What does the law of conservation of mass state?

The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. This fundamental principle, first articulated by Antoine Lavoisier in the late 18th century, underlines that in a closed system, the total mass of reactants is equal to the total mass of products. Consequently, when a chemical reaction occurs, the atoms are rearranged to form new substances, but the overall mass remains constant throughout the process.

This concept is vital in chemistry as it reinforces the idea that the number of atoms remains constant before and after reactions, providing a basis for understanding stoichiometry and balancing chemical equations. It highlights the inherent stability and predictability in chemical reactions, which allows scientists to make quantitative predictions about reaction outcomes.