Answer
The central goal in chemistry is to understand the substances around us, and we do so by studying the atoms and molecules that make it up. The properties of matter are derived from their constituent parts. For example, carbon dioxide is comprised of 1 carbon atom and 2 oxygen atoms. Carbon monoxide is comprised of 1 carbon atom and 1 oxygen atom. Despite this small difference, carbon dioxide can be processed out of the body easily when it is in excess but carbon monoxide could easily prove fatal.
Work Step by Step
If you want to understand substances, you have to understand the atoms and molecules that comprise them.