This document defines key terms related to chemical equations, including reactants, products, coefficients, and subscripts. It explains that a chemical equation represents a chemical change and must obey the law of conservation of mass, meaning the same number and type of atoms go into and come out of the reaction. Balancing chemical equations involves adjusting coefficients so that the same number of each type of atom appears on both sides. Some tips for balancing include starting with larger formulas and treating polyatomic ions as single units. Examples of balancing different equations are provided.