Final answer:
The law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction. The total mass of substances before a reaction is always equal to the total mass after a reaction. Option A is correct.
Step-by-step explanation:
The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. A. Matter is neither created nor destroyed. The total mass of substances before a reaction is always equal to the total mass after a reaction. Therefore, statement D. The total mass of substances before a reaction is greater than the total mass after a reaction is incorrect.
Based on the law of conservation of mass, the correct statement is A. Matter is neither created nor destroyed. This scientific principle, formulated by Antoine Lavoisier in 1789, applies to chemical reactions and asserts that the total mass of reactants equals the total mass of products resulting from the reaction. Therefore, during any chemical change, the matter is conserved, only changing form as atoms are rearranged, but not in quantity.