What does the law of conservation of mass state?

The law of conservation of mass states that in a closed system, the mass of the reactants must equal the mass of the products in a chemical reaction. This principle indicates that atoms are neither created nor destroyed during chemical changes; instead, they are simply rearranged to form new substances. Therefore, the total mass remains constant throughout the reaction.

This law is fundamental to understanding chemical reactions, as it implies that all atoms in the reactants are accounted for in the products. For instance, when hydrogen and oxygen react to form water, the total mass of hydrogen and oxygen before the reaction equals the total mass of water produced, illustrating that mass is conserved in the process.

The other responses suggest scenarios where mass can either be created or destroyed, which contradicts the fundamental principle of conservation of mass established by scientists like Antoine Lavoisier in the 18th century. Thus, the correct statement clearly adheres to the established law.