Which of the following statements best defines the law of conservation of mass?

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

Answer: (C)

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 atoms are simply rearranged during a chemical reaction, so the number of atoms remains constant, but they do not increase or decrease.
4. Distinguish this law from concepts related to energy conservation or matter-to-energy conversion, which are governed by different principles.
5. Conclude that the statement 'Mass is neither created nor destroyed in a chemical reaction' best defines the law of conservation of mass.