Chapter 1
Chemistry: An Introduction
1.
The specific answer will depend on student experiences. In general, students are intimidated by chemistry because they perceive it to be highly mathematical, requiring a great deal of memorization, and having difficult technical vocabulary.
2.
Examples: a) physician (understanding cellular processes, understanding how drugs and blood tests work); b) lawyer (understanding scientific/forensic laboratory tests for use in court); c) pharmacist (understanding how drugs work, and interactions between drugs); d) artist (understanding the various media used in art work); e) photographer (understanding how the film exposure and developing chemical processes occur and how they can be controlled and modified); f) farmer (understanding which pesticide or fertilizer is needed and how these chemicals work); g) nurse (understanding how various tests and drugs may affect the patient's well-being).
3.
There are obviously many such examples. Many new drugs and treatments have recently become available thanks to research in biochemistry and cell biology. New long-wearing, more comfortable contact lenses have been produced by research in polymer and plastics chemistry. Special plastics and metals were prepared for the production of compact discs to replace vinyl phonograph records.
4.
There are, unfortunately, many examples. Chemical and biological weapons are still being produced in some countries. Although the development of new plastics has been a boon in many endeavors, this also increases our depletion of fossil fuels and our solid waste problems. Although many exciting new drugs and treatments have become available, the same biotechnology may lead to testing procedures for determining whether a person has a genetic likelihood of developing a particular disease, which may make it impossible or difficult for that person to obtain health or life insurance.
5.
This answer depends on your own experience.
6.
This answer depends on your own experience. Consider the following examples: oven cleaner (the label says it contains sodium hydroxide; it converts the burnedon grease in the oven to a soapy material that washes away); drain cleaner (the label says it contains sodium hydroxide; it dissolves the clog of hair in the drain); stomach antacid (the label says it contains calcium carbonate; it makes me belch and makes my stomach feel better); hydrogen peroxide (the label says it is a 3% solution of hydrogen peroxide; when applied to a wound, it bubbles); depilatory cream (the label says it contains sodium hydroxide; it removes unwanted hair from skin).
7.
Answer will depend on student experience.
Chapter 1
8.
The scientist must recognize the problem and state it clearly, propose possible solutions or explanations, and then decide through experimentation which solution or explanation is best.
9.
The steps are: (1) recognizing the problem and stating it clearly; (2) proposing possible solutions to or explanations of the problem; and (3) performing experiments to test the solutions or explanations.
10.
a. b. c. d. e.
Between 8 a.m. and 9 a.m. Between 12 a.m. and 1 a.m. The number of cars starts out low, increases until early morning, and then decreases and levels off. The number of cars then increases toward 5 p.m. and then drops off quickly. Between 8 a.m. and 9 a.m. many people are going to work and between 5 p.m. and 6 p.m. they are returning home. Check the traffic patterns on weekends and holidays. If the hypothesis is correct, you would expect not to see dramatic changes at 8 a.m. and 5 p.m. on these days.
11.
a. b. c. d. e. f. g.
Quantitative - a number (measurement) is indicated explicitly. Qualitative - only a qualitative description is given. Quantitative - a numerical measurement is indicated. Qualitative - only a qualitative description is given. Quantitative - a number (measurement) is implied. Qualitative - a qualitative judgment is given. Quantitative - a numerical quantity is indicated.
12.
A hypothesis is a tentative explanation for an observed event. So before proposing a hypothesis, repeated observations are necessary to make sure that the phenomenon repeats itself. A theory collects together hypotheses about all aspects of an event in an attempt to explain the event overall.
13.
A theory is a set of tested hypotheses that provides an overall explanation of an observed phenomenon. A hypothesis is a possible explanation for an observation. An experiment is some measurement or gathering of information we do to test a hypothesis. A natural law is a statement of some generally observed behavior, which we try to explain with our theory.
14.
False. Theories can be refined and changed because they are interpretations. They represent possible explanations of why nature behaves in a particular way. Theories are refined by performing experiments and making new observations, not by proving the existing observations as false (which is something that can be witnessed and recorded).
Chemistry: An Introduction
15.
"All objects dropped from a position above the ground fall downward" is a law. "For example, when an apple drops from a tree, it falls to the ground" is an observation. "This happens because apples are attracted to Earth" is a theory.
16.
Scientists are human, too. When a scientist formulates a hypothesis, he or she wants it to be proven correct. In academic research, for example, scientists want to be able to publish papers on their work to gain renown and acceptance from their colleagues. In industrial situations, the financial success of the individual and of the company as a whole may be at stake. Politically, scientists may be under pressure from the government to "beat the other guy."
17.
The practices of science and engineering are nearly identical, except instead of asking questions and constructing explanations, engineers define problems and design solutions.
18.
Criteria are the desired functions and features that a solution must satisfy, which engineers use to define an engineering problem and assess how successfully a solution fulfills these needs. Constraints are the limitations that are placed on a design, such as cost, time, and resource availability. Engineers make tradeoffs when they selectively favor one advantage of a design over another. A prototype is a test model used to assess a design before finalizing it.
19.
An engineering problem must be carefully defined in order for engineers to develop and compare different solutions in a measurable way.
20.
Most applications of chemistry are oriented toward the interpretation of observations that solve problems. Although memorization of facts may aid in these endeavors, the ability to combine, relate, and synthesize information is most important in the study of chemistry.
21.
When we study chemistry, at least at first, we try to be as general as possible. In this way, the basic principles learned can be applied to many situations. By learning to interpret and solve less complex problems, we can extend this strategy to more complex real-life situations.
22.
In real-life situations, the problems and applications likely to be encountered are not simple textbook examples. You must be able to observe an event, hypothesize a cause, and then test this hypothesis. You must be able to carry forward what has been learned in class to new, different situations.
Chapter 2
Matter
1.
has mass; occupies space
2.
Atoms are very tiny.
3.
a. b. c. d. e. f. g.
4.
When we say that a compound always has the same composition, we mean that the molecules of that compound always contain the same type and number of atoms of its constituent elements.
5.
Typically, the properties of a compound and the elements that constitute it are very different. Consider the properties of liquid water and the hydrogen and oxygen gases from which the water was prepared. Consider the properties of sodium chloride (table salt) and the sodium metal and chlorine gas from which it might have been prepared.
6.
The gaseous 10-g sample of water has a much larger volume than either the solid or liquid samples. While the 10-g sample of water vapor contains the same amount of water as the solid and liquid samples (the same number of water molecules), there is a great deal of empty space in the gaseous sample.
7.
Gases are easily compressed into smaller volumes, whereas solids and liquids are not. Since a gaseous sample consists mostly of empty space, it is this empty space that is compressed when pressure is applied to a gas.
8.
These are all physical properties.
9.
This is a chemical property: the red liquid bromine disappears and is replaced by a white solid.
10.
Magnesium is malleable and ductile.
11.
Magnesium burns in air.
compound compound molecular diatomic element atomic element molecular diatomic element compound atomic element
Matter
12.
Electrolysis is the passage of an electric current through a substance or solution to force a chemical reaction to occur. Electrolysis causes chemical changes to take place that would ordinarily not take place on their own. When an electric current is passed through water, the current causes the water molecules to break down into their constituent elements (hydrogen gas and oxygen gas).
13.
a. b. c. d. e. f. g. h. i.
Chemical; the scorch represents the oxidation of the material. Physical; the gas in the tires decreases in volume with temperature. Chemical; tarnish on silver is caused by reaction of the silver with sulfur or oxygen. Chemical; the oven cleaner contains sodium hydroxide, which converts greases in the oven into soaps. Chemical; an ordinary flashlight battery is constructed with a zinc casing, which serves as one of the electrodes. As the battery discharges, the zinc is oxidized. Chemical; the acids attack the calcium phosphate matrix of the teeth. Chemical; the charring represents the breakdown of the sugar. Chemical; iron in the blood catalyzes the decomposition of the hydrogen peroxide into oxygen gas (and water). Physical; this is just a change in state; carbon dioxide, only in the gaseous state, is still present after the sublimation.
14.
The bubbles suggest that a new product has been formed.
15.
solutions: window cleaner, shampoo, rubbing alcohol mixtures: salad dressing, jelly beans, the change in my pocket
16.
a. b. c. d.
mixture mixture pure substance mixture
17.
a. b. c. d. e.
homogeneous heterogeneous heterogeneous homogeneous The paper itself is basically homogeneous in appearance.
18.
a. b.
18-karat gold is a heterogeneous mixture Since the molecules are made of different atoms, as designated by different colors, this substance is a compound. As it turns out, this is water.