The Law of Conservation of Mass asserts that in a closed system undergoing chemical reactions, matter is neither created nor destroyed, resulting in the equivalence between total reactant and product masses. Formally defined through stoichiometric balancing equations where atomic inventory remains invariant across reaction boundaries, this principle operates strictly within classical thermodynamics and theoretical chemistry. It establishes mass balance as a fundamental constraint for all non-nuclear chemical transformations, distinguishing itself from energy conservation which permits relativistic mass-energy interchange in high-energy contexts.
Prerequisite chain context: requires Balancing Chemical Equations for Synthesis Reactions.