What does the law of conservation of mass state?

The law of conservation of mass states that mass remains constant during a chemical reaction; it cannot be created or destroyed. This principle, established by Antoine Lavoisier in the late 18th century, emphasizes that the total mass of reactants before a reaction must equal the total mass of products after the reaction. Consequently, when substances undergo chemical changes, atoms are rearranged to form new compounds, but the total mass involved in the process does not change.

The other options misrepresent the law: the first option incorrectly implies that mass can be created or destroyed, which contradicts the fundamental principle. The third option suggests that mass is irrelevant in most reactions, which overlooks the fact that mass is a crucial aspect of reactants and products. Lastly, the fourth option limits conservation of mass to physical changes, disregarding its application in chemical changes where mass remains constant as well.