Which statement best describes the law of conservation of mass?

• A. The total number of molecules always increases in a chemical reaction.
• B. Mass is neither created nor destroyed during a chemical reaction.
• C. Atoms are converted into energy during chemical changes.
• D. Energy is always lost during a chemical reaction.

Answer: (B)

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 the number of molecules can change, but the total mass remains constant.
4. Realize that atoms are rearranged during chemical reactions, but they are not converted into energy or lost.
5. Conclude that the correct description is: Mass is neither created nor destroyed during a chemical reaction.