Atoms are the building blocks of our world — tiny units that make up everything around us. In the same way that wheels, bands, screws, and pins fit together to make a clock or a toy, atoms of various kinds fit together to form the substances around us.
At one time or another, almost everyone has taken apart a toy or a clock to see what makes it work. The result is simply a collection of parts. Some people can figure out how to put the parts together again, to rebuild the toy or clock. And a few people can even work out ways to make entirely new devices out of the toy or clock parts.
Modern scientists have learned to do very much the same kind of thing with matter. Matter is anything that takes up space and has weight. Air, water, rock, and even people are composed of matter. All matter can be split into smaller and smaller pieces. There is a limit, however, to how small the pieces can be. A molecule is the smallest piece that keeps the characteristics of the original substance. For instance, a sugar molecule is the smallest piece that is still like sugar.
With special equipment a molecule can be broken down into still smaller parts. These are atoms. From this example, we can see why atoms are called the building blocks of matter. All the kinds of matter in the world are made from only about 100 different kinds of atoms.
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