Which statement best describes the law of conservation of mass?

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

Answer: (B)

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 must equal the total mass of the products.
3. Note that this law implies the number of atoms remains constant during a chemical reaction, although they may be rearranged.
4. Distinguish this from energy conservation, which is a separate principle related to physical and chemical changes.
5. Conclude that the correct description of the law of conservation of mass is: 'Mass is neither created nor destroyed in a chemical reaction.'