The Atomic and Molecular Perspective of Chemistry

Chemistry is the study of the properties and behavior of matter. Matter is the physical material of the universe it is anything that has mass and occupies space. A property is any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types. This book, your body, the air you are breathing, and the clothes you are wearing are all samples of matter. Countless experiments have shown that the tremendous variety of matter in our world is due to combinations of only about 100 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 for 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 to both the kinds of atoms the matter contains (composition) and to the arrangements of these atoms (structure). 

Even apparently minor differences in the composition or structure of molecules can cause profound differences in properties. Ethanol, for example, is the alcohol in 

A FIGURE 1.1 Molecular models. The white, black, and red spheres represent atoms of hydrogen, carbon, and oxygen, respectively. 

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 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 and molecules. We make our observations in the macroscopic world, but in order to understand that world, we must visualize how atoms and molecules behave at the submicroscopic level. Chemistry is the science that seeks to understand the properties and behavior of matter by studying the properties and behavior of atoms and molecules. 

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