Chemistry is the science dealing with the composition of matter and the transformations of matter.
Recall that matter is composed of different substances that are called elements . An element is something that cannot be broken down into other simpler substances, while retaining the unique chemical properties. The smallest indivisible unit of an element is called an atom . A 100 million atoms lined up from end to end would equal about 1 inch. Atoms in turn are composed of subatomic particles .