Which statement best describes the Law of Conservation of Mass?

• A. The total number of atoms changes during a chemical reaction.
• B. Chemical reactions can convert mass entirely into energy.
• C. Energy is always lost as heat in every chemical reaction.
• D. Mass is neither created nor destroyed during 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 must equal the total mass of the products.
3. Note that the number of atoms of each element remains constant throughout the reaction, although they may be rearranged to form new substances.
4. Eliminate options that suggest mass changes, such as atoms being created or destroyed, or mass converting entirely into energy, as these contradict the law.
5. Conclude that the best description is: 'Mass is neither created nor destroyed during a chemical reaction.'