Chemical reactions

A chemical reaction is when to chemicals come into contact, and some type of reaction happens. To classify as a chemical reaction, a chemical change MUST occur. You start with one compound, and end up with another. For instance: iron (Fe) rusting, silver tarnishing, paper burning, these are all chemical reactions. For the rusting, when the iron comes into contact with the oxygen in the air (O2) and they combine, creating the rust. Reactions can include ions, molecules, or just pure atoms. Single reactions happen usually in a larger chain of reactions. Take, moving your arm. The contraction of your arm requires muscles, which require sugar, which have to be metabolized, which requires proteins...need a breather yet? Chemical reactions can take a lot more than just that. That sentence is smaller than a period in the sentence of other chemical reactions. There are infinitely many chemical reactions, each resulting in something totally different. Some chemical reactions with fire can change the color of fire. This is called the spectrum. Each element, or chemical has a different spectrum, but that's a whole different story.