According to the Law of Conservation of Mass, what happens to the total mass of substances during a physical change?

• A. The total mass remains unchanged.
• B. The total mass decreases.
• C. The total mass fluctuates unpredictably.
• D. The total mass increases.

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 any physical or chemical process.
2. Understand that a physical change involves changes in the state or appearance of a substance without altering its chemical composition (e.g., melting, freezing, dissolving).
3. Since no atoms are lost or gained during a physical change, the total number of atoms—and therefore the total mass—remains constant.
4. Express this concept mathematically as: \(\text{Mass}_{\text{initial}} = \text{Mass}_{\text{final}}\) during a physical change.
5. Conclude that the total mass of substances remains unchanged during a physical change, consistent with the Law of Conservation of Mass.