According to the Law of Conservation of Mass, what is conserved during physical changes?

• A. Mass
• B. Volume
• C. Number of molecules
• D. Energy

Answer: (A)

Verified step by step guidance

1. Recall the Law of Conservation of Mass, which states that mass cannot be created or destroyed in a closed system during a chemical or physical change.
2. Understand that during physical changes (such as melting, freezing, or dissolving), the substance's physical form may change but its chemical identity remains the same.
3. Recognize that because the chemical identity does not change, the total mass of the substance before and after the physical change remains constant.
4. Note that volume can change due to changes in state or pressure, and the number of molecules can remain the same but is not the conserved quantity emphasized by the law.
5. Conclude that the Law of Conservation of Mass specifically refers to the conservation of mass during physical changes.