Which statement best describes the law of conservation of mass?

• A. Mass can be converted into energy in ordinary chemical reactions.
• B. The total number of atoms increases during a chemical reaction.
• C. Energy is always conserved during physical changes.
• 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 is neither created nor destroyed.
2. Recognize that this means the total mass of the reactants equals the total mass of the products.
3. Note that atoms are simply rearranged during a chemical reaction, so the total number of atoms remains constant.
4. Distinguish this from energy conservation, which is a separate principle related to energy changes, not mass.
5. Therefore, the best description is that mass is conserved in chemical reactions, meaning it is neither created nor destroyed.