You may have noticed that this assumes you know what solids, liquids, and gases are. Though most chemistry books define these terms early in the first section, I think you probably know enough to realize that if I were to throw something solid at your head, it would hurt. Likewise, if I throw a liquid at your head, you will get wet, and blowing air on you will cause you to feel a mild breeze.
However, if you've learned nothing else, you should be aware that chemistry doesn't just deal with macroscopic (big) properties of objects but also with microscopic (small) properties. As a result, it's not enough to know that hitting you in the head with a solid rock will hurt—we want to find out why the rock feels hard and how the atoms in the rock will feel about their impact with your head. In this section, we'll learn why rocks are hard, among other things.
Excerpted from The Complete Idiot's Guide to Chemistry © 2003 by Ian Guch. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.