Which statement best describes the law of conservation of mass?

• A. The total number of atoms decreases during a chemical reaction.
• B. Matter can be converted entirely into energy in ordinary chemical reactions.
• C. Energy is always lost during a chemical reaction.
• D. Mass is neither created nor destroyed in a chemical reaction.

Answer: (D)

Verified step by step guidance

1. Understand that the law of conservation of mass states that in a chemical reaction, matter cannot be created or destroyed.
2. Recognize that this means the total mass of the reactants before the reaction must equal the total mass of the products after the reaction.
3. Note that the number of atoms remains constant because atoms are simply rearranged during the reaction, not lost or gained.
4. Realize that energy changes can occur during reactions, but these do not affect the total mass of the substances involved.
5. Therefore, the best description of the law of conservation of mass is: Mass is neither created nor destroyed in a chemical reaction.