A chemical reaction is the process of rearranging atoms between substances to form new compounds with different properties. When compounds or elements react, they are transformed into one or more different substances.
The substances that react are called reactants and the substances that are generated are called products. The chemical reaction is represented by a chemical equation, where the reactants are placed to the left of an arrow followed by the products to the right.
We can tell that a reaction is taking place because we see a change in the environment: