When two or more chemicals react to produce energy, the process is called a chemical reaction. During a chemical reaction, reactants undergo a transformation to form products, which can either absorb or release energy. Exothermic reactions release energy in the form of heat or light, while endothermic reactions absorb energy from their surroundings. These reactions are fundamental to various natural processes, such as combustion in engines, metabolism in living organisms, and many industrial applications. Understanding chemical reactions is crucial in fields like chemistry, biology, and environmental science.