INTRODUCTION TO CHEMISTRY
CHEMISTRY Section 1.2
CHEMISTRY FAR AND W I D E Section 1.3
T H I N K I N G LIKE A SCIENTIST Section 1.4
H O W TO STUDY CHEMISTRY
FEATURES DISCOVER IT! Solid, Liquid, or What? SMALL-SCALE LAB Introduction to Small-Scale Chemistry
SOLID, LIQUID, OR WHAT?
MINI LAB Bubbles!
You need a measuring spoon, cornstarch, a small bowl (such as a cereal bowl), and water.
CHEMISTRY SERVING ... SOCIETY Bad Breath May Be Good for You
1 . Add 3 heaping tablespoons of cornstarch to the bowl, then add 3 tablespoons of water.
CHEMISTRY IN CAREERS Chemist
2. Stir the contents of the bowl thoroughly and let stand for 5 minutes.
LINK TO FOOD SCIENCE Chemistry in the Kitchen
3. Slowly push your finger into the mixture. Repeat with your fist.
LINK TO ATMOSPHERIC SCIENCE Predicting the Formation of the Ozone Hole
5. Take a handful of the mixture and form a ball. Squeeze and release the ball several times.
To find out more about introductory chemistry, visit the following Internet site:
4. Quickly jab your finger into the mixture. Repeat with your fist.
What happens when you slowly push into the mixture with your finger or fist? When you jab it? When you squeeze the ball? When you release the ball? What condition seems to determine whether the mixture behaves like a solid or a liquid? When you have completed the chapter, return to this activity. What hypothe足 ses can you form? How can you test them?
objectives In the summer
of 1996, a group of scientists
that they might have found evidence of microorganisms a meteor that had its origins on the planet Mars. the claims of the scientists announcement
stunned the world because it suggested
on Mars long ago. The scientists chemistry.
that life might have
these alleged microorganisms
are still being scrutinized,
the existed by using
What is chemistry, and what are some of its different branches?
What Is Chemistry? Anyone who has ever watched a toddler explore a new environment knows that people are born with a natural curiosity about the world: a world of vivid colors and different textures, of simple and complex objects, of things that move and things that are permanently fixed. As the toddler grows, he or she learns to name observable things and, as much as possible, to figure out how they work. The desire to know more and more about the world grows as well. This desire, a lifelong attribute, is what compels humans to discover, build, and invent.
Define chemistry and differentiate among its traditional divisions List several reasons to study chemistry
key terms • • • • • •
chemistry organic chemistry inorganic chemistry analytical chemistry physical chemistry biochemistry
Chemistry is one branch of knowledge that grew from human curiosity about the world. Chemistry is the study of the composition of matter—the stuff things are made of—and the changes that matter undergoes. In fact, as you can see in Figure 1.2 on page 4, the Japanese symbols that make up the word for chemistry mean "change study." Much of chemistry is very practical and has obvious applications to everyday life. Perhaps you are wearing clothes made of synthetic fibers or natural fibers that have been dyed. The pan your dinner was cooked in may have a nonstick surface. Or perhaps you recently used nail-polish remover or hair spray. Other aspects of chemistry are theoretical, or without every day application. But what is theoretical one day may b e c o m e practical the next. For example, fifty years ago it would have been difficult to conceive of the impact of plastics or computers on our everyday lives.
Figure I.I Children learn by watching and doing. This toddler is learning about sand and ocean water, as well as exploring the uses of a pail, as she experiences a day at the beach.
Figure 1.2 The Japanese characters for chemistry literally mean "change study." Chemistry concerns the changes that matter
such as the rusting of metal, the transformation
of liquid water to
steam, and the burning of a match.
Traditionally, chemistry has been divided into five major areas of study. Organic chemistry was originally the study of substances from living organ isms. Today, with a few exceptions, organic chemistry is the study of essentially all substances containing carbon. Inorganic chemistry special izes primarily in substances that do not contain carbon. These are mainly substances from nonliving things. Analytical chemistry is concerned with the composition of substances. Finding minute quantities of a particular medication in blood requires the practice of analytical chemistry. Physical chemistry is concerned with theories and experiments that describe the behavior of chemicals. For example, the stretching of nylon can be explained using the concepts of physical chemistry. Finally, biochemistry is the study of the chemistry of living organisms. The processes of digestion, blood clot ting, and respiration, to name just a few, are explained by biochemistry. These five subdivisions of chemistry often overlap; for example, one cannot learn the composition of an organic or inorganic substance without being skilled in analytical chemistry. Chemistry is central to modern science and to almost all human endeav ors, as you can see from Figure 1.4. Today, many chemists work in teams with other scientists—biologists, geologists, physicists, physiologists, physi cians, and environmental scientists—as well as with engineers.
Figure 1.3 The flowering cactus and the sur rounding vegetation in this scene contain many organic
the rocks and the mountains in the background are made of inorganic compounds.
Why Study Chemistry? All the wonderful people and things that fill the world around you involve chemistry in one way or another! You are made from chemicals, and you use chemicals every dayâ€”when you breathe, drink a glass of water, wash your hair, or eat a snack. These c o m m o n activitiesâ€”and many, many
Figure 1.4 Chemistry is everywhere in your everyday life. In what ways do these photographs "say" chemistry to you?
Link FOOD SCIENCE Chemistry in the Kitchen Chemical reactions underlie your most wonderful successes (or dismal disasters) in the kitchen. The cut surfaces of apples, pears, and bananas turn brown
others—all involve chemicals and chemistry. Your natural desire to under stand how these things work is perhaps the best reason to study chemistry. Chemistry, with its focus on the workings of the natural world, helps satisfy your need to know and understand. Every day, you make choices: what to eat, what to wear, when and how much to study. As a citizen of this planet you will also be asked to act on questions of much greater importance. Is nuclear power acceptable or are there better alternative energy sources? What are appropriate responses to the problems of global warming and ozone depletion? Given limited resources, what deserves more support: the space program or finding a cure for cancer? Should experiments that involve manipulating heredity be regulated or forbidden? Knowledge of the basics of chemistry and other sciences can help you arrive at informed opinions and take appropriate actions on these questions. Although relatively few people become professional chemists, a career in chemistry can be a satisfying one, indeed. This introductory course can help you decide whether chemistry is a career for you. As a chemist, you might develop new products such as textiles, paints, medicines, or cosmet ics. Perhaps you would find methods to reduce pollution, clean up the environment, or prevent the destruction of the ozone layer. You could share your knowledge through teaching, analyzing pharmaceuticals, or checking the quality of manufactured goods.
upon exposure to oxygen in the air. Light, fluffy cakes result when baking powder reacts with acid in the batter to produce car bon dioxide. When sugar is heated, it forms dark-brown caramel. Heating the protein structure in eggs changes their texture from slimy to firm when they are boiled, scrambled, or fried. The tasty brown coating on the surface of roasted and grilled meats is formed by a complex series of chemical changes. Although tradition governs most of our behavior in the kitchen, food scientists are constantly searching for new and improved methods to prepare, present, and preserve food.
Very often, chemistry is used to attain a specific goal. The goal might be to formulate a new paint or adhesive or to set up procedures for a new medical test. Such goals are examples of applied chemistry, or chem ical technology. In applied chemistry, scientific knowledge is used in ways that can either benefit or harm people and/or the environment. Political and social debates about the uses of scientific knowledge are often really debates about the risks and benefits of technology. In addi tion to applied chemistry, there is pure chemistry. Like other pure sci ences, pure chemistry accumulates knowledge for its own sake. As you read on in this textbook, you will recognize many ways in which chemis try affects your life. And perhaps you will consider a career in chemistry! section r e v i e w 1.1 1 . Match the numbered terms in the right column with the lettered terms in the left column. a. technology
b. organic chemistry
(2) matter and its changes
e. analytical chemistry
2. List three reasons to study chemistry. 3. Explain the difference between Dure and applied chemistry.
Chem ASAP! Assessment 1.1 Check your understanding of the important ideas and concepts in Section 1.1.
CHEMISTRY FAR AND WIDE Every
to view the breathtakingly These colors—vivid
of visitors travel to New
oranges, yellows, are produced
which depends on changes in temperature
beautiful colors of the foliage. reds, and
appear as the trees approach the winter months no longer takes place. The bright pigments
by a complex
and hours of sunlight.
process is only one of many that occur all around you—and
Summarize ways in which chemistry affects your daily life Describe the impact of chemistry on various fields of science
What aspects of life involve chemistry?
Materials People have used chemistry to their advantage throughout history. Almost 3000 years ago, early chemists produced iron from iron ore by heating the ore with carbon. The invention of steel followed, in about 500 B.C. Steel and other mixtures of metals, such as brass and bronze, are important structural materials, as are the many recently developed ceramics. But today is primarily the age of plastics. Plastics, also called polymers, are gigantic molecules with many important properties. Chemists have learned to tailor these properties to meet specific needs. The most impor tant property of structural plastics is their high strength-to-weight ratio. A piece of plastic with the same weight as a piece of steel may be as much as five or six times stronger than the steel! A high strength-to-weight ratio makes polymers perfect for the protective weaving in bullet-resistant vests and for structural automobile body panels. The resulting reduction in the weight of the vehicle increases fuel efficiency. An automobile contains more than 500 pounds of polymers, if one counts the rubber, paint, sealants, lubricants, and upholstery.
Figure 1.5 People have always used the materials of chemistry. Bronze is a mixture that has been used since ancient times. Ceramic tiles on a space shuttle help to protect it from overheat ing. Light passing through optical fibers is used to transmit telephone messages. Optical fibers are made mainly from silicon dioxide (Si0 ), which is found in sand. 2
Your home contains a dazzling array of plastic items. Do you refriger ate leftovers in plastic food wrap, use nonstick cooking utensils, or water the lawn with a plastic hose? Perhaps you walk on a polyester or nylon car pet. You may be wearing wrinkle-resistant clothing woven from polyester fibers mixed with natural fibers of cotton or wool. The plumbing in your home could be made from polyvinyl chloride (PVC) pipe, and your walls may contain polystyrene insulation covered with a polyethylene vapor barrier. You have probably seen lawn and patio furniture made from plas tic, as well as kitchen counters covered with heat- and moisture-resistant polymers. To repair a piece of furniture, you might use an epoxy resin polymer to produce a bond stronger than the wood itself. Fabrics such as nylon and Dacron™ make up many of the clothes you wear everyday. Bowling balls, billiard balls, tennis rackets, and other sports equipment are made from polymers. None of these materials would exist if it were not for the efforts of chemists. But plastics are not the only materials produced by chemists. Blackand-white and color photographs are produced by the interaction of light with chemicals. Personal computers rely on silicon memory chips. Tele phone communications are transmitted over lines made from optical
Figure 1.6 In a continuing effort to conserve energy, efficient outdoor lighting methods, such as high intensity discharge, have been a focus of chemists. Chemists are also helping to develop renewable energy resources, such as solar power and wind power, to replace the ever-shrinking supply of fossil fuels.
fibers. These are only a few examples, but surely you get the idea.
Enerqy Population growth and increased standards of living around the globe create ever-greater demands for energy to power homes and factories. Where will this energy c o m e from? There are only two ways to provide it: conserve energy and produce more energy. Chemistry plays an essential role in both of these options. Some methods of conserving energy are obvi ous, others less so. But from energy-efficient fuels to safe and effective insulation materials to roadways lighted with sodium lamps, chemistry is creating new and exciting energy conservation methods.
Figure 1.7 The leaf of a green plant is an excellent solar collector; the energy of the sun is converted into the chemicals for life. What is this process
Most of our energy needs are filled by burning fossil fuels. But the supply of fossil fuels is limited. Because they are a nonrenewable resource, someday they will run out. Much of the world's petroleum is difficult or impossible to extract from Earth. However, an enormous reserve of petroleum could become available if tar sands and oil shales were coaxed into giving up the oil they contain. In addition, coal, lignite, and peat are potential sources of petro足 leum products. Even garbage can be converted into natural gas. Chemists are currently working on these and other exciting possibilities. Scientists are also working to provide new and perhaps inexhaustible sources of energy. Sunlight is the greatest source of energy available on Earth. Plants capture some of the sun's energy in the food-making process called photosynthesis. But only about 1% of the energy that strikes Earth is used by all the plant life in the world. Scientists are working to develop devices that efficiently convert the energy of sunlight into electrical energy. If they succeed, the electrical energy might be used to decompose ordinary water into hydrogen and oxygen. Hydrogen could then be burned as a renewable and nonpolluting fuel.
Figure 1.8 From entertainment devices to watches to medical appliances such as hearing aids, batteries have numerous applications. The development of practical electric automobiles is on the horizon. Just imagine what life would be like without batteries!
The development of batteries for the storage of energy is another goal of chemists. Early flashlight batteries, known as dry cells, did not last long in use. Dry cells were subsequently replaced by alkaline batteries, an improved design offering significandy longer life. The lithium-iodine battery is a recent advancement in the ongoing evolution of the battery. The lithium-iodine battery is an important improvement. Used in cardiac pacemakers, lithium-iodine batteries are small and efficient and can last as long as ten years. Electric automobiles will need powerful storage batteries to make them a practical alternative to vehicles with internal-combustion engines. Fuel cells under development are a promising source of pollution-free energy.
Figure 1.9 The sun's energy is produced by nuclear fusion. Nuclear power plants produce energy by nuclear fission.
Nuclear fission and nuclear fusion may also provide energy for the future. Nuclear fission, the process used in nuclear power plants, has been responsible for some serious nuclear accidents. However, if scientists learn enough about containing and controlling nuclear reactions and disposing of the waste, nuclear power may again achieve prominence as an energy source. Nuclear fusion, the process that produces the sun's energy, could be pollution-free. Research into producing energy from nuclear fusion on Earth is in its infancy. Scientists are currently concerned with methods for producing and containing the energy of nuclear fusion.
Medicine and Biotechnology Every year, the chemical industry produces millions of pounds of such med ically important substances as vitamin C, penicillin, and aspirin. However, the synthesis of vitamins and medicines is far from the only role that chem istry plays in the health and biological sciences. No endeavors have benefited more from advances in chemistry than medicine and biotechnol ogy. Much of this benefit derives from the ability of scientists to determine the spatial arrangement of atoms in complex biological molecules such as proteins. Many medicines are effective because they interact in a very spe cific way with biological molecules. Knowledge of the molecular structure of the target biological molecule greatly assists the design of safe and effective drug molecules. Medicines to reduce high blood pressure, high blood cho lesterol, and some cancers have been developed in this way. Chemistry is also providing new materials for medical applications. Diseased or weakened arteries can be replaced surgically with tubes made of Dacron™ polymers. Hipbones are replaced by substitutes made from metal alloys, or mixtures, of tungsten and cobalt. Much progress has been made in the development of synthetic blood and skin. Genes, the units of heredity in living organisms, are composed of deoxyribonucleic acid (DNA). The discovery of DNA's molecular structure and of many of the details of its role in heredity has resulted in major advances in biology and biotechnology. With the information gathered thus far and the continuing efforts of the Human Genome Project, scien tists worldwide expect to be able to identify and determine the molecular structures of all human genes. Such knowledge will have significant appli cations in medicine, genetics, agriculture, and even economics! Page 10
Figure 1.10 You are who you are because of genes, which are segments of DNA. Molecular models, such as this intricate segment of DNA, help
unravel the mysteries of the world around us.
Among other things, biotechnology involves the transfer of genes from one organism to another. Using this technology, human genes have been inserted into bacteria that then become factories for the production of human substances such as insulin, which is used to treat diabetes. In a few cases, a human genetic disease has been cured or its symptoms alleviated by replacing a faulty gene with a normal gene. Through biotechnology, com足 pletely normal sheep and cattle have been produced from a single adult cell of these animals by a process called cloning. The offspring of cloning, called a clone, is an exact genetic copy of its parent. Cloned cattle can pro足 duce human proteins in their milk. If in the future, cloned animals can provide a continuous supply of proteins that can be used to treat human diseases, one of the goals of biotechnology will have been realized.
Figure I.II More than an identical twin? Dolly was cloned from a single cell from her mother.
Agriculture Chemistry plays an important role in efforts to increase the world's food supply and to protect crops. Developing hardier and more productive plants is a key to these efforts. Studies of photosynthesis, the food-making process in plants, and nitrogen fixation, the process by which atmospheric nitrogen gas is converted into usable nitrogen compounds, may lead to the development of plants that use these processes more efficiently. Why do you think such plants would be valuable? Advances in the understanding of plant hormones, which regulate plant growth, represent another oppor足 tunity to increase the strength and viability of plants and, thus, increase the world's food supply. Page 11
Figure 1.12 Insecticides,
fungicides are used to protect crops from pests and disease. The effects of insect
corn smut, and wheat rust are apparent in these ruined
Figure 1.13 Do not take clean air for granted! As our roads grow more crowded, smog pollution becomes a problem chemists and others work hard to combat.
In addition to developing hardier and more productive plants, scientists are also focusing on safer and more effective ways to protect crops. In the past, insecticides, herbicides, and fungicides were quite nonspecific. Today, the trend is toward chemicals that are more specific for the condition they are designed to treat. For example, many newer insecticides are similar in molecular structure to natural protectants produced by the plants them selves. The discovery of more than 100 pheromones, which include insect sex attractants, is also being used in the battle against pests. These mole cules have proved effective in attracting and trapping such pests as gypsy moths and boll weevils. Chemists are also working to create more pestresistant and blight-resistant plants. Recombinant DNA technology is helping to breed plants with genetic resistance to their natural enemies.
The Environment Progress has its price: Every new development has both risks and benefits. Society, often through the political process, must decide whether the ben efits of a new development outweigh its risks. This is especially true for environmental protection. Chemists work with environmental scientists to identify pollutants, prevent or minimize environmental pollution, and clean up toxic wastes. One example of this teamwork involves the battle against the irritating smog that envelopes many of the world's large cities. Smog is produced by nitrogen oxide emissions from the internal-combustion engines of auto mobiles. To combat these pollutants, catalytic converters have been designed to remove nitrogen oxides from automobile exhaust gases. Pollu tion caused by burning fossil fuels such as coal is another example of a problem chemists and environmental scientists are tackling together. Burning coal produces sulfur compounds. Gaseous sulfur compounds are components of acid rain, which as you probably know is harmful to forests and lakes. Electrostatic precipitators and scrubbers help remove sulfur compounds from the gas emitted from power plants and factories.
Figure 1.14 Acid rain changed the appearance of this marble statue of George Washington from what it was 60 years ago (left) to what it is today (right). What causes acid rain?
The most abundant pollutant generated by humans, carbon dioxide, is produced by the combustion of fossil fuels. Earth's surface is warmed natu rally by the greenhouse effect, which is similar to the heating of an automobile's interior on a sunny day. The increasing amounts of carbon dioxide released into the atmosphere each year trap more of the sun's heat on Earth's surface than is natural, or even normal. The result of this increased amount of heat is global warming. Global warming could drasti cally alter weather patterns, sea levels, and agriculture around the world. In a worldwide effort, nations are working independently and collectively to reduce carbon dioxide emissions. Scientists are also concerned about the thinning of the ozone layer. The ozone layer protects Earth from the sun's harmful ultraviolet rays. Why is that important? One reason for the depletion of the ozone layer is the pres ence of chlorofluorocarbons, most notably Freon, which are a family of fluorine-chlorine-containing hydrocarbons that were originally used in refrigeration and air-conditioning equipment. Methyl bromide, used in agri culture, may also contribute to the thinning of the ozone layer. When depletion of the ozone layer was discovered, chemists provided an explana tion of the processes causing the deterioration. With this knowledge, they then began to design new compounds to replace the chlorofluorocarbons.
A T M O S P H E R I C SCIENCE Predicting the Formation of the Ozone Hole In the 1970s, F. Sherwood Row land and Mario Molina predicted that certain chlorine-containing compounds, such as chloro fluorocarbons (CFCs), might damage the ozone layer. The use of these compounds in aerosol sprays was banned in 1979. A decade later, British researchers showed that the ozone layer over the South Pole disappeared each year in the Antarctic spring. Since then, thinning of the ozone layer has been observed in other places around the globe. Work by atmospheric chemists has confirmed the idea of Rowland and Molina, and scientists now believe that a single chlorine atom can destroy millions of ozone molecules. In 1995, Row land, Molina, and Paul Crutzen, a German atmospheric chemist who had also studied ozone depletion, received the Nobel Prize in chemistry for their work.
Figure 1.15 There has been a steady rise in the global mean
since 1880. How would you describe the overall
trend? Page 13
Figure 1.16 This astronaut is walking on the moon to collect samples of the lunar surface, an example of which is shown in the inset photograph.
Astronomy and Space Exploration
Figure 1.17 Samples of the surface of Mars were analyzed by remote control. This photograph, taken by the Mars Pathfinder, shows the Sojourner making observations of the rock named Yogi. Why is such information valuable?
In the early nineteenth century, scientists first learned that by analyzing light transmitted to Earth by stars and other celestial objects, they could gain a "window" into the chemical composition of these objects. Obtaining similar information about the composition of the moon and planets is more difficult because these objects do not generate their own light. How足 ever, space exploration of Earth's moon and Mars is now providing some of this vital information. More than 850 pounds of moon rocks brought to Earth by various missions have been chemically analyzed. The moon rocks collected by Apollo astronauts were formed from volcanic material, sug足 gesting that vast oceans of molten lava once covered the moon's surface. Chemical analysis of the atmosphere of Mars reveals the presence of pri足 marily carbon dioxide, with smaller amounts of nitrogen, argon, oxygen, carbon monoxide, water vapor, and other gases. The Sojourner robotic vehicle, delivered to the surface of Mars by the Mars Pathfinder spacecraft, has analyzed and determined the chemical composition of Mars rocks. The composition of these rocks, particularly those known as conglomerates, indicates that a large amount of water once existed on the surface of Mars. Geologists are using this information to learn more about the formation of Earth and other planets, as well as to determine whether life as we know it could exist elsewhere in the solar system.
section r e v i e w 1 . 2 4. Explain how chemistry affects your daily life. 5. Name at least three areas of science in which chemistry plays an important role. 6. How might plant crops improve as a result of agricultural research? Why would such improvement be important? 7. Name at least three items that are made completely or partially of plastic.
ChemASAP! Assessment 1.2 Check your understanding of the important ideas and concepts in Section 1.2. Page 14
THINKING LIKE A SCIENTIST In March 1989, two chemists ordinary
Their "cold fusion"
that is, it involves
one nucleus of heavier mass and the release of
fusion, of two
of energy. In fact, the energy released from the sun is the result of nuclear
fusion. The prospect increasing
similar to that used for the electrolysis
you see, is a thermonuclear amounts
reaction was relatively
in the scientific
nuclei to produce
water, yet it caused much excitement reaction;
demands by rather ordinary
rushed to duplicate
dream of using cold fusion to obtain inexpensive, to the scientific
of energy to meet
means ignited much interest and
Describe the steps involved in the scientific method Distinguish between a theory and a scientific law
key terms • • • • • •
scientific method observation hypothesis experiment theory scientific law
But after many failures, the unlimited
the results of an experiment
must be reproducible
According if they
are to be accepted. What are the steps of the scientitic method?
The Scientific Method As you read the previous section, perhaps you found yourself thinking, "Who does these exciting and important things?" Scientists may seem to be special people because they obtain valuable—and sometimes spectacular—results. Nevertheless, as a Nobel Prize winner in science has said, science is about "ordinary people doing ordinary things." An important discovery may involve some luck, but one must be pre pared to recognize the lucky event. Alexander Fleming noticed that infectious bacteria failed to grow on portions of a bacterial culture where mold was growing. Fleming was very observant and scientifically prepared to realize the importance of this chance observation, which led to one of the greatest scientific achievements of all time. Do you know what Flem ing's discovery was? Most scientific advances, however, involve little or no luck. A logical, systematic approach to the solution of a difficult problem is often the best method, as well as the most powerful tool that ordinary people—you and scientists included—have at their disposal.
Figure I.I8 When you make observations, keep both eyes open.
The scientific method is one logical approach to the solution of scien tific problems. The scientific method is useful for solving many kinds of problems because it is closely related to ordinary common sense. Suppose you want to use a flashlight, but when you turn it on it does not light. You have made an observation—that is, you have used your senses to obtain information directly. In this case, your observation is that the flashlight does not light. This raises a question: What is wrong with the flashlight? You guess that the flashlight batteries are probably dead. By guessing, you have proposed a reason for your observation. You have made a hypothesis, or a proposed explanation or reason for what is observed. In the scientific method, scientists typically first observe something of scientific interest and then propose a hypothesis. Returning to your flashlight problem, you will probably want to test your hypothesis with an experiment. An experiment is a means to test a hypothesis. Most likely, you will put new batteries in the flashlight. If the Page 15
Figure 1.19 This outline of the method shows how
lead to the development
hypotheses and theories. Note that if experiments prove a hypothesis false, a new
must be proposed.
flashlight lights, you can be fairly certain from the one experiment that your hypothesis is true. Scientists also perform experiments to test their hypotheses. For the results of an experiment to be accepted, the experi ment must produce the same result no matter how many times it is repeated, or by whom. The repeatability of scientific experiments distin guishes science from nonscientific fields. Many different kinds of experiments may be needed to learn whether a hypothesis is valid. A scientific hypothesis is useful only if it accounts for what scientists observe in many situations. Suppose the flashlight does not work after you replace the batteries. What does this indicate about your hypothesis? When experimental data do not fit a hypothesis, the hypothe sis must be rejected or changed. The new or refined hypothesis is then subjected to further experimental testing. Again, returning to the flashlight problem, you might now decide to replace the light bulb because replacing the batteries was not helpful. The original, false hypothesis (dead batteries) has led to a new hypothesis (burnt-out bulb) and a new experiment to test it. The scientific method of observing, hypothesizing, and experimenting is repeated until the hypothesis fits all the observed experimental facts. Figure 1.19 outlines the major features of the scientific method. Once a scientific hypothesis meets the test of repeated experimenta tion, it may be elevated to a higher level of ideas. It may b e c o m e a theory. A theory is a broad and extensively tested explanation of why experiments give certain results. A theory can never be proved because it is always pos sible that a new experiment will disprove it. But theories are very useful because they help you form mental pictures of objects or processes that cannot be seen. Moreover, theories give you the power to predict the behavior of natural systems.
Figure 1.20 A scientific law summarizes results of many observations experiments.
ANALYSIS AND CONCLUSIONS
To test the hypothesis that bubble-making can be affected by adding chemicals to a bubble-blowing mixture.
1 . Label three cups 1, 2, and 3. Measure 1 teaspoon liquid dish detergent into each cup. Use the measuring cup to add 50 m L water to each cup, then swirl the cups to make a clear mixture.
1 . Did you observe any differences in your bubble-making using the mix tures in cup 1 and cup 2 ?
MATERIALS • 3 plastic cups • 3 teaspoons liquid dish detergent • measuring cup • 150 mL water •1/2teaspoon sugar •1/2teaspoon salt • drinking straw
2. Add1/2teaspoon table sugar to cup 2 and add1/2teaspoon table salt to cup 3. Swirl each cup for 1 minute. 3. Dip the drinking straw into cup 1, withdraw it, and blow gently into the straw to make the largest bubble you can. Practice making bubbles until you feel you have reasonable control over your bubble production.
2. Did you observe any differences in your bubble-making using the mix tures in cup 1 and cup 3 ? 3. What can you conclude about the effects of table sugar and table salt on your ability to produce bubbles? 4. Propose another hypothesis based on bubble-making and design an experi ment to test your hypothesis.
4. Repeat Step 3 with the mixtures in cups 2 and 3.
Scientific Laws A scientific law is a concise statement that summarizes the results of many observations and experiments. A scientific law describes a natural phe nomenon without attempting to explain it. Scientific laws can often be expressed by simple mathematical relationships. Gay-Lussac's law sum marizes what happens when a sealed, gas-filled container is heated: The pressure of a gas is directly proportional to the Kelvin temperature at con stant volume. Pressure can thus rise dangerously and lead to an explosion. Gay-Lussac's law states what happens; a theory explains why. section r e v i e w 1 . 3 8. Describe the steps involved in the scientific method. Give an example. 9. Distinguish among a theory, a hypothesis, and a scientific law. 10.
Why should a hypothesis be developed before experiments take place?
1 1 . In Chapter 2, you will learn that matter is neither created nor destroyed in any chemical change. Is this statement a theory or a law?
Chem ASAP! Assessment 1.3 Check your understanding of the important ideas and concepts in Section 1.3. Page 17
INTRODUCTION TO SMALL-SCALE CHEMISTRY PURPOSE The small-scale chemistry experiments in each chap ter of this textbook are designed to help you learn chemistry by doing chemistry. Each experiment pro vides the opportunity to interact with matter, interpret what you see, solve problems, and become more inventive and creative. You will be encouraged to ask questions, find ways to answer t h e m , and contribute your original ideas and discoveries to chemistry. Most of all, you will have fun learning chemistry. The small-scale experiments in this textbook have been carefully designed to minimize the risk of injury. However, safety is also your responsibility. You are expected to behave in a way that is consistent with safe laboratory practices. You are responsible for knowing and always following these laboratory safety rules. 1. Wear safety glasses at all times when working in the laboratory or when near someone else who is working in the laboratory. Do not rub your eyes because chemicals are easily transferred f r o m your hands to your eyes. 2. Recognize that all laboratory procedures involve some degree of risk. Read and listen to all direc tions carefully. When in doubt, ask your teacher. 3. Use full small-scale pipets for the carefully con trolled delivery of liquids, one drop at a time. 4. To minimize danger, waste, extra work, and cleanup, always use m i n i m u m amounts of chemicals when performing experiments. 5. Conduct only the assigned experiments, and do them only when a teacher is present and has given you permission to work. 6 . Know the location and operation of the following safety equipment: fire extinguisher, emergency shower, eye wash, fire blanket, and emergency exits. 7. Keep your work area orderly and free of personal belongings, such as coats and backpacks. Keep escape routes and walkways clear of classroom furniture.
8. Never taste any laboratory chemical, including the many food products you will study in the lab oratory. Consider these items to be contaminated with unknown toxic chemicals. Keep all food and drink out of the laboratory. Do not eat, drink, or chew gum in the laboratory. 9. Report any accident, no matter how minor, to your teacher. 10. Keep electrical appliances away f r o m sinks and faucets to minimize the chance of electrical shock, especially in the presence of water. Take care not to spill water or other liquids in the vicinity of an electrical appliance. 11. Do not handle heated or broken glass. In case of breakage, notify your teacher and your neighbor ing classmates. Do not use chipped or cracked glassware. Discard broken glassware according to your teacher's directions. 12. Protect your clothing and hair f r o m chemicals and sources of heat. Tie back long hair and roll up loose sleeves when working in the laboratory. Avoid wearing bulky or loose-fitting clothing. Remove dangling jewelry. Wear closed-toed shoes in the laboratory at all times. 13. Safety begins and continues with a clean labora tory. Report chemical spills immediately to your teacher. Clean up spills according to your teacher's directions. Warn other students about the identity and location of spilled chemicals. 14. Avoid contamination by cleaning up in a way that protects you and your environment. Always follow your teacher's cleanup and disposal directions. Carefully clean your small-scale reaction surface by absorbing the contents onto a paper towel, wipe the surface with a damp paper towel, and dry the surface completely. Dispose of the paper towels in the waste bin. Wash your hands thor oughly with soap and water.
HOW TO STUDY CHEMISTRY Does
objectives You saw it
on page 2 of this chapter and also on the cover of this textbook. The collage of images in the photograph deal about what chemistry
is and what you will learn
your course of study. Look at the images: Are some objects familiar? The beauty and excitement
says a great during
Explain why learning chemistry requires daily effort Describe the importance of writing in the study of chemistry
Others not so?
are captured in the images you see: the old
and the new; the macro view and the micro view; the applied and the theoretical. We wrote this textbook to help you gain a better understanding
of and appreciation
subject that explains your daily observations
offers an opportunity
to glimpse the future of scientific
How can you make your study of chemistry more effective and enjoyable?
Understanding and Applying Concepts Like anything else worth doing, learning chemistry requires some effort on your part. You have to read carefully, take thorough notes, and study often and effectively. But the payoff is well worth the effort. So find a quiet, welllit place, turn off the TV and the music, remove the distractions, pick up a pencil, and get to work! Chemistry deals with scientific facts—facts that can be discovered by making observations and doing experiments. And although your chemistry experience will include a great deal of observing and experimenting, the truth is that proving a scientific fact usually takes a lot of time and effort. To learn about a subject, therefore, it is often necessary to rely on information that others have previously discovered. In a way, learning chemistry is like learning a foreign language. You would not expect to learn the language without first familiarizing yourself with some of its vocabulary. Learning the language of chemistry means understanding the con cepts, or ideas, behind words. For example, even the simple, seemingly nonchemical word diamond contains many layers of chemical meaning. When most people hear the word diamond, they think of a glittering gem set into a piece of jewelry. But did you know that diamond is one of the hardest known substances? Or that it is a form of the element carbon? Or that it has a highly ordered molecular structure? Chemistry will help you
Figure l.21 The images shown here reveal a lot about the subject of chemistry. Can you explain the concepts they illustrate? When you have completed your study of this exciting subject, return to these images and find out exactly what you have learned!
make connections between the macroscopic world (the world you see) and the microscopic world (the world too small to be seen with the unaided eye). It is therefore important for you to understand the ideas behind the scientific facts and terms that you memorize. Indeed, if you understand the concepts, you will not need to memorize them—you will know them! You will also want to make connections between things you see in everyday life and the concepts you learn in your chemistry classroom and laboratory. Look around you. Think about the real world. Notice chemistry in your kitchen, on television, in magazines and newspapers, on the Inter net, and in your community. Try to visualize this chemistry at the level of atoms and molecules. Ask your teacher about the chemistry involved in your classroom and school. Try to relate your everyday experiences to your new chemistry knowledge.
Using Your Textbook There are some skills that you need to learn in order to understand chem istry. For example, you need to learn how to name chemical compounds, write chemical formulas, and interpret graphs. You also need to learn some techniques that are useful for solving chemical problems. Your teacher and this textbook will be very valuable in these efforts. This textbook will be your companion throughout your chemistry course. As its authors, we think the textbook is a "good read." But in truth, you should not read this textbook as you do a novel. Before reading a
Figure 1.22 Drawings can help you visualize those parts of matter that are too small to be seen even with a powerful microscope. Here you see the submicroscopic world of water, ice, and water vapor.
Chem ASAP! As
Figure 1.23 Chem ASAP!, your student CD-ROM, offers opportunities to access assessment exer cises, simulations, animations, and practice problems integrated with this textbook. Use and enjoy the Chem ASAP! CD-ROM as soon as possible.
chapter or section, it is a good idea to familiarize yourself with its contents by giving it a quick read-through. To get the most out of your reading, always have note-taking materials handy. What you make notes of tends to be retained longer than what you only see. So when you read or study, jot down notes, write equations, and solve Practice Problems as they appear. Compare your answers to the Practice Problems with those given. If they are not the same, redo the problem and try to identify your mistake. When you begin each section, read the objectives for the section and keep them in mind as you proceed. The objectives and key terms listed will help you to focus your reading. Be sure to look at the photographs, illustrations, tables, and graphs. Visual representations of information support and enhance learning and are often fun to look at. The figure cap tions contain a great deal of useful information, so read them. Try to understand the concepts illustrated in the visuals and interpret the trends shown in the graphs. Think about the concepts as you read. As you work your way through the textbook, you will see many refer ences to the Chem ASAP! CD-ROM. If this CD-ROM is available to you, take full advantage of it. It will help you visualize and understand the con cepts presented. In addition, Chem ASAP! offers extensive problem-solving help and many extra problems for you to do for practice. It also gives you many opportunities to evaluate your understanding of what you are learn ing. It will help you learn chemistry As Soon As Possible (ASAP!). When you have completed a chapter, go to the Student Study Guide. Read the section summaries and write the definitions of the key words in complete sentences to assess your understanding. Complete various ques tions and problems in the Chapter Review along with any other worksheets or assignments. What should you do if you have difficulty with a concept or problem? Work as hard as you can to achieve success. But remember that in most cases it is better to spend only a reasonable time on a concept or problem, make note of your difficulty, and move on. Ask your teacher or classmates for help with it during your next class. Page 21
Figure 1.24 Working in a group often leads to the biggest
On Your Own You can be even more successful in your study of chemistry if you go beyond the textbook. For example, draw your own diagrams to illustrate important concepts and definitions. Or make flashcards for important formulas, equations, terms, and definitions. Quiz yourself and your classmates often to evaluate your understanding. As you learned in Section 1.1, chemistry is often practiced as a group activity. Adopting this method might well enhance your study of chemistry. Many students form study groups with their classmates to work on difficult problems, talk through complex concepts, or gain a new perspective on what they are learning. Like writing, talking helps. If you cannot belong to a study group, explain chemistry to your friends, classmates, and family.
Tests and Quizzes Learning chemistry can be a lot of fun! However, it is very likely that as part of your study, you will be required to take tests and quizzes. Cramming for a test at the last second is never a good idea. It is much more beneficial to set aside a certain amount of time to study every day. How much time you set aside depends on how long it takes you to do the work. When test time comes, reviewing the work that you have already completed should be part of your preparation. Remember, exhaustion is your mind's enemy. Get enough sleep the night before the test. When you get the test, read it over quickly. Determine which parts of the test you can answer immediately or work out rapidly. Complete those parts first. Reserve any difficult questions for last. Show all of your work when answering problem-solving questions. After you have solved a numerical problem, evaluate your answer to be certain that it makes sense. If you have time, go over the entire test to check for errors. Remember, the best way to avoid panic and unwelcome surprises is to be well prepared. section r e v i e w 1.4 12.
Explain why it is important to study chemistry every day.
Why is chemistry best studied with a pencil in hand?
14. Explain the value of discussing chemistry with others. 15.
Briefly describe what your strategy for studying chemistry will be throughout the upcoming year.
Chem ASAP! Assessment 1.4 Check your understanding of the important ideas and concepts in Section 1.4. Page 22
Chemistry Serving... Society BAD BREATH MAY BE GOOD FOR YOU Allicin, which is what gives crushed garlic its strong odor, is easily converted into the more stable sulfurcontaining compounds ajoene (ah hoh EEN) and dithiin (dy THY in).
For more than 1000 years, people have claimed that eating garlic keeps y o u healthy. Is there any truth to this claim? Scientific evidence collected over the past several decades seems to show that garlic does indeed promote good health. Health researchers have found that people who eat a lot of garlic have a lower chance of getting stomach cancer, suffering from heart disease, or having a stroke than do people who eat little or no garlic. Although these findings point to health benefits from garlic, they do not indicate what in garlic causes the benefits. It has been the job of chemists to find out. The chemistry of garlic is not simple. Garlic contains more than 200 different compounds, many of which change when the cloves are cut or crushed. Cutting or crushing a garlic clove releases enzymes that cause a chain of complex chemical reac tions to take place. Some of the products last only a few minutes or a few hours before they change into more stable compounds.
Chemists and health researchers have investi gated the properties of allicin, ajoene, dithiin, and their chemical cousins. One of the properties they all share is the ability to kill microorganisms. In other words, they are antibiotics. As antibiotics, these compounds kill stomach bacteria that generate carcinogens. It is through this mechanism, scientists believe, that garlic reduces the risk of stomach cancer.
People who eat a lot of garlic have a lower chance of getting stomach cancer, suffering from heart disease, or having a stroke than do people who eat little or no garlic.
Chemists have focused their attention on the compounds in garlic that contain sulfur. These compounds seem to be garlic's "active ingredients." One of the most impor tant of these is allicin, a product of the reactions that begin when a garlic clove is cut or crushed.
Certain garlic compounds seem to fight cancer in other ways, too. In laboratory experiments, the compounds have been shown to reduce the size of tumors in can cer of the colon, lung, skin, prostate, and breast. Researchers believe that these sulfur-containing c o m p o u n d s s o m e h o w interfere with the growth process in cancer cells but have no effect on normal cells.
Garlic compounds can also prevent blood clots, which helps to reduce the chance of stroke. They also affect the diges tion and absorption of fats and thereby help lower the level of cholesterol and fat in the blood, which is important in preventing heart disease.
Although garlic's sulfur-containing c o m p o u n d s are responsible f o r its benefits, they are also the cause of its major drawback. The c o m p o u n d s are broken d o w n in t h e body into simpler sulfur c o m p o u n d s w i t h potent and unpleasant s m e l l s , w h i c h are exhaled t h r o u g h t h e lungs t o create "garlic breath."
Chapter 1 KEY TERMS analytical chemistry p . 4 biochemistry p . 4 chemistry p . 3 experiment p . 15 hypothesis p . 15 • inorganic chemistry p . 4
• • • • •
• • • • • •
observation p . 15 organic chemistry p . 4 physical chemistry p . 4 scientific law p . 17 scientific method p . 15 theory p . 16
CONCEPT SUMMARY 1.1 Chemistry • Chemistry is the study of the composition of matter and the changes that matter undergoes. • Analytical chemistry, biochemistry, inorganic chemistry, organic chemistry, and physical chemistry are the traditional divisions of chemistry. • Chemistry helps you to understand your world and to make informed decisions about scientific issues. Chemistry is an excellent career for some people. • Applied chemistry, or chemical technology, is chemistry used to attain a specific goal. Pure chemistry accumulates knowledge for its own sake. 1.2
Chemistry Far and Wide
• Chemistry reaches into such diverse areas as materials science, energy, medicine and biotechnology, agriculture, environmental studies, and astronomy and space exploration. • Progress has its price. Every new development has its risks and benefits. Society must decide in which direction the balance shifts.
CHAPTER CONCEPT MAP Use these terms to construct a con cept map that organizes the major ideas of this chapter.
Chem ASAP! Concept Map 1 Create your Concept Map using the computer.
1.3 Thinking Like a Scientist • The scientific method provides a logical approach to the solution of scientific problems. • The steps of the scientific method include observations, hypotheses, experiments, theories, and scientific laws. • An observation is information gathered directly by using the senses. A hypothesis is a proposed explanation or reason for what is observed. An experiment is a means to test a hypothesis. A scientific experiment must be repeatable. • A theory is a broad and extensively tested explanation of why experiments give certain results. A scientific law describes a natural phenomenon but does not explain it. 1.4 How to Study Chemistry • You can study chemistry alone or in groups. • It is important to learn the language and vocabulary of chemistry. • Your textbook is an important aid in your studies.
CONCEPT PRACTICE 16. Define chemistry. What is matter? 1.1 17. Describe the difference between chemistry and chemical technology. 1.1 18. Match each numbered term with a lettered term. 1.1 a. physical chemistry (1) composition b. organic chemistry (2) life c. analytical chemistry (3) carbon d. inorganic chemistry (4) behavior e. biochemistry (5) without carbon 19. Match each numbered photograph with the lettered field of chemistry it best represents. 1.2 a. materials science b. energy c. medicine and biotechnology d. agriculture e. environment f. astronomy and S D a c e
20. How might advances in energy research affect your life? 1.2 21. Why is the ozone layer surrounding Earth important? 1.2 22. Give at least two benefits of replacing some of the steel in automobiles with plastics. 1.2 23. What is the purpose of an experiment as part of the scientific method? 1.3 24. Describe two situations in which you used at least part of the scientific method. 1.3 25. You perform an experiment and get unex足 pected results. According to the scientific method, what should you do next? 1.3 26. Which of the following is not a part of the scientific method? 1.3 a. hypothesis c. guess b. experiment d. theory 27. Compare and contrast the study of chemistry with the study of a language. 1.4 28. Which statement about the study of chemistry is false? 1.4 a. The chemistry textbook is an important study aid. b. Chemistry is mostly memorization. c. It is better to study on a regular basis than to cram before a test. d. A study group is beneficial. e. Discussing chemistry with family and friends is helpful.
CONCEPT MASTERY 29. You find a sealed box with strings protruding from three holes, as shown in the diagram. When you tug string a, it becomes longer and string c becomes shorter. When you tug string b, it becomes longer, but strings a and c are unaffected. Make a diagram showing the arrangement of the strings inside the box.
30. You have a sore throat, so you go to the doctor. The doctor examines your throat and says she thinks you have strep throat. She takes a sam足 ple to test for strep bacteria. What parts of the scientific method is the doctor applying? 31. You perform an experiment and find that the results do not agree with theory. Is something wrong with your experiment? 32. Explain why chemistry might be useful in any career.
CRITICAL THINKING 33. Choose the term that best completes the second relationship. a. seed:plant data: (1) theory (3) experiment (2) techniques (4) scientific method b. hub:wheel chemistry: (1) tire
c. part:whole theory: (1) scientific method (2) experiment
(3) observation (4) law
34. Comment on the idea that science accepts what works and rejects what does not work. 35. Occasionally you may read about important discoveries being made accidentally. Louis Pasteur said, "Chance favors the prepared mind." Are these two statements contradictory? Explain. 36. Criticize the statement, "Theories are proven by experiments." 37. Refer back to question 28 and provide an explanation for each statement that is true. Correct the statement that is false.
38. For each of the following observations, develop an appropriate question and hypothesis. Then describe an experiment you might use to test your hypothesis. a. After riding your bicycle for several hours on a warm day, the air pressure in the tires has increased by 9 pounds per square inch. b. The slices of apple you left out on the kitchen counter have turned brown, while those in the refrigerator have not.
41. Design a study strategy or plan that you could use throughout this course to help you learn chemistry. Discuss your plan with your teacher, share it with the class, and use it during your study of chemistry.
39. You observe that when you place a jar over a lit candle, the flame goes out. You want to find out why. Use the steps of the scientific method to make a flowchart showing how you could test your hypothesis.
42. Writing in Chemistry One of your classmates states that chemistry is a pure science and that sciences such as biology exist only because of chemistry. What do you think about this statement? Write a paragraph explaining your answer and give reasons to support your opinion. 43. Antoine Lavoisier disproved a widely held belief in his time by using the scientific method. He proved that a substance called phlogiston did not exist. Find out what phlogiston was thought to be and how Lavoisier proved it did not exist. Present your findings in an oral report. 44. Choose an everyday occurrence and describe how you could use the scientific method to explain it. You can choose something as simple as why chlorine is added to drinking water or as complex as how a diesel engine operates. Make a bulletin board display that lists and describes each step.
40. Using what you know about the importance of chemistry in everyday life, write a help-wanted advertisement for each of the following careers in which you highlight the application of chemistry. a. b. c. d. e. f. g.
ecologist photographer archaeologist landscape architect computer-chip maker sports-equipment manufacturer geneticist