The substances to the right of the arrow in a chemical equation are called the products, while those on the left side of the arrow are the reactants. The reactants are the substances present before the reaction starts, and the products are what is left at the end.
As matter cannot be created or destroyed, every atom in the reaction must also be present in the product in some form. There are many possible outcomes for a chemical reaction, depending on what elements and compounds are involved and their specific concentrations. The reaction can cause compounds to separate into elements or elements to join into new compounds. Compounds may also break apart and join together with other elements to form new compounds.