CHAPTER 1 CHEMISTRY DEFINED NN he science of chemistry is the study of matter and the chemical changes J that matter undergoes Research in chemistry not only answers basic ques tions about nature but also affects people's lives Chemistry has been used for exam ple to make stronger metals to enrich soil for growing crops to destroy harmful bacteria and to measure levels of pollution in the environment It has also made pos sible the development of plastics synthetic fibers and new medicines Products produced by the chemical industry are an ordinary part of our daily lives The chemical industry converts raw materials such as water salt metals and minerals petroleum coal natural gas plant cellulose and starch and atmospheric gases into other products Some products require much more processing than others before they are subsequently used by manufactur ers and other industries Manufacturers use chemical products to make metal and 12
CHEMISTRY DEFINED A chemical company s researcher conducts experiments to recover traces of precious metals that are contained in the industrial water that was used during the recycling of electronics Marc Preel AFP Getty Images paper products wallboard pipe insulation and other construction materials polymers for electronic devices bottles films paints and other items and fibers for carpets and fabrics A few examples of other chemical products that are used by consumers include medicines dyes paints fertilizers shampoos detergents waxes perfumes cosmetics and flavorings 13
CHEMISTRY UNDERSTANDING SUBSTANCE AND MATTER The work of chemistry is generally described as analysis and synthesis Chemists analyze substances by breaking them down to find out what they are made of Chemists syn thesize substances by putting them together in different possibly more useful combina tions Assisted by specialized instruments and computers chemists study materials as small as single atoms and as large and complex as DNA deoxyribonucleic acid which contains millions of atoms USING CHEMICAL ANALYSIS Do a criminal suspect's hands show traces of gunpowder Is the blood sugar level of a person with diabetes under control Will sulfur and other pollutants be released into the air when a shipment of coal is burned in a power plant Chemical analysis answers these and many other questions by providing a way to deter mine the nature of any substance in terms of the elements or compounds that it contains There are two main approaches to chemical analysis Qualitative analysis shows which ele ments or groupings of elements are present in a sample Quantitative analysis measures how 14
CHEMISTRY DEFINED much of each constituent is present A com plete analysis of a substance often requires a combination of these methods Scientists first seek to determine whether a sample is organic or inorganic Organic compounds contain the element carbon whereas inorganic compounds generally do not contain carbon One way to distinguish organic and inorganic compounds is by observing the way they behave when they are heated in air Organic compounds usu ally melt and then burn with a flame that can be smoky sometimes leaving a black res idue of carbon Both organic and inorganic compounds are subjected to various tests to determine their makeup In the course of the 20th and early 21st centuries analytical methods evolved con siderably Although traditional methods are still used most analysis now involves the use of increasingly sophisticated instruments The older classical methods rely on chemi cal reactions to perform an analysis Newer instrumental methods typically depend on only the measurement of a physical prop erty of a sample such as a solution's ability to conduct electricity In some classical meth ods the results of a chemical reaction need 15
