What does the law of conservation of mass state regarding matter during a chemical reaction?

The law of conservation of mass states that matter cannot be created or destroyed during a chemical reaction. This fundamental principle indicates that the total mass of the reactants must equal the total mass of the products. Therefore, while substances may change forms and rearrange during a reaction, the total amount of matter remains constant throughout the process. This concept is foundational in chemistry as it ensures that any mass measured before a reaction must match the mass measured after the reaction has occurred, affirming that mass is conserved.

In the context of chemical reactions, this principle implies that atoms are simply rearranged rather than annihilated or generated anew. When balancing chemical equations, each side must have the same number of each type of atom, reflecting the conservation of mass in every reaction.