1.1 The Study of Chemistry

Before traveling to an unfamiliar city, you might look at a map to get some sense of where you are heading. Chemistry may be unfamiliar to you, too, so it's useful to get a general idea of what lies ahead before you embark on your journey. In fact, you might even ask why you are taking the trip.

The Molecular Perspective of Chemistry

Chemistry involves studying the properties and behavior of matter. Matter is the physical material of the universe; it is anything that has mass and occupies space. This book, your body, the clothes you are wearing, and the air you are breathing are all samples of matter. Not all forms of matter are so common or so familiar, but countless experiments have shown that the tremendous variety of matter in our world is due to combinations of only about 100 very basic or elementary substances called elements. As we proceed through this text, we will seek to relate the properties of matter to its composition, that is, to the particular elements it contains.

Chemistry also provides a background to understanding the properties of matter in terms of atoms, the almost infinitesimally small building blocks of matter. Each element is composed of a unique kind of atom. We will see that the properties of matter relate not only to the kinds of atoms it contains (composition), but also to the arrangements of these atoms (structure).

Atoms can combine to form molecules in which two or more atoms are joined together in specific shapes. Throughout this text you will see molecules represented using colored spheres to show how their component atoms connect to each other (Figure 1.1). The color merely provides a convenient way to distinguish between the atoms of different elements. Molecules of ethanol and ethylene glycol, which are depicted in Figure 1.1, differ somewhat in composition. Ethanol contains one red sphere, which represents an oxygen atom, whereas ethylene glycol contains two.

Figure 1.1 Molecular models. The white, dark gray, and red spheres represent atoms of hydrogen, carbon, and oxygen, respectively.

Even apparently minor differences in the composition or structure of molecules can cause profound differences in their properties. Ethanol, also called grain alcohol, is the alcohol in beverages such as beer and wine. Ethylene glycol, on the other hand, is a viscous liquid used as automobile antifreeze. The properties of these two substances differ in a great number of ways, including the temperatures at which they freeze and boil. One of the challenges that chemists undertake is to alter molecules in a controlled way, creating new substances with different properties.

Every change in the observable world—from boiling water to the changes that occur as our bodies combat invading viruses—has its basis in the unobservable world of atoms and molecules. Thus, as we proceed with our study of chemistry, we will find ourselves thinking in two realms, the macroscopic realm of ordinary-sized objects (macro large) and the submicroscopic realm of atoms. We make our observations in the macroscopic world with our everyday senses—in the laboratory and in our surroundings. In order to understand that world, however, we must visualize how atoms behave.

Why Study Chemistry?

Chemistry provides important understanding of our world and how it works. It is an extremely practical science that greatly impacts our daily living. Indeed, chemistry lies near the heart of many matters of public concern: improvement of health care, conservation of natural resources, protection of the environment, and provision of our everyday needs for food, clothing, and shelter. Using chemistry, we have discovered pharmaceutical chemicals that enhance our health and prolong our lives. We have increased food production through the development of fertilizers and pesticides. We have developed plastics and other materials that are used in almost every facet of our lives. Unfortunately, some chemicals also have the potential to harm our health or the environment. It is in our best interest as educated citizens and consumers to understand the profound effects, both positive and negative, that chemicals have on our lives and to strike an informed balance about their uses.

Most of you are studying chemistry, however, not merely to satisfy your curiosity or to become more informed consumers or citizens, but because it is an essential part of your curriculum. Your major might be biology, engineering, agriculture, geology, or some other field. Why do so many diverse subjects share an essential tie to chemistry? The answer is that chemistry, by its very nature, is the central science. Our interactions with the material world raise basic questions about the materials around us. What are their compositions and properties? How do they interact with us and our environment? How, why, and when do they undergo change? These questions are important whether the material is part of high-tech computer chips, an aged pigment used by a Renaissance painter, or the DNA that transmits genetic information in our bodies (Figure 1.2). Chemistry provides answers to these and countless other questions.

Figure 1.2 (a) A microscopic view of a computer chip. (b) A Renaissance painting, Young Girl Reading, by Vittore Carpaccio (1472–1526). (c) A long strand of DNA that has spilled out of the damaged cell wall of a bacterium.

By studying chemistry, you will learn to use the powerful language and ideas that have evolved to describe and understand matter. The language of chemistry is a universal scientific language that is widely used in other disciplines. Furthermore, an understanding of the behavior of atoms and molecules provides powerful insights in other areas of modern science, technology, and engineering. For this reason, chemistry will probably play a significant role in your future. You will be better prepared for the future if you increase your understanding of chemical principles, and it is our goal to help you achieve this end.