The term for the law of conservation of mass in chemistry is known as the "law of conservation of mass." This principle states that mass cannot be created or destroyed in a closed system during a chemical reaction. Instead, the mass of the reactants must equal the mass of the products. This concept was formulated by Antoine Lavoisier in the late 18th century and laid the foundation for modern chemistry. It emphasizes the importance of understanding the amounts of substances involved in reactions and supports the idea of balanced chemical equations.