This document provides an overview of chemical reactions, including: - A chemical reaction occurs when reactants are converted into products. - Lavoisier established the law of conservation of mass through experiments showing reactants and products have the same total mass. - Chemical equations represent reactions using formulas and can be balanced to show equal numbers of atoms on each side. - There are several types of chemical reactions including synthesis, decomposition, and oxidation-reduction. - Reactions can release or absorb energy in different forms like heat or light. Catalysts increase reaction rates without being used up.