 What Is Matter? 84 States of Matter 86 Heating Matter 90 Cooling Matter 92 Review 94

Unit 11 – Interactions and Forces 96 Position and Motion 98 What Is a Force? 106 Balanced and Unbalanced Forces 122 Predicting Motion 126 Review 129

Unit 12 – Forms of Energy 132 What Is Energy? 134 Sound 136 Light 140 Thermal Energy 144 Review 147

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Science Skills Scientists ask questions about the world around them. To find the answer to these questions, scientists use special skills to collect, analyze and interpret data. They communicate the things they find out.

Let’s look at how you can use these skills so you can be a scientist too.

Observing You make observations when you gather information about something using your senses. You can observe how something looks, feels, sounds, smells or tastes.

Scientists often use tools and instruments that allow them to observe things closely. Such tools include hand lenses, microscopes and telescopes.

It is important to accurately record your observations in a way that can be easily understood by others. You can make notes, and create charts and tables. You can also draw and label diagrams.

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Comparing and Classifying Scientists compare the things they observe.

To compare means to observe the properties or characteristics of two or more things and identify their similarities and differences.

Classification is the process of placing things into groups based on similarities in their properties or characteristics. Objects around us can be classified by the properties of the materials they are made of. Organisms can be classified by their features, such as the presence or absence of a backbone.

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Measure Measuring is an important science skill. It allows you to quantify your observations.

Distance, time, volume, mass and temperature are some quantities that can be measured.

To measure accurately, you often need to use tools such as rulers, beakers, thermometers and stopwatches.

Make a Model Scientists often construct models to predict, test and observe real-life phenomena.

Models can be physical objects, such a model of a miniature wind turbine to simulate electricity generation or a model of the Earth’s surface to simulate weathering and erosion.

Models can also be in the form of diagrams. A food web diagram is a model that shows the flow of energy in an ecosystem. A map is a diagrammatic model of an area of land or water.

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Infer You infer when you make a guess about something based on what you know or what you observe.

If you see footprints in the snow, you can infer that an animal has passed by after the last snowfall.

If you discover an animal jaw bone with large canine teeth, you can infer that the animal likely ate other animals.

Communicate You communicate when you show or tell other people what you find out.

Communication can be in the form of a written report, visual displays or an oral presentation.

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Scientific Method Scientists ask questions based on observations of the world around them. To find the answers to their questions, they carry out tests and investigations following the scientific method.

Why is it useful for scientists to follow the same scientific method?

The scientific method is a logical set of steps that is followed to help guide an investigation. It also helps to ensure the investigation is carried out fairly and in a manner that can be understood and repeated by other scientists.

Make Observations The scientific method begins by making observations about the world around you.

You may observe that plants in one area grow faster and taller than plants in other areas.

You may notice that you feel hotter in a darker-colored shirt than a lighter-colored shirt.

You may observe that ice melts faster in a cup made of one material than a cup made of another material.

Such observations lead you to ask questions about why these things occur.

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Ask Questions Before a science investigation begins, it’s important to ask questions about what you would like to find out.

Asking questions helps you to define the investigation. Your investigation should be designed to find the answer to your questions.

You can also used prior knowledge and experiences to provide possible answers to your questions.

Why does warm water cool faster in a metal cup than in a foam cup?

Do plants grow taller when fertilizer is added to soil?

Why do amphibians live near water?

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Make a Prediction Once you have asked questions based on your observations, it’s time to make a prediction and form a hypothesis. A hypothesis is a statement about what you think your investigation will show.

A hypothesis is more than just a guess. It is a statement based on knowledge you already have or things you have observed in the past.

Based on past gardening experience, you may predict that plants will grow faster and taller in humus-rich potting soil than in sandy soil.

Based on a previous investigation, you may already know that metal is a better conductor of heat compared to wood or plastic. These past experiences can help you predict the results of an investigation.

Why is it important to write a procedure that can be easily followed by others?

Plan and Carry Out an Investigation Once you have stated your hypothesis, it’s time to plan and conduct an investigation that will test your prediction. In planning your investigation, you should include all the materials you will need and a procedure that clearly shows the steps you will take to conduct the investigation.

Your materials and procedure should be written in a way that allows the investigation to be easily followed and repeated by others. In your procedure, include the data you will collect and the way it will be recorded.

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Variables An important part in a science investigation are variables. A variable is any factor that can be controlled or changed during the investigation. There are three main variables – the independent variable, the dependent variables and the controlled variables.

The independent variable is the one condition in the investigation that you can change. Usually it is the thing that is being tested. If you were investigating which materials are good conductors of heat, the independent variable would be the type of material.

The dependent variable is the factor that you measure or observe. The dependent variable should change due to changes in the independent variable.

In an investigation on materials that are good conductors of heat, the dependent variable could be temperature of water in a cup. You would expect the temperature of the water to change as you change the independent variable – the type of material the cup is made of.

Imagine conducting an investigation about the growth rates of different seedlings.

What would be the independent variable?

What would be the dependent variable?

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Imagine you were carrying out an investigation into the effect of temperature on plant growth. What would be your controlled variables?

The controlled variables are variables that do not change during the investigation.

Controlled variables could include the type and size of a container, the source and temperature of water and the types of instruments used to take measurements.

The purpose of the controlled variables is to ensure that the only influence on changes in your observations is due to the independent variable.

Collecting and Recording Data Make observations and collect data as stated in your procedure. The data should be recorded in an organized way that can be read and understood by others.

Often, data is recorded in a visual manner, such as charts, graphs and diagrams. Data can also be entered into computer software which can make it easier to analyze and present the data.

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Analyze and Interpret Data Once your observations have been accurately recorded, it’s time to analyze and interpret the data to see if your hypothesis is supported.

You analyze when you look closely at recorded data. You look for patterns to help explain your results. A pattern is when data repeats in a predictable way.

You interpret when you understand and explain what the data means. In interpreting data, you use your prior knowledge, experience, and skills to explain patterns and trends identified in the analysis of the data.

An important part of analyzing and interpreting is to check the accuracy of the data collected. If there are inaccuracies or inconsistencies in the data, you may need to adjust your procedure and repeat the investigation.

Draw a Conclusion By analyzing and interpreting your data, you reach a conclusion. Your conclusion is a summary of the data collected. Your conclusion should indicate the accuracy of your prediction.

Your conclusion should state whether your hypothesis was supported or not supported.

If your hypothesis was not supported, you may decide to form a new hypothesis and plan and conduct a new investigation. If your hypothesis was supported, you may wish to do further investigations to confirm the results or improve the accuracy of the data collected.

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Communicate The final step in a science investigation is to communicate your findings to others.

This allows you to share what you have discovered and also allows others to assess the accuracy of your investigation.

The people you communicate your results with may wish to conduct a similar investigation and compare results. They may also wish to conduct further investigations to find out more.

If they do, they’ll also communicate their results so others can learn from their investigations too.

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Scientific Method Flowchart Make Observations

Ask Questions

Construct Hypothesis Plan and Conduct Investigation Analyze and Interpret Data Form a Conclusion Hypothesis Not Supported

Hypothesis Supported

Communicate Results

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Science Safety In the Laboratory

Follow these safety rules when in your science laboratory or when carrying out any science investigation.

Do not enter the laboratory without a teacher.

Follow your teacher’s instructions.

If you have any questions or are unsure of what to do, raise your hand and ask your teacher.

Do not eat, drink, play or run in the laboratory.

Wash your hands with soap when entering and before leaving the laboratory. Dry your hands properly, especially if you will be working with electrical equipment. If any chemical or hazardous material gets on your hands, inform your teacher immediately.

Wear appropriate safety gear when carrying out scientific investigations.

Safety gear includes a lab coat, safety googles and gloves. Tie long hair back and do not wear open-toed shoes.

Be careful when handling sharp tools or working with burners and hot substances.

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o not panic if an accident occurs.

D Be aware of eyewash stations, fire extinguishers, exit doors and other safety equipment and procedures in case of an emergency. eep your workspace clean and K organized. Report any spills or breakages to your teacher. Clean up any spills straight away and dispose of the cleaning products safely. hen cleaning up, ensure all W materials and substances go into the correct bin or container. Do not pour any liquid down the sink unless your teacher has instructed you to do so. ook after the equipment you use and L return it to its proper location in the same condition you received it. Wipe your workstation down after use.

In the Field ake sure you are accompanied by an M adult when on field trips or doing other activities outside of the schoolyard. n long trips, make sure you take O enough water and food. Bring insect repellent if necessary. n sunny days, take Sun protection O such as a long-sleeved shirt, hat and sunscreen.

Try This!

Create a poster of the rules to be followed in your science laboratory or classroom.

Display the poster in a place for everyone to see.

o not touch plants, animals or other D organisms unless instructed to do so by your teacher.

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7

Earth and Space

In this chapter you will ...

• explain how the rotation of the Earth causes us to experience day and night.

• explain how the revolution of the Earth around the Sun causes parts of the Earth to experience seasons.

• describe the movement of the Earth’s moon.

• describe how the Sun affects the Earth.

• list the planets and other objects in our solar system.

What objects can be found in space?

How do the objects move?

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What objects make up our solar system?

Go Online!

Access interactive content relating to this topic on the NGScience website. ngscience.com

What is space exploration?

What data do scientists collect when they explore space?

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Movement of the Earth Rotation – Day and Night Why do we experience day and night on Earth?

In space, the Earth moves in different ways. One way the Earth moves is by spinning on its axis. An axis is an imaginary line that runs through the Earth’s center. This spinning movement on its axis is called a rotation.

As it rotates, part of the Earth is facing the Sun. This part of the Earth is lit up and experiences daytime. At the same time, the opposite side of the Earth is facing away from the Sun. This part of the Earth is in darkness and it is night-time.

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It takes the Earth 24 hours to complete one rotation. The repeating rotation of the Earth is why we experience the daily pattern of day and night.

The part of the Earth facing the Sun is in daytime. The part of the Earth facing away from the Sun is in night-time.

Amazing Fact!

The planets in the solar system rotate about their axis at different speeds.

This means the length of a day on each planet is different. One day on Jupiter takes just 10 Earth hours. One day on Venus takes 243 Earth days!

Go Online!

In what other way does the Earth move in space?

Observe how the Earth rotates on its axis and the daily pattern of day and night on the NGScience website.

QuickCode: B7M9

AB

Activity 7.1

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Earth’s Orbit and Seasons Amazing Fact!

As the planets are different distances from the Sun, they take different times to complete an orbit. This means the length of a year is different on different planets.

Mercury is the closest planet to the Sun. One year on Mercury is just 88 Earth days.

On the furthest planet from the Sun, Neptune, one year is 165 Earth years!

As the Earth rotates about its axis, it also revolves in a curved path, called an orbit, around the Sun. One complete orbit of the Sun is called a revolution. It takes the Earth 365 days to complete a revolution, which is one Earth year.

The Earth can be divided into two parts called hemispheres. The upper part of the Earth is called the Northern Hemisphere.

The lower part of the Earth is called the Southern Hemisphere.

Recall that the Earth rotates about its axis.

The axis is not straight up and down. It is tilted at an angle. This means that as the Earth orbits the Sun, one hemisphere is tilted towards the Sun and one hemisphere is tilted away from the Sun.

Go Online!

Observe the movement of the Earth around the Sun on the NGScience website.

QuickCode: K8J9

June

The hemisphere tilted towards the Sun gets more direct sunlight than the hemisphere tilted away from the Sun. This causes changes in weather patterns in different parts of the Earth at different times of the year. These changing weather patterns are called seasons.

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When the Northern Hemisphere is tilted towards the Sun, it gets more direct sunlight and is in summer. The Southern Hemisphere is tilted away from the Sun and gets less direct sunlight. It experiences winter.

When the Southern Hemisphere is tilted towards the Sun it is in Summer, while the Northern Hemisphere is in winter.

Think Deeply In December, many countries in the Northern Hemisphere are in winter.

What month would countries in the Southern Hemisphere be in winter?

March

December

September

How does the weather change from season to season in your area?

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The Earth’s Moon

Amazing Fact!

Many scientists believe the moon formed when a small planet crashed into the Earth.

Rock and dust were thrown into space. Gravity pulled the rock and dust together to form the moon.

In space, the force of gravity causes smaller objects to orbit larger objects. Any object that orbits another object is called a satellite. The Earth is a satellite of the Sun. The Earth’s moon orbits the Earth, so the moon is a satellite of the Earth. It takes the moon about 27.3 days to revolve once around the Earth.

It also takes the moon about 27 days to rotate once on its axis. So, the side of the moon facing the Earth is always the same.

On some nights, the moon appears in the sky as a bright circle. The moon appears bright because it reflects the light from the Sun. On other nights, the shape of the moon is different. The changing shape of the moon’s sunlit portion, as viewed from Earth, is called the phases of the moon.

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As the moon orbits the Earth, part of the moon is lit up by the Sun while the other part is in darkness. The moon appears to change shape because the part of the moon lit up by the Sun changes as the moon orbits the Earth.

When the whole side of the moon seen from Earth is lit up, we see a full, round moon. When only half of the side of the moon seen from Earth is lit up, we see the moon in the shape of a semi-circle.

What causes the phases of the moon?

AB

Activities 7.2 – 7.3

Think Deeply Why are we able to predict the shape the moon will appear in the sky?

Go Online!

Learn the names of the different phases of the moon in a video on the NGScience website.

QuickCode: H3C1

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Our Own Star – The Sun Amazing Fact!

If you could fly on a commercial plane from the Earth to the moon, it would take more than two weeks. To travel by plane from the Earth to the Sun would take about 20 years!

Think Deeply How would the Earth be affected if it were closer to the Sun? How would it be affected if it were further away?

If you look into the night sky on a clear night, you are likely to see many bright spots. These brights spots are stars. A star is a very large, hot ball of glowing gases. All stars are very large. They appear as small dots in the night sky because they are so far from Earth.

During the day, the brightest object in the sky is the Sun. The Sun is a star. It is the closest star to the Earth.

The Sun lights up the Earth during the day and keeps us warm. Without the light and heat from the Sun, there would be no life on Earth.

Although the Sun is the closest star to Earth, it is still very far away. The distance between the Earth and the moon is about 384,400 kilometers. The distance between the Earth and the Sun is about 150 million kilometers.

AB Activity 7.4 10

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Our Solar System Planets A planet is a large ball of rock or gas that revolves around a central star. The Earth, the planet we live on, is the only known planet to contain life. The central star that the Earth orbits is the Sun. In all, there are eight planets orbiting the Sun.

Venus Mercury

Mars Earth

Jupiter

These planets, their moons and other objects orbiting the Sun make up our solar system. In order of their distance from the Sun, the four closest planets are Mercury, Venus, Earth and Mars. These planets are called the inner planets. They are made up mostly of rock. Due to their close distance to the Sun, the inner planets are also much warmer than the planets further from the Sun.

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The outer planets are the four furthest planets from the Sun – Jupiter, Saturn, Uranus and Neptune. These planets are much larger than the inner planets. They are not rocky like the inner planets. Instead, they are made up mostly of gases. They are often referred to gas giants.

Amazing Fact!

Although AlthoughMercury Mercuryisisthe the closest planet to the Sun, closest planet to the Sun, Venus Venusisisthe thehottest hottestplanet planet ininour solar system!

This our solar system! Thisisis because becauseof ofthe themake makeup up of ofits itsthick thickatmosphere. atmosphere.

During Duringthe theday, day,the the temperature temperatureon onits itssurface surface can reach more than can reach more than440 440 degrees Celsius! degrees Celsius!

Uranus

Neptune Saturn

Did You Know?

Besides Mercury and Venus, all of the planets in the solar system have one or more moons.

Our planet, Earth, has just one moon. Mars has two moons. The planet with the most moons is Jupiter. It has 79 moons. Its largest moon, Ganymede, is larger than the planet Mercury!

Earth is the only planet in the solar system known to contain life. Why is this so?

Scientists once considered there to be nine planets in the solar system. This included a small icy planet beyond Neptune, called Pluto.

In 2006, scientists decided that Pluto was too small to be considered a planet and classified it as a dwarf planet.

AB Activity 7.5

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asteroids

Other Objects in the Solar System Besides the Sun, planets and their moons, what other objects can be found in the solar system?

Did You Know?

Beyond Neptune is a large belt of ice rocks called the Kuiper belt. The belt is around 2,000 times larger than the the asteroid belt and is also home to the dwarf planet Pluto.

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There are many different objects in the solar system. Some, such as space rocks, are natural. Others objects, such as communication satellites, have been sent into space by people.

One of the most commonly found objects in space are asteroids. Asteroids are large rocks that can range in size from just a few centimeters up to thousands of kilometers.

Most asteroids orbit the Sun in an asteroid belt between the planets Mars and Jupiter.

comet

Like asteroids, comets are made up of large chunks of rock. However, comets are also composed of ice, water and dust. Comets are often seen with a long tail which is mostly due to the dust that is left behind by the comet. The size of most comets ranges from around 700 meters to 20 kilometers.

Asteroids and comets often break up into smaller pieces and form meteoroids. Meteoroids have a size ranging from a grain of sand to one meter.

If a meteoroid enters Earth’s atmosphere, it becomes known as a meteor. Most meteors burn up completely before reaching the Earth’s surface. Have you ever seen a shooting star? It was most likely a meteor burning up in the Earth’s atmosphere.

Occasionally, a meteor doesn’t burn up completely as it enters the atmosphere.

A meteor that reaches the Earth’s surface is called a meteorite.

meteor

Amazing Fact!

About two billion years ago, a giant meteorite hit the surface of the Earth. It created the largest crater on Earth – the Vredefort Crater. It is more than 300 kilometers wide!

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Did You Know?

The Soviet Union launched Sputnik 1, the first man-made satellite, into space on October 4, 1957. Sputnik 1 completed a full orbit of the Earth every 98 minutes. After three months of orbiting the Earth, Sputnik 1 burned up on re-entry into the Earth’s atmosphere.

Some satellites in the solar system are manmade and have been launched into space by people. They are used for communication, weather forecasting and can provide us with accurate information about locations on Earth.

Some satellites are used to observe and gather data about other objects in the solar system, such as planets, moons and the Sun. Space telescopes are man-made satellites in space. They are used to see things further away and more clearly than telescopes on Earth.

Sputnik 1

communication satellite

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Hubble Space Telescope

Amazing Fact!

One of the largest is the Hubble Space Telescope.

It has been observing objects in the solar system and beyond since 1990. It has helped scientists learn many things about space.

Shortly after its launch in 1990, scientists noticed that the Hubble Space Telescope had trouble focusing on distant objects. Astronauts were sent into space to fit a new set of focal mirrors to the telescope.

Much like putting on a pair of glasses.

People often go on missions aboard space crafts launched into space by powerful rockets. The International Space Station (ISS) is the largest man-made object in space. The ISS is a giant space laboratory that orbits the Earth with up to nine astronauts on board. The astronauts carry out experiments about living in space in a hope to one day make living in space or even on other planets possible.

AB Activity 7.6 Powerful rockets are used to launch man-made objects and people into space.

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Go Online!

On July 20, 1969, pilot Buzz Aldrin landed the lunar module ‘Eagle’ on the surface of the Earth’s moon.

On July 21 at 2:56 a.m.

Commander Neil Armstrong stepped off the ‘Eagle’, becoming the first human to walk on the surface of the moon. Watch this amazing and historic event on the NGScience website.

QuickCode: T4P3

Space Exploration People have long been fascinated with space.

The searching, observing and collecting of data in space is called space exploration. Through space exploration, people are able to learn more about the objects in space, their properties and the patterns in which they move. Space exploration can be done using observation and monitoring instruments on Earth. It can also be done by sending objects or people into space.

To observe objects in space from Earth, scientists use powerful telescopes. A telescope is an instrument that makes objects that are far away look closer and clearer. This allows scientists to observe distant objects in greater detail.

The Gran Telescopio Canarias is one of the largest telescopes on Earth. It has been exploring space since 2009.

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Another way that scientists explore space is by sending objects into space to make observations and collect data. These objects, called space probes, include space telescopes, robots and satellites.

Space probes collect data about space objects and conditions.

They may also collect and analyze samples of objects or take photographs and videos. The data collected by space probes is sent back to Earth where scientists study and interpret the data.

People also explore space by venturing into space in space crafts. Scientists that travel into space, called astronauts, are highly trained in operating space crafts and living in space. In space, astronauts collect data and do experiments that cannot be done on Earth.

Large rockets are needed to get objects and people into space.

Amazing Fact!

The National Aeronautics and Space Administration (NASA) have sent five space robots, called rovers, to the planet Mars. They collect data about the planet’s surface and send the data back to Earth for analysis.

The latest rover to land on Mars, called Perseverance, left Earth on July 30, 2020 and touched down on February 18, 2021. On board the rover is a small robotic helicopter called Ingenuity.

Engineer It! Design and build your own model of an exploration robot to explore the surface of Mars. What data will it collect?

What features will it have to collect the data?

What types of experiments might astronauts carry out in space?

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A Closer Look

The International Space Station There are about eight billion people living on Earth. That’s a lot of people! Did you know that at this moment, there are a small group of people that don’t live on Earth – they live in space aboard the International Space Station.

The International Space Station (ISS), is a large satellite that orbits the Earth.

It’s the biggest man-made object in space and travels at a speed of about 27,000 kilometers per hour. In just one day, it orbits the Earth 16 times.

Since the year 2000, up to nine astronauts and cosmonauts have been on board the ISS at any one time. They are highly-trained to live and work in space.

Go Online!

Learn more about the International Space Station in a video on the NGScience website.

QuickCode: P4S6

International Space Station (ISS)

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You can think of the ISS as a giant science laboratory in space. Each day, the people on board carry out investigations about living in space for long periods of time. The data collected on board the ISS is sent back to Earth and shared with many different countries.

In what ways is living in space different from living on Earth?

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Science Words Use the words to complete the sentences. axis rotation orbit Northern Hemisphere Southern Hemisphere seasons solar system 1. A

revolution planet satellite phases of the moon asteroids comets meteoroids

star meteor meteorite space exploration telescope space probes

is a very large, hot ball of glowing gases.

2. The Earth spins on its every 24 hours.

. It completes one

3. Any object that orbits another object is called a

.

4. The changing shape of the moon’s directly sunlit portion, as viewed from Earth, is called the .

5. The Earth is divided into two parts. The upper part of the Earth is called the . The lower part is called the .

6.

are chunks of rock, ice, water and dust.

7. Asteroids and comets often break up into smaller pieces and form .

8. The Earth moves in a curved path, called an Sun. It takes the Earth 365 days to complete one

, around the of the Sun.

9. The revolution of the Earth around the Sun causes changes in weather patterns called .

10. A central star.

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is a large ball of rock or gas that revolves around a

11.

is the search, observation and collection of data in space.

12. A meteor that reaches the Earth’s surface is called a

.

is an instrument that makes objects that are far away 13. A look closer and clearer.

14. All of the planets, their moons and other objects orbiting the Sun make up our .

15. are large rocks that can range in size from just a few centimeters up to thousands of kilometers. .

16. A meteoroid that enters the Earth’s atmosphere is called a 17. are objects sent into space to make observations and collect data which is sent back to Earth for analysis.

Review 1. What causes the alternation of day and night on Earth?

2. What causes the changes in seasons on Earth?

3.

How long does it take for: (a) the Earth to complete one rotation? (b) the Earth to complete one revolution of the Sun? (c) the moon to complete one revolution of the Earth?

4. List the planets in the solar system. Indicate which are the inner planets and which are the outer planets.

5. Why are the outer planets much colder than the inner planets?

6. List three types of satellites sent into space by people.

7. What are space probes? What do they do?

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National Stadium, China

Guggenheim Museum, Spain

In the Field

Space Architect An architect is a person that designs structures such as skyscrapers, sports arenas, museums and houses. The purpose of their designs is to serve a function and have a form that is visually appealing.

The Guggenheim Museum in Spain and the National Stadium in China are examples of spectacular architectural designs.

One very unique type of architect that requires a lot of scientific knowledge and research is a space architect. A space architect designs space crafts and structures for humans to live in outer space!

The environment in space is not a friendly place for people to live. There is no air, temperatures can change from freezing to boiling very quickly and there is no gravity.

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These factors must be considered when space architects design space crafts and living quarters.

They must have very good knowledge about materials and their properties. They have to consider if materials will be safe and suitable for the fast changing environment in space. It’s not easy getting things into space, so the materials they choose also have to be lightweight and very strong.

Space architects focus mainly on how their structures will function and not so much on how they look. There aren’t many people around to admire the outside of a space station!

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8

Rocks and Soil

In this chapter you will ...

• describe minerals and rocks and where they can be found on Earth.

• describe how rocks are classified and distinguish between the three main types of rocks.

• describe soil and how it is formed.

• list the layers of soil.

• list ways people use soil and describe the importance of caring for soil.

What are rocks and minerals?

How are they used by people?

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Go Online!

What makes up soil?

Where does soil come from?

Access interactive content relating to this topic on the NGScience website. ngscience.com

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Minerals and Rocks What Are Minerals?

Amazing Fact!

Diamond is a mineral.

It is the hardest natural substance on Earth. The only other thing that can scratch a diamond is another diamond!

Minerals are non-living substances that are formed naturally in the Earth. They are usually found underground, in rocks and soil. Minerals are also found underwater in rivers, lakes and the ocean.

Minerals are made of chemicals. They do not come from the remains of living things.

You are already familiar with many types of minerals. Metals, such as gold, silver, iron and copper are minerals. Quartz, salt and talc are minerals too. quartz

Himalayan rock salt gold

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What Are Rocks?

Rocks are naturally occurring non-living things found on and under the Earth’s surface. All rocks are made up of one or more minerals.

Rocks can be found all over the Earth’s surface. They can be found on mountains and hills, in fields and valleys and along rivers and streams. Rocks line our coastlines and can be found underwater too.

In what ways are rocks similar to each other?

How can rocks be different?

AB

Activity 8.1

Amazing Fact!

The largest single rock formation in the world is Uluru in central Australia.

The gigantic rock reaches a height of over 850 meters above ground and another 2.5 kilometers below ground!

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Properties of Rocks Rocks are made up of tiny mineral particles called grains. Rocks can have different properties such as color, texture and arrangement of the grains that form them.

These rocks are different in color.

Try This!

In small groups, go into your schoolyard and collect small rocks. Discuss the properties of the rocks.

Classify the rocks in two different ways.

rough rocks

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These rocks are different in texture. smooth pebbles

These rocks have grains of different sizes.

The grains in these rocks are arranged in different ways.

What are some properties of the rocks in your schoolyard?

AB Activity 8.2

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How Do Rocks Form?

Scientists who study rocks, called geologists, often classify rocks by how they form. They can be classified into three main groups – igneous rocks, sedimentary rocks and metamorphic rocks.

Go Online!

Learn about different types of rocks and how they form on the NGScience website.

QuickCode: Q5F4

Beneath the surface of the Earth, temperatures can be very hot. It can be so hot that rock exists in a liquid (molten) form, called magma.

Igneous rocks form when magma cools and returns to a solid state.

Granite forms when magma cools slowly beneath the Earth’s surface.

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Sometimes, magma cools slowly beneath the Earth’s surface and forms rocks such as granite.

Other times, heat and pressure cause magma to break through openings in the Earth’s surface, called volcanoes. The magma flows onto the Earth’s surface as lava. The lava cools rapidly and forms solid rocks such as basalt.

Think Deeply How are magma and lava similar? How are they different? Draw a picture or create a Venn diagram.

Basalt is an igneous rock that forms when lava cools rapidly.

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sandstone

On the surface of the Earth, weathering and erosion break down rock and the remains of living things into small particles. Wind and water transport these particles to areas of dry land, into rivers, lakes and the ocean. Groups of these particles settle to form sediments.

Over many years, layers of sediments form and are pressed together forming new rock called sedimentary rock.

Common types of sedimentary rock include sandstone and limestone.

In sedimentary rock, it is often possible to see the layers of sediment from which they are formed. layers of sedimentary rock

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limestone

Metamorphic rocks are formed when igneous and sedimentary rocks are subject to heat and pressure beneath the Earth’s surface. Over time, the heat and pressure cause the rock to change form. The new metamorphic rock that forms has different properties from the original rock.

Heat and pressure beneath the Earth’s surface can cause limestone, a sedimentary rock, to change to marble, a metamorphic rock.

Think Deeply How is the formation of metamorphic rocks similar to the formation of igneous rocks?

Slate is another type of metamorphic rock. It is formed from the sedimentary rock, shale.

Slate is a metamorphic rock formed from shale.

Pink and gray layers of the metamorphic rock, gneiss.

Marble is a metamorphic rock formed from limestone.

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A Closer Look

The Rock Cycle Over millions of years, the weathering of rocks and soil on the Earth’s surface along with heat and pressure beneath the Earth’s surface cause rocks to continually change from one form to another. This process is called the rock cycle. igneous rock

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Trace the rock cycle diagram. With a classmate, discuss how rocks are formed at each stage.

AB Activity 8.3

sedimentary rock

metamorphic rock

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Using Minerals and Rocks Minerals and rocks are very useful to people.

They are used in many different ways.

Iron is a mineral we use to make the metal steel. We use steel to construct buildings and build bridges. Copper is a mineral used to make electrical wires and water pipes.

Aluminum comes from a mineral called bauxite. We use aluminum to make a variety of objects, such as cans, tin foil and parts of cars, boats and bicycles.

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Minerals such as gold and silver are used for making jewelry. Gems like diamonds and rubies are minerals too.

Calcium is a mineral found in dairy foods.

It helps to keep your bones strong and healthy. Many other foods contain minerals that help to keep us healthy.

Discuss some of the ways we use minerals from day to day.

Gold, diamonds and rubies are minerals commonly used to make jewelry.

AB Activity 8.4 Did You Know?

Fluoride is a mineral found naturally in water, rocks and soil. Fluoride is often added to toothpaste to strengthen teeth and help prevent tooth decay.

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Amazing Fact!

The Great Pyramids of Giza were built more than 4,000 years ago as tombs for the ancient rulers of Egypt.

The pyramids are made of more than five million limestone rocks.

Think Deeply What properties of rocks make them suitable to the ways they are used by people?

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Like minerals, rocks are used by people in many ways. We use rocks for building houses, roads and sidewalks.

We use rocks to build walls and decorate our homes and gardens too.

Look around your home or school. What are some ways we use rocks?

What Is Soil?

Soil is a mixture of weathered rock, minerals and other living and non-living things. In between the small pieces that make up soil are spaces that contain air and water.

An important part of soil is humus. Humus contains the remains of dead plants and animals and is often darker in color than other parts of soil. Humus adds nutrients to the soil which are essential to plants and other living things.

Think Deeply When gardening, people often add extra ‘topsoil’ to gardens. How does this help plants grow?

AB Activity 8.5

Many plants need soil to survive. Plant roots grow down into the soil and take in the nutrients, minerals and water the plants need to live and grow. As plants are the main source of food for people and other animals, soil is important to all life on Earth.

Many animals, such as ants, worms and other burrowing animals also live in soil.

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How Soil Forms Did You Know?

Compost is a soil very high in nutrients. It is made from the decomposition of organic matter – usually plant parts.

You can make compost by putting food scraps in a compost bin in your garden.

A compost bin is like an upside-down trash can.

compost

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Soil forms when wind, water and changes in temperature break down rocks into small pieces.

This process is called weathering.

The pieces of weathered rock are carried by wind and water to new places. The remains of dead plants and animals also form part of the developing soil.

As more weathered rock particles are added over time, soil begins to form in layers.

The soil layer closest to the surface of the Earth is called topsoil. This part of the soil contains lots of humus and is rich in nutrients. Topsoil also has large spaces for air and water. Most plants and soil-living animals get the things they need from the topsoil.

Below the topsoil is subsoil. Subsoil contains less nutrients and smaller spaces for air and water.

Below the subsoil is a layer of weathered rock fragments that sit on a layer of bedrock.

Soil forms in layers.

topsoil (organic layer)

subsoil

weathered rock particles

bedrock

Try This!

AB Activity 8.6

Use a clear plastic cup and art and craft materials to build a model to show how soil forms in layers.

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Using and Caring for Soil How People Use Soil Soil is used by people in many ways.

Farmers use soil to grow the plant crops that we eat for food. They also use soil to raise the animals that provide us with milk, eggs and meat. People also use soil in gardens to grow vegetables and fruits, or plants for decoration.

Plants that grow in soil are also used by people to make fabric, such as cotton, which is used to make clothes. Trees also need soil to grow. Trees provide people with the wood we need to build houses or burn for fuel.

AB Activity 8.7

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Caring for Soil Soil takes a long time to form. Just one centimeter of soil can take up to 1,000 years to form. Because it takes so long to form, it is important that we care for soil.

We can care for soil by preventing erosion.

Erosion can occur when we remove plants from the soil. This makes it easy for topsoil to be washed away by wind and water. When the topsoil is removed, many plants and animals cannot get the things they need from the soil that remains.

Soil can be harmed by pollution. Soil pollution occurs when harmful things, such as chemicals and rubbish, are added to soil.

Think Deeply How can water pollution affect land and soil pollution?

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Science Words Use the words to complete the sentences. minerals rocks magma igneous rocks

volcano lava sedimentary rock metamorphic rock

rock cycle soil humus weathering

1. Molten rock beneath the Earth’s surface is called 2.

.

is the breaking down of rocks into smaller pieces.

3. The part of soil that is rich in the remains of dead organisms is called .

4. On Earth, rocks are continually forming, weathering and changing form in a process called the .

5. Rock formed when igneous and sedimentary rocks are subject to heat and pressure are .

6. Layers of sediment press together to form

.

7. A is an opening in the Earth’s surface through which . magma flows as 8. All

are made up of one or more minerals.

9. the Earth.

are non-living substances that are formed naturally in

10.

form when magma or lava cools and solidifies.

11. is a mixture of weathered rock, minerals and other living and non-living things.

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12. Use the words in the box to label the soil layers. bedrock weathered rock particles topsoil subsoil (a) (b)

(c)

(d)

Review 1. List two minerals and describe how they are used by people.

2. Describe two ways people use rocks.

3. What is weathering?

4. Draw a diagram to show how rocks change form during the rock cycle.

5. How is humus different from subsoil?

6. How does soil form?

7. Describe two ways people use soil.

8. List two ways we can care for soil.

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In the Field

Geologists A geologist is a scientist that studies rocks, minerals, landforms and the processes that shape the surface of the Earth. They help us gain a better understanding of how rocks and minerals form and where they can be found in different parts of the Earth.

The data gathered and interpreted by geologists helps us to understand how the surface of the Earth changes over time and how landforms such as volcanoes, canyons and mountains form and change.

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Rocks and minerals are used by people in many ways. Geologists observe and test different rocks and minerals to find new materials.

Some geologists study earthquakes and volcanoes and can even help us to predict when an earthquake may occur or when a volcano may erupt.

Geologists spend a lot of time in nature collecting samples to study. So if you like the outdoors and want to learn more about the surface of the Earth, you’d love being a geologist – it rocks!

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9

Weather and Climate How can we describe and measure the weather?

How does the weather change between seasons?

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In this chapter you will ...

• collect and represent data to describe typical weather conditions.

• understand and describe how weather changes between seasons.

• describe climates in different regions of the world.

• design a solution to a weather-related hazard.

Go Online!

Access interactive content relating to this topic on the NGScience website. ngscience.com

How is climate different from weather? How are climates different in different regions of the world?

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Understanding Weather The Earth is surrounded by a layer of air called the atmosphere. Weather on Earth is caused by the heating of the air in the lower part of the atmosphere by the Sun. The heating and cooling of the air causes it to move in different ways. This movement of air is called wind. Air also contains water in the form of a gas called water vapor. The heating and cooling of air causes the water vapor to condense into clouds. This can cause it to rain or snow.

Weather is always changing. The weather in the morning may be different from the weather in the afternoon. Weather changes from day to day and from season to season. Weather is also different in different places.

AB

52

Activity 9.1

Measuring Weather How does the weather change from day to day? How can we measure weather?

By using different instruments and technology, we are able to accurately describe and predict weather. We can measure and predict temperature, the strength and direction of wind, or when it will rain. We are also able to predict extreme weather events like thunderstorms and hurricanes.

Temperature Temperature is a measure of how hot or cold the air around us is. It is measured in degrees Celsius (oC) or degrees Fahrenheit (oF).

Temperature is measured using a thermometer.

When the temperature is high, the weather can be described as warm or hot. When the temperature is low, the weather can be described as cool or cold.

thermometer

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Think Deeply The summit of Mount Everest is almost 9,000 meters. How would the air pressure at that height compare to the air pressure on the ground?

Air Pressure and Wind Like all matter, the air in the Earth’s atmosphere has mass. Air pressure is caused by the weight of the air pressing down on the Earth’s surface.

In lower areas of the Earth’s surface there is more air pressing down than high areas. So air pressure is higher at sea level and decreases with height.

Air pressure changes with temperature. When the heat from the Sun heats the surface of the Earth, the air surrounding the Earth is heated.

This causes the air to rise and the air pressure decreases.

The weather changes as the air pressure in an area changes. Generally, low air pressure will result in bad weather such as strong winds and rain. High air pressure is associated with calmer weather with clearer skies and little wind.

Air pressure is measured using a barometer.

barometer

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wind sock

Wind is moving air. When the heat from the Sun warms the air in one area, the air rises and the air pressure decreases. In places where the air is cooler, the air falls and the air pressure increases. Wind is caused when air moves from an area of high pressure to an area of low pressure. The greater the difference in air pressure, the stronger the wind.

anemometer

We can measure the speed of wind using an anemometer or a wind sock. These tools can also be used to measure the direction the wind is blowing.

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A Closer Look

Sea Breezes and Land Breezes A good example to help understand the relationship between temperature, air pressure and wind is to look at sea breezes and land breezes.

During the day, the Sun heats both the land and ocean, but the land gets heated faster. This causes the air above the land to become warmer than the air above the ocean. The air above the land rises and the cool air from the ocean moves to take its place. This causes wind to blow from the ocean to the land. This movement of the air is called a sea breeze.

During a sea breeze, wind blows from the ocean onto land.

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near-shore wind farm

During the night, there is no Sun in the sky to warm the surface of the Earth. Both the land and the ocean begin to cool. The land cools down faster than the ocean. The warmer air above the ocean rises and the cooler air from the land moves to takes its place. This causes the wind to blow from the land to the ocean. This movement of the air is called a land breeze.

Did You Know?

Wind farms are often located near the coast.

They use the energy in sea breezes and land breezes to generate electricity.

During a land breeze, wind blows from the land to the ocean.

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Precipitation Think Deeply Earth is the only known planet to contain water in three states. What are these three states and where can they be found on Earth?

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Water that falls from clouds in the sky is called precipitation. There are four main types of precipitation – rain, sleet, snow and hail.

The air in our atmosphere contains water in the form of a gas called water vapor.

When warm air rises, it begins to cool and the water vapor forms tiny water droplets in clouds. The droplets attach to dust and other particles. As more water droplets form and combine, they form larger drops.

The drops fall to Earth as rain.

sleet

In very cold temperatures, falling rain may freeze into small pieces of ice before reaching the ground. This type of precipitation is called sleet.

If the air in the clouds is cold enough, the water vapor can rapidly freeze and form snowflakes. Snowflakes fall to the ground as snow.

During a thunderstorm, raindrops in storm clouds can freeze to form balls of ice.

These balls of ice fall to the ground as hail.

hailstones

How is rain different from sleet, snow and hail?

AB Activity 9.2

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A Closer Look

The Water Cycle Water on Earth is constantly being heated and cooled. As this happens, water moves in a cycle between the surface of the Earth and the atmosphere. This process is called the water cycle.

The heat from the Sun causes the water in the ocean, lakes and rivers to change into a gas called water vapor. This process of changing from a liquid to a gas is called evaporation.

The water vapor in the air cools as it rises and changes to liquid water in the form of tiny water droplets in clouds. This process of changing from a gas to a liquid is called condensation.

evaporation

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condensation

The water droplets combine with other water droplets and eventually fall back to the surface of the Earth as precipitation. The precipitation flows on and under the ground into rivers, lakes and the ocean.

AB Activity 9.3 precipitation

Try This!

How long does it take for water to evaporate outside?

Plan and conduct an investigation to find out.

What factors affect the rate of evaporation?

Go Online!

Watch the water cycle in action in a video on the NGScience website.

QuickCode: C4D6

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Weather satellites orbit the Earth collecting and sending weather information back to Earth.

Weather Forecasting Weather scientists, called meteorologists, are constantly using technology to gather information about the weather. Weather stations all over the Earth collect data on temperature, the movement of wind, air pressure and precipitation. Buoys in the ocean collect data about currents, water temperature and wave height. Radars collect data about the movements of clouds and precipitation. In space, weather satellites are constantly orbiting the Earth, collecting and sending information about the weather back to Earth.

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Meteorologists use powerful computers to analyze and interpret weather information. By observing patterns in the weather, they are able to predict what the weather will be like in the future. These predictions are called weather forecasts. Weather forecasts are very helpful to people. They can help us to plan our day or week. They can also warn and help us to prepare for severe weather events, such as thunderstorms, hurricanes, floods and droughts.

Weather radars are able to monitor the movement of clouds and precipitation.

What information do meteorologists communicate to people during a weather forecast?

AB Activity 9.4 Meteorologists analyze and interpret patterns in the weather to predict what the weather will be like in the future.

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Extreme Weather Go Online!

A supercell is a large rotating thunderstorm with an updraft of wind in the center. Supercells often have very strong winds, frequent lightning and very large hail. Find out more about supercells on the NGScience website.

QuickCode: P4N6

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The weather can be different in many ways.

One day it may be warm and sunny. The next day it may be rainy or windy. Occasionally, there may be thunderstorms. During a thunderstorm there are often strong winds, heavy rain and lightning. Thunderstorms are an example of extreme weather. Other extreme weather events include hurricanes, tornadoes, floods and blizzards.

A hurricane is a rotating storm that forms over the ocean and moves onto land.

Hurricanes have very strong winds and precipitation. Hurricanes often include a series of thunderstorms. The heavy precipitation and large coastal waves can also cause floods.

A tornado is a rotating column of air that occurs on land, often during a thunderstorm.

There are very strong winds. Due to the strong upward movement of air during a tornado, there is little or no rain. However, precipitation can fall in the form of hail stones.

A blizzard, also called a snow storm, is a cold winter storm with heavy snow, sleet and strong winds. Snow may completely cover roads and buildings.

Engineer It! Draw a model of a house that can withstand the impact of a thunderstorm. Label and explain how each part helps withstand the storm.

Extreme weather can be dangerous to people and cause damage to property.

Engineers and architects often design buildings and structures to protect people against severe weather.

AB Activity 9.5 Discuss extreme weather events that occur in your area. What are some ways people reduce the impact of extreme weather?

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The United States is in the Northern Hemisphere. In June, it is summer.

New Zealand is in the Southern Hemisphere. In June, it is winter.

Weather and Seasons Go Online!

Observe how the Earth’s tilt and revolution around the Sun cause us to experience seasons on the NGScience website.

QuickCode: R4S7

Summer

The Earth is divided into two halves – the Northern Hemisphere and the Southern Hemisphere. As the Earth revolves around the Sun, sunlight hits one hemisphere more directly than the other. This causes us to experience seasons. In June, for example, the Northern Hemisphere is tilted toward the Sun and is in summer. The Southern Hemisphere is tilted away from the Sun and is in winter.

Northern Hemisphere

Winter

Southern Hemisphere

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Summer is the hottest season, occurring between spring and fall. Summer is the season with the most hours of daylight.

It has the earliest sunrises and the latest sunsets.

Fall is the season after summer. During fall, the temperature gets cool and the number of daylight hours begins to decrease. The leaves on some trees begin to change color and fall away. This will help them to save energy during the approaching winter.

During winter, the Earth is tilted away from the Sun. The weather is the coldest and the days are the shortest. The Sun rises later in the morning and sets in the late afternoon. In some parts of the Earth, winter is also the season when it is most likely to snow. The ground may be covered in ice and lakes and streams may freeze. Some animals become inactive or migrate to warmer places during winter.

As winter moves to spring, the number of daylight hours increases and the temperature gets warmer. Spring is the season for reproduction. Trees regrow their leaves and start to produce flowers.

Animals become active and also reproduce during spring.

summer

fall

winter

AB Activity 9.6

spring

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A Closer Look

Graphing Weather

Scientists are constantly collecting data about the weather.

They often create tables and graphs to help them understand seasonal changes in weather. Tables and charts are also a useful way to communicate weather information to people.

Let’s take a look at the yearly changes in weather for San Francisco, United States.

Average Daylight Hours – San Francisco Jan Feb Mar Apr May Jun 10

11

12

13

14

14.5

Jul Aug Sep Oct Nov Dec 14.5

13.5

12.5

11.5

10

9.5

Average Precipitation – San Francisco

120 mm 100 mm 80 mm 60 mm 40 mm 20 mm 0 mm

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Jan

Feb Mar Apr May Jun

Jul

Aug Sep

Oct Nov Dec

How does the weather change throughout the year in San Francisco?

Average Maximum Temperature – San Francisco 25oC 20oC 15oC 10oC 5oC 0 oC

Jan

AB

Feb Mar Apr May Jun

Jul

Aug Sep

Oct Nov Dec

Activities 9.7 – 9.8

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Climate Go Online!

Watch videos on the Earth’s different climates on the NGScience website.

QuickCode: D3A2

Climate describes the typical weather in a region over a long period of time. The equator is an imaginary line that runs through the center of the Earth. The climate in a region depends on its distance from the equator along with other factors such as rainfall, elevation or distance from the ocean.

Northern Alaska is far from the equator. The climate is very cold and dry. Most precipitation falls as snow.

The Amazon River Basin is close to the equator. It is warm and wet all year round.

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The climate in different regions can be different in many ways. Scientists often describe a climate by its average temperature and precipitation at different times of the year.

Describe the climate in your area. How does the climate change throughout the year?

The Egyptian desert has a hot and dry climate.

The Antarctic region is very far from the equator. It is very cold and dry all year round.

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Tropical Climates Think Deeply What types of precipitation fall in tropical climates?

Explain your answer.

Tropical climates are close to the equator. The temperature is warm and does not change much throughout the year. Precipitation is high all year round too.

Generally, tropical climates do not have four distinct seasons. Instead, they have a wet season and a dry season.

Many of the world’s rainforests are located in tropical climates. Being wet and warm all year round, tropical rainforests are the most diverse land habitats on Earth.

Why don’t tropical climates experience four seasons?

A tropical rainforest in Thailand.

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A park in a temperate climate during summer.

A park in a temperate climate during winter.

Temperate Climates Temperate climates are located between tropical climates and the Earth’s poles.

Temperate climates usually have four seasons – summer, fall, winter and spring. The temperature can change a lot from day to day and also from season to season. It is hottest in the summer and coldest in the winter.

Precipitation is lower than in tropical climates, but it may rain throughout the year.

How are temperate climates different from tropical climates?

Did You Know?

Compared to tropical climates, the weather in temperate climates can vary a lot from day to day.

It may be hot and sunny one day, then cloudy and cold the next.

A temperate climate during fall.

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Continental Climates Continental climates are climates located far from the ocean and usually in temperate areas.

The temperature in continental climates follows the seasons. It is often very hot in summer and cold in winter.

Precipitation is low and often occurs during summer. During winter, it may get cold enough for precipitation to fall as snow.

Coastal Climates Coastal climates are located close to the ocean, often between a mountain range and the coast.

Differences in air temperature cause wind and rain to move in a pattern between the ocean and the land. This results in a climate that is cool and wet.

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Alpine Climates The height of an area above sea level affects its climate. Generally, the higher above sea level, the colder the temperature. Alpine climates, also called mountain climates, are often cold all year round. It is often much colder at night compared to the day. Mountains have little soil and the ground is often covered in ice or snow. Generally, trees cannot survive in alpine climates.

Polar Climates Polar climates are cold all year round. There are cool summers and very cold winters. There are few trees and the ground is often covered in ice. Polar regions do not get direct heat and sunlight from the Sun. There are very long days in summer and very short days in winter.

Did You Know?

The Earth has two poles – the North Pole and the South Pole.

The region surrounding the North Pole is called the Arctic.

The region surrounding the South Pole is called the Antarctic.

AB Activity 9.9

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Climate Change Climate change describes the ways in which the Earth’s climate changes slowly over time.

In the past, the Earth’s climate has been colder and hotter than it is now. Scientists have discovered that human activities, mostly the burning of fuels, are causing the climate to get hotter much faster than normal.

This increase in temperature is causing ice in the Earth’s polar regions and glaciers to melt faster than normal, leading to rising sea levels..

These changes are affecting living things and people in many ways.

As the sea level rises, coastal areas around the Earth are at risk of flooding. Scientists have also discovered that hotter temperatures are causing more extreme weather. There are longer droughts and floods, stronger hurricanes and bigger wildfires.

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How will the melting of polar ice sheets affect the animals that live there?

Many plants and animals may not be able to adapt to the changes caused by climate change. Those unable to adapt are at a greater risk of becoming extinct.

AB Activity 9.10

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Science Words Use the words to complete the sentences. atmosphere water vapor temperature thermometer air pressure barometer

anemometer precipitation water cycle evaporation condensation meteorologist

weather forecast seasons climate equator climate change

1. Rain, sleet, snow and hail are forms of 2. Air pressure is measured using a

. .

3. of time.

describes the typical weather in a region over a long period

4.

is a measure of how hot or cold the air around us is.

5. Air contains water in the form of a gas called 6. The

.

is a layer of air that surrounds the Earth.

7. A prediction of what the weather will be like in the future is called a .

8. The of the Earth.

9. A

is an imaginary line that runs through the center is an instrument used to measure temperature.

10. is caused by the weight of the air pressing down on the Earth’s surface.

11. The is the movement of water between the surface of the Earth and the atmosphere.

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12. over time.

13.

is the ways in which the Earth’s climate changes slowly

The process of changing from a liquid to a gas is called

.

14. The process of changing from a gas to a liquid is called

.

15.

is a scientist that observes and makes predictions about

A the weather.

16. are weather patterns caused by the revolution of the Earth around the Sun. 17.

Wind speed can be measured using an

.

Review 1. List three elements of the weather that we can measure.

2. True or false. (a) The warmer the air, the lower the air temperature. (b) During a sea breeze, wind blows from the ocean to the land. (c) During a land breeze, wind blows from the ocean to the land.

3. What is hail?

4. What happens when water evaporates?

5. What is a weather forecast?

6. List three types of extreme weather.

7. What causes seasons?

8. What is the difference between weather and climate?

9. How are humans contributing to climate change?

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A Closer Look

The Greenhouse Effect In a greenhouse, heat from the Sun passes through the glass and heats the air inside. At night, when the temperature drops, the glass walls and roof trap some of the heat inside keeping the greenhouse warm. A similar thing happens when the Sun heats the Earth.

When the heat from the Sun warms the Earth, gases in the Earth’s atmosphere, called greenhouse gases, trap some of the heat in the Earth’s atmosphere. This is called the greenhouse effect.

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Some of the heat from the Sun is reflected back into space.

Greenhouse gases such as water vapor, carbon dioxide and methane occur naturally in the Earth’s atmosphere. However, the burning of fuels is causing an increase in the amount of greenhouses gases in the atmosphere. This is causing an increase in the average temperature on Earth.

Go Online!

Learn more about the greenhouse effect and how it affects the Earth in an animated video on the NGScience website.

QuickCode: M6P4

Greenhouse gases trap heat inside the Earth’s atmosphere.

How are the greenhouse effect and climate change related?

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10

States of Matter In this chapter you will ...

• describe matter and its states.

• describe the properties of solids, liquids and gases.

• describe how matter changes when it is heated.

• describe how matter changes when it is cooled.

What are the properties of solids, liquids and gases?

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Go Online!

Access interactive content relating to this topic on the NGScience website. ngscience.com

How does matter change when it is heated and cooled?

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What Is Matter?

Everything around you is made of matter. The air you breathe, the water you drink and even this book is made of matter. Matter is anything that has mass and volume.

Try This!

Find five objects in your classroom. Pick up each object and order them from the least to the most mass.

Use a balance to check if you were correct.

Think Deeply Chelsea placed two boxes of different sizes on each side of a balance. She noticed that the balance remained level. What can she infer about the mass of the boxes?

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Mass is how much matter an object has. Mass is measured using a scale or balance and is commonly measured in kilograms, grams, ounces or pounds.

We can compare the mass of different matter using a balance. The balance below shows that the boot has more mass than the shoe. The plastic ball and the apple are of similar size.

Using a balance we can see that the apple has a greater mass.

Volume is how much space the matter takes up. The basketball, beach ball and tennis ball all contain matter – air. The amount of space the air takes up in each ball is different.

Volume can be measured using measuring cups, measuring cylinders or measuring spoons. Volume is commonly measured in milliliters, liters, gallons and ounces.

Which beaker contains the greatest volume of water? How can you tell?

Order the balls from the smallest volume to the greatest volume.

Think Deeply Using a measuring cup and water, how could you measure the volume of the air inside a ping pong ball?

AB

Activity 10.1

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States of Matter Try This!

Find a solid object in your classroom. Use your senses of sight and touch to describe the object to a classmate.

The pencils stay the same shape whether they are in the cup or the pencil case.

There are three states or forms of matter – solids, liquids and gases. The properties of each state of matter is different.

What are the properties of solids, liquids and gases?

Properties of Solids The objects around you, such as your desk, books and pens are solids. Solids are matter that have a fixed shape and volume. This means the shape and volume of a solid does not change when it is placed in different containers. If you take a book and move it between different containers, its shape and volume does not change.

A rock is an example of a solid. Take a small rock and place it on a hard surface. Use you foot to press down on the rock. Notice that pressing down on the rock does not change its shape or volume. Solid matter cannot be compressed and does not change shape easily.

AB

3 86

Activities 10.2 – 10.3

Properties of Liquids Water, milk and cooking oil are examples of liquids. Like solids, liquids have a fixed volume.

This means the amount of space taken up by a liquid always stays the same.

Try pouring some water into a measuring cup and measure its volume. Pour the water into a measuring cylinder and measure its volume again. You’ll notice that the volume of the water does not change when placed in different containers. Like solids, liquids cannot be compressed.

Unlike solids, liquids do not have a fixed shape. The shape of a liquid depends on the container it is in. When you pour some milk from a carton or bottle into a glass, the shape of the milk changes, but the volume of the milk remains the same.

In what ways is a liquid different from a solid?

Try This!

Use containers of different sizes to demonstrate how a liquid flows to take the shape of its container. How can you find out if the volume of the liquid changes?

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Properties of Gases Gases are matter that can change in both shape and volume. You can’t always see gases, but they are all around you. The air you breathe is a gas. The water vapor released from a boiling kettle is also a gas.

Think Deeply What will happen to the shape and volume of the air inside a balloon when the balloon is popped?

When you blow up a balloon, you are filling the balloon with air from your lungs. You can press softly on the expanded balloon and change the shape of the gas inside. When you let go of the balloon, the gas spreads out in all directions and fills the room. Its volume changes.

We can also compress a gas to reduce its volume, like when adding air to a scuba tank.

Inside the scuba tank, the compressed air takes up much less space.

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Use the pictures to compare and contrast the properties of the different states of matter.

AB Activity 10.4

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Heating Matter There are three states of matter – solids, liquids and gases. Matter can change from one state to another when heat is added or taken away.

Melting When solid matter is heated, it changes from a solid to a liquid. Ice is a solid. When ice is heated it changes into liquid water. This process of changing from a solid to a liquid is called melting.

A candle is made of solid wax. When you light a candle, the heat from the flame causes the solid wax to melt into liquid wax.

What are some other examples where heat causes a solid to melt into a liquid?

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Evaporation How will liquid matter change when it is heated?

When liquid matter is heated, it changes into a gas. This process is called evaporation.

When it rains, puddles of water form on the ground. As the heat from the Sun warms the water, the puddles get smaller. A puddle gets smaller because the water evaporates into the air as a gas called water vapor. Eventually, all of the water evaporates into the air and the puddle dries up.

When water is heated to a high temperature, it boils. The bubbles you see in a pot of boiling water are pockets of gas. The bubbles of gas move to the surface of the water and into the air as water vapor.

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Think Deeply Where do the water dew droplets on grass come from?

What causes them to form?

Cooling Matter How does matter change when it is cooled?

Condensation Have you ever noticed water droplets form on the side of a cold glass of water? The droplets of water form when water vapor in the air cools as it comes in contact with the cold glass. This process of changing from a gas to a liquid is called condensation.

The water droplets that form on a mirror after a hot shower and the dew on grass on a cold morning are other examples of condensation.

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Freezing What change will occur when water is placed in a freezer?

Pour some water into an ice tray and place it in a freezer. After a few hours, you’ll notice that the liquid water has changed into solid ice. This process of changing from a liquid to a solid is called freezing.

Chocolate melts when it is heated in a pan. The liquid chocolate flows and can be poured into molds. When the liquid chocolate freezes, it becomes a solid with its own rigid shape.

AB Activity 10.5

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Science Words Use the words to complete the sentences. matter mass volume solid

liquid gas melting evaporation

water vapor condensation freezing

1.

is the process of changing from a solid to a liquid.

2.

is the amount of space matter takes up.

3.

is the process of changing from a liquid to a gas.

4.

matter has a fixed volume, but can change in shape.

5. A

can change in both shape and volume.

6. How much matter an object has is its

.

7.

is anything that has mass and volume.

8.

matter has a fixed shape and volume.

9. Water in the form of a gas is called

.

10. The process of changing from a gas to a liquid is called 11. The process of changing from a liquid to a solid is called

Review 1. What is mass and how can it be measured?

2. How can you measure the volume of a liquid?

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. .

3. Create a chart to compare the properties of solids, liquids and gases.

Provide an example of each state of matter.

4. Describe what happens to the volume of air in a balloon when the balloon bursts.

5. Describe the processes taking place in each picture. (a)

(b)

(c)

(d)

6. What change takes place when melted chocolate is cooled?

7. What change takes place when butter is heated in a pan?

8. What change takes place when water vapor cools on a cold glass?

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11 Interactions and Forces In this chapter you will ...

• describe the ways in which forces affect motion.

• distinguish and name contact and non-contact forces.

• determine cause and effect relationships of electric and magnetic interactions between two objects not in contact with each other.

• define a simple problem that can be solved by applying knowledge of magnets.

• provide evidence of the effects of balanced and unbalanced forces on the motion of an object.

• use knowledge of forces and motion to predict motion.

How can you tell that an object is moving? What causes things to move?

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What is a force? How do we interact with forces in daily life?

Go Online!

Access interactive content relating to this topic on the NGScience website. ngscience.com

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Position and Motion Position Look at the objects in the room below. How can you describe the location of the teddy bear?

Try This!

In small groups, take turns in describing the positions of objects in your classroom. The first person to guess the correct object is the winner!

When you tell where something is, you describe its position. Position is the location of something.

You can say the teddy bear is on the table and to the right of the spinning wheel. What other words can you use to describe the position of the teddy bear?

With a partner, take turns to describe the position of the other objects in the room.

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Distance and Direction

We can more accurately describe the position of an object by describing its distance and direction.

Distance is a measurable amount of space between one object and another. You can measure distance using different units. For objects that are close to each other, you can use units such as millimeters, centimeters and inches.

Go Online!

Learn more about position, distance and direction on the NGScience website.

QuickCode: E9V8

For objects further away, you can use meters, feet and yards. For even further distances, you can use kilometers and miles.

Direction is the course or line from one object to another. You can use words such as left, right, north, south, east and west to describe direction.

By using both distance and direction, you can describe position accurately.

The green car is two centimeters behind the orange car.

Try This!

Describe the position and direction of your house to your school.

My house is two kilometers north of my school.

AB

Activity 11.1 99

Describing Motion

Look at the skier in the picture. How does the position of the skier change?

We know that something has moved when it has changed position. When something is in the process of changing position, we say it is in motion. We can describe and measure motion in different ways.

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With a partner, compare the motions of the people and objects on these two pages. How are the motions different?

The skier is in motion when he is in the process of changing position.

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Go Online!

With a partner, go to the NGScience website and watch the ‘Describing Motion’ video. Take turns to describe the motion of different objects.

QuickCode: S7Q7

We can describe motion in many ways. A bowling ball moves in a straight line towards the pins. On a swing you move back and forth.

What’s your favorite ball sport?

What words can you use to describe the motion of the ball?

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Think about the different things in a playground. How can you describe your motion when you play on different equipment?

On a swing, you move back and forth. On a seesaw, you move up and down. On a carousel, you move round and round.

AB

Activity 11.2 A downhill skier moves from side to side in a zigzag motion.

What are some other ways we can describe motion?

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Measuring Motion Like describing the position of an object, we can use distance and direction to describe and measure motion.

An airplane travels about 3,200 kilometers in an easterly direction to fly from San Francisco to Denver.

Try This!

The fastest man on Earth can run 100 meters in less than ten seconds!

Time how long it takes you to run 100 meters. Compare your time with your friends.

Use distance and direction to describe your motion as you get from your home to your school.

You can also use time to describe motion.

Time is how long it takes for something to move from one position to another. You can measure time using seconds, minutes and hours.

AB

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Activities 11.3 – 11.4

Compare the motion of the bicycle and the motorbike. How is the motion different?

The motorbike is moving much faster than the bicycle. How fast or slow something moves is its speed. We can measure speed by calculating the time it takes an object to cover a certain distance.

Think Deeply It takes an airplane about two hours to fly from New York to Chicago. It takes a train about 20 hours to travel the same distance.

Which moves at the greater speed? How do you know?

If a cyclist rides 30 kilometers in one hour, we can say the speed of the cyclist was 30 kilometers per hour.

AB

Activity 11.5

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The tennis player uses push forces to throw and hit the ball.

What Is a Force?

Pushes and Pulls Whenever an object is in motion, it is because a force acted on the object, causing it to move. A force is a push or a pull.

A push is when you press something away from you. You use a push when you jump in the air. You use a push when you throw or hit a ball. The push force starts the ball moving.

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A pull is when you tug something closer to you.

You use a pull when you open a drawer or drag a suitcase.

The pull causes the objects to move.

There can be more than one force acting on an object. When you use a bow and arrow, you push and pull at the same time.

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How are forces used to move the golf ball differently? What effects do forces have on the motion of the golf ball?

Forces can have different strengths.

A large, strong force will move an object further and faster than a smaller, softer force.

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Compare the logs in the truck to the tree in the cart. Which would require a greater force to move? Why? Larger, stronger forces are required to move heavier objects.

The force required to move the truck is much greater than the force required to pull the cart.

AB

Did You Know?

We can measure the strength of a force using a spring balance called a Newton meter.

Activity 11.6

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Forces can affect the motion of objects in different ways.

When a player kicks the ball off the ground, it starts the ball moving.

Think Deeply How does the strength of a kick affect the distance the ball travels? Plan and conduct an investigation with your friends to find out.

Communicate your findings to other groups.

How do forces change the motion of a soccer ball during a match?

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Players kick the ball as they run, moving the ball in a zigzag motion.

Passing the ball from player to player causes the ball to speed up, slow down and change direction.

To prevent a goal, the goalkeeper uses a push force which stops the motion of the ball.

AB

Activity 11.7

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Contact Forces

There are many different types of forces acting around us. Some forces occur when objects are touching. They are called contact forces.

Pushes and pulls from people, animals and machines are example of contact forces.

In a baseball game, the pitcher is in contact with the ball when he pushes it forward.

To change the direction of the ball, there is contact between the bat and the ball.

A tow truck needs to be in contact with the car to affect its motion.

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Judo is a contact sport.

Players make contact as they use pushes and pulls to affect each other’s motion.

Discuss the contact forces you observe in daily life. How do the contact forces affect motion?

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Take a book and slide it along the classroom floor. What do you observe?

When you slide a book, you use a push force to set it in motion. The book slows down and comes to a stop due to a contact force called friction..

Friction is a force that opposes motion.

It occurs when the surfaces of objects rub together.

Rough surfaces produce more friction than smooth surfaces. Friction is also greater when surfaces press harder together.

Sometimes it is useful to reduce friction. A slide has a smooth surface to reduce friction. A snowboard has a smooth surface to help it move quickly on snow.

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Try This!

What are some examples of when it is useful to increase friction?

Have you ever seen someone rub their hands together when it is cold?

Try it now. What do you observe? What can you infer about friction?

As a force that opposes motion, we can increase friction to help things to slow down or stop.

The soles of shoes are often rough. This helps to increase the friction between the shoe and the ground and stops you from slipping.

A bicycle has rubber brake pads to increase friction when it presses against the wheel rim.

This allows the cyclist to slow down or stop moving.

AB

Activities 11.8 – 11.9

brake pads

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Non-contact Forces

Some forces can push and pull objects without touching. These forces can act at a distance and are called non-contact forces.

Place a magnet on a piece of paper and sprinkle iron filings over the magnet. What do you observe?

The pattern of the iron filings is the result of magnetic force. A magnetic force can act at a distance.

A magnet is an object with a magnetic force. A magnet can pull or attract objects made of certain metals such as iron and nickel. A magnet cannot attract objects made of plastic, wood, rubber or glass.

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A magnet has two poles – a North pole and a South pole. When the like poles of two magnets are brought together, they push or repel each other. When unlike poles are brought together, they pull or attract each other.

Engineer It! Design, model and build a useful tool that uses magnetic force. Describe how the tool works and how it uses magnetic force.

Like poles repel each other.

Go Online!

Unlike poles attract each other.

Many objects make use of magnets. Some doors used magnets to keep them closed. A maglev (magnetic levitation) train has magnets that repel it from the track. This reduces friction and allows the train to travel at fast speeds.

Magnets are also used for medical imaging and storing data on computer disks.

A maglev train uses magnets to hover above the tracks. This allows it to reach speeds of more than 400 kilometers per hour!

Watch a maglev train in action on the NGScience website.

QuickCode: P8T1

AB Activity 11.10

magnetic levitation train

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As the boy moves down the slide his hair stands on end! What force is causing this to happen?

Electrical forces are created when there are unbalanced electrical charges inside an object.

Opposite charges attract each other.

Like charges repel each other.

The plastic slide caused the boy to have an imbalance of like charges in his body. The charges in his hair repelled each other. The electrical force was strong enough to make his hair stand on end.

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You can create and observe the electrical force yourself.

Rub a balloon through your hair. Slowly pull the balloon away from your head. What do you observe?

Rubbing the balloon through your hair created two opposite static charges. The charges attract one another and make your hair stand up.

Notice that your hair and the balloon do not need to be touching to affect each other.

Electrical forces are non-contact forces and can act at a distance.

AB

Activity 11.11

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Think Deeply Gravity on the Earth’s moon is only one-sixth of the Earth’s gravity. With a classmate, talk about what it would be like to walk, jump and play different sports on the moon.

When skydivers jump out of an airplane, they are pulled towards the surface of the Earth.

What force is pulling them down?

All objects have an invisible force that pulls on other objects. The force is called gravitational force, or gravity.

The strength of an object’s gravitational force depends on it mass. Mass is the amount of matter something is made of.

The gravitational force of objects with a small mass, such as a basketball, is too weak to observe.

Compared to a basketball, the Earth has a much greater mass. The strong gravitational force of the Earth affects everything on its surface.

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It is the force of gravity that pulls you down when you jump in the air. It is the force that keeps everything on the Earth’s surface.

Gravitational force also depends on distance.

The closer objects are to each other, the greater the gravitational force.

AB Activities 11.12 – 11.13

Amazing Fact!

The object with the most mass in our solar system is the Sun. The gravitational force of the Sun keeps all of the planets and other bodies in the solar system in orbit around it.

Think Deeply How does a parachute help a skydiver reach the ground safely?

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Think Deeply An object in space can remain in motion with no forces acting upon it. Explain why this is so.

Balanced and Unbalanced Forces In a game of tug-of-war, one team pulls the rope in one direction and the other team pulls the rope in the opposite direction. What happens if both teams pull with the same force? What happens when one team pulls with a stronger force than the other team?

When both teams use the same amount of force in opposite directions, the forces cancel each other out. They are balanced forces.

When the forces acting on an object are balanced, there is no change in motion.

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To win a game of tug-of-war, one team must pull with greater force. The forces acting on the rope are not equal. Forces that are not equal and do not cancel each other out are unbalanced forces.

When there are unbalanced forces acting on an object, there is always a change in motion.

The forces are unbalanced and there is a change in motion.

The forces are balanced and there is no change in motion.

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Balanced Forces Think Deeply In small groups, describe all of the forces acting on the soccer ball in terms of strength and direction.

Is the net force zero? How do the forces affect the motion of the ball?

Look at the picture of the boy holding the soccer ball. Why is the ball not in motion?

The forces acting on an object have both strength and direction. An object at rest typically has multiple forces acting on it, but they add to give zero net force.

When the boy holds the ball and presses it against his side, all of the forces acting on the ball results in zero net force and there is no change in motion.

A soccer ball on the ground is being pulled down by the force of gravity. At the same time, the ground is exerting a push force in an equal and opposite direction. The forces are balanced – there is zero net force – and the ball remains at rest.

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Unbalanced Forces Forces that do not sum to zero can cause changes in an object’s speed or direction.

When the boy kicks the ball, he applies a force greater than the force of gravity. This creates an unbalanced force and sets the ball in motion.

When there are unbalanced forces acting on an object, a change in motion occurs. Unbalanced forces can cause an object to: • start moving • speed up • slow down • change direction • stop moving

AB Activities 11.14 – 11.15 125

Predicting Motion

You can use your knowledge of motion, the measurement of motion and forces to predict future motion.

On a seesaw, you can predict people will move up and down. On a swing, you move back and forth.

Use your knowledge of motion, gravity and friction to predict the motion of a marble when it is dropped into a bowl.

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Think Deeply How are airlines able to accurately predict the time it takes to travel from one country to another?

You can use information about distance, time and speed to predict the time you will arrive at school – whether you arrive by car, bus, walk or ride a bicycle.

Use your knowledge of motion and forces to predict the motion of a skydiver from the surface of the Earth, into the air and back down to Earth.

AB Activity 11.16

What are some other examples where we are able to predict motion?

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Science Words Use the words to complete the sentences. force friction gravitational force position distance

direction unbalanced motion speed time

contact forces non-contact forces magnetic force balanced electrical forces

1.

is the location of an object.

2.

is the measurable space between two objects.

3. The course or line from one abject to another describes

. .

4. An object in the process of changing position is in

5. is how long it takes for something to move from one position to another.

6. How fast or slow an object moves is its 7. A

.

is a push or a pull.

8. Forces that occur when objects are touching are called 9. Forces that can act at a distance are called 10.

. .

occurs when the surfaces of objects rub together.

11. A magnet is an object with

.

12. are created when there are unbalanced electrical charges inside an object.

13.

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pulls all objects towards the center of the Earth.

14. When the forces acting on an object are change in motion.

, there is no

15. When the forces acting on an object are in motion.

, there is a change

Review 1. List the forces that cause a ball to slow down and stop when it is rolled along the ground.

2. Describe and provide an example of a contact force.

3. True or false. Friction is a non-contact force.

4. List three forces that can act at a distance.

5. Why does a rocket need a large force to lift it into space?

6. True or false. An object at rest with zero net force acting upon it will remain at rest.

7. Describe what happens to an object when the forces acting on the object do not sum to zero.

8. Predict and describe the motion of the children. What are the forces that cause the motion?

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A Closer Look

Magnetic Resonance Imaging (MRI) Did you know that magnetic force can be used to create images of the inside of your body?

Some hospitals have large donutshaped devices called MRI machines.

MRI stands for Magnetic Resonance Imaging. So how does an MRI machine use magnets to see inside your body?

Patients lie on a bed and move through the donut-shaped cylinder which contains very powerful magnets. The magnetic force is turned on and off very quickly. Different parts of your body respond to the magnetic force in different ways. A computer records these changes and creates an image of the patient’s bones, organs and tissues.

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MRI is very helpful. It allows doctors to diagnose problems by studying the images without the need for surgery or causing any pain to patients.

Go Online!

Watch an MRI in action on the NGScience website.

QuickCode: E5G1

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12 Forms of Energy In this chapter you will ...

• list and describe different forms of energy.

• explain how sound is made and how it travels.

• describe ways in which sounds can be different.

• list sources and uses of light.

• describe how heat moves and how heat is used by people.

What is energy? How do people use energy in their everyday lives?

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What are some different forms of energy?

Go Online!

Access interactive content relating to this topic on the NGScience website. ngscience.com

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What Is Energy?

Did You Know?

Energy cannot be created or destroyed. It can be transferred or changed from one form to another.

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Everything that happens around you happens because of energy. You need energy to carry out daily activities like breathing, sleeping and playing sports.

Energy makes cars, buses and trains move.

Energy makes things feel hot, makes sounds and produces light.

All living things need energy to live and grow. Most of the energy on Earth comes from our Sun. Plants use the energy from sunlight to make food.

The energy in the food made by plants is passed on to animals and people when they eat plants.

There are different forms of energy.

Some forms include sound, light and heat. People use these forms of energy and others in many different ways.

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Sound What Causes Sounds?

Engineer It! Musical instruments make sound when a part of the instrument vibrates. Design and build your own musical instrument using art and craft supplies. Form a ‘band’ with your classmates. Play a song!

What are some sounds you hear from day to day? What causes the sounds?

We hear and make sounds all the time. We make sounds when we talk, clap or play a musical instrument. Objects like cars, sirens, phones and televisions make sound too.

Sound is a form of energy we can hear. All sounds are made when something vibrates.

Vibrations are rapid back and forth movements.

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When a bow is pulled across the strings of a violin, the strings vibrate and make sound. The vibrating strings cause the air around them to vibrate too. This creates sound waves. You hear the sound when the sound waves travel through the air to your ears.

Try This!

A sound is made when something vibrates.

Plan and conduct an investigation to show that sound can also cause an object to vibrate.

Did You Know?

When you throw a ball against a wall, it bounces back towards you. Sound waves travel in a similar way. When sound waves hit a surface, they bounce off the surface and move out in different directions.

You hear the sound that bounces back towards you as an echo. The echo is similar to the original sound.

AB

Activity 12.1

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Describing Sounds Try This!

Use a microphone and computer to record loud and soft sounds. Observe the size of the waves produced. What do you notice? What happens to the waves when you move further from the microphone?

Go outside, close your eyes and listen to the sounds around you. How can you describe the sounds your hear?

We can describe the sounds we hear in different ways. One way to describe a sound is by its volume. Volume is how loud or soft a sound is.

The sound of an airplane jet engine and the sound of thunder are examples of loud sounds.

The rustle of leaves and a whisper are examples of soft sounds.

A loud sound has more energy than a soft sound. Hitting a drum with a large force creates larger vibrations and a louder sound than if it were hit with a smaller force.

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Compare the sound of a rooster crowing to that of a lion’s roar. The volume of the sounds are similar – they are both loud sounds. However, they are different in pitch. Pitch is how high or low a sound is.

The crow of a rooster is a high-pitched sound.

The roar of a lion is a low-pitched sound.

The faster an object vibrates, the higher the pitch of the sound. The length and thickness of the vibrating object also affects its pitch. You can see this by making different sounds on a guitar.

A thin, short string produces a much higherpitched sound than a longer, thicker string.

Go Online!

Did you know doctors can use sound waves to see inside your body? Learn all about ultrasound on the NGScience website.

QuickCode: M6U2

AB Activity 12.2

Engineer It! Design a device that uses the volume and pitch of different sounds to send a message to another person.

How will you change the volume of the sounds? How will you change the pitch?

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The Sun is our main source of light.

Light Sources and Uses of Light

Amazing Fact!

The Sun is about 150 million kilometers from Earth. The light from the Sun takes about eight minutes to reach the Earth.

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What are some sources of light? How are sources of light used by people?

Light is a form of energy that allows us to see the things around us. Any object that gives out light of its own is called a source of light. Some sources of light, such as the Sun, lightning and fire are natural sources of light. Others, such as light bulbs and glow sticks are made by people – they are artificial sources of light.

During the day, the Sun is our main source of light. Plants use the Sun’s light energy to produce food. This provides energy to people and animals when they eat the plants.

Sunlight also helps us to see the things around us. At night, we often use lights to see. Lights are also used to send messages, such as telling cars when to stop and start at traffic lights.

Light is also used by people in devices such as telephones, televisions and computer monitors.

AB Activity 12.3

Think Deeply Light plays a very important role in boat navigation and safety. Lights of different colors tell people which direction to travel and warn them of danger. Boats are often required to display a raised, round, white light that can be seen from all directions. How is this useful?

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Properties of Light Light travels out from a source of light in a straight line. It continues to travel in a straight line until it hits an object.

We are able to see sources of light when the light travels from the source to our eyes.

We are also able to see objects that are not sources of light when light reflects or bounces off them and into our eyes.

The Earth’s moon is not a source of light. We are able to see the moon when it reflects the light from the Sun.

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Most objects are not sources of light. We see them when they reflect light.

What things can you see around you? What source of light are they reflecting?

Different surfaces reflect light in different ways. When light hits a dull or rough surface, such as a road, some of the light is absorbed or taken in. The light that is reflected bounces off in different directions. These surfaces appear dull.

Other surfaces reflect a lot of the light that hits them. The light bounces off in the same direction. These surfaces appear shiny.

A mirror reflects almost all of the light that hits it. That’s why you are able to see your reflection clearly.

Try This!

Draw an object you can see in your classroom. Use arrows to show how light reflects off the object and into your eyes.

AB Activity 12.4

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Thermal Energy Go Online!

Watch how heating and cooling matter affect its thermal energy in an animation on the NGScience website.

QuickCode: Z5J9

Matter is made up of tiny particles that are always in motion. How much these particles move is called thermal energy.

When an object gains thermal energy, the particles that make up the object move faster.

Its thermal energy increases and its temperature also increases.

When an object loses thermal energy, the particles that make up the object move slower. Its thermal energy decreases and its temperature decreases.

Imagine holding a cup of hot chocolate on a cold day.

How would your hands feel?

When you touch a cup of hot chocolate, energy moves from the cup to your hands and your hands warm up. This movement of energy that is caused by a difference in temperature is called heat.

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Thermal energy is the energy of the moving particles that make up matter.

Heat always flows from a warmer object to a cooler object. It continues to flow between the objects until the temperature of the objects is the same.

If you place a cool metal spoon into a cup of hot water, heat will flow from the hot water to the cool spoon. The temperature of the spoon will increase. Heat will continue to flow in this direction until the temperature of the water and the spoon are equal.

Think Deeply How does the heat from the Sun affect the objects on Earth? What changes occur to the objects?

cooler

The arrow shows the direction of energy flow within the spoon.

warmer

AB Activity 12.5

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Look at the materials used to make the pan. It has a metal body and a plastic handle.

Why were these materials used?

Try This!

In small groups, discuss some daily activities that make use of good conductors of heat and poor conductors of heat.

Create a table to show to other groups.

Think Deeply What makes certain clothes better heat insulators than others? How is this useful?

Some materials allow heat to pass through them more easily than others. Materials that allow heat to pass through them easily are called good conductors of heat. The metal used to make the pan is a good conductor of heat. It allows heat to flow easily from the hotplate to the food.

Materials that do not allow heat to pass through them easily are called poor conductors of heat, or heat insulators. The plastic handle on the pan is a poor conductor of heat. Heat cannot flow through the plastic easily, so it does not get as hot as the metal.

What are some other examples of objects that are made from good or poor conductors of heat?

AB Activities 12.6 – 12.7

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Science Words Use the words to complete the sentences. vibrations volume pitch natural source of light

artificial source of light reflect good conductors of heat poor conductors of heat

1. An object made by people that gives out light of its own is called . an 2.

is how loud or soft a sound is.

3.

are rapid back and forth movements.

4.

do not allow heat to pass through them easily.

5. We see objects when they

light.

6.

allow heat to pass through them easily.

7.

is how high or low a sound is.

8. An object in nature that gives out light of its own is a

.

Review 1. What causes sounds?

2. How does sound travel from its source to our ears?

3. How can we describe sounds?

4. Draw a Venn diagram to compare natural and artificial sources of light.

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5. List three ways we use light.

6. Describe how we are able to see the moon.

7. Describe how heat moves through the metal rod.

8. Sophie put a plastic spoon and a metal spoon into a hot cup of water.

Which spoon will feel hotter when she touches them?

Explain your answer.

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