What happens to the total mass of a substance when it undergoes a physical change?

• A. The total mass decreases.
• B. The total mass remains unchanged.
• C. The total mass becomes zero.
• D. The total mass increases.

Answer: (B)

Verified step by step guidance

1. Understand the definition of a physical change: it is a change in the state or appearance of a substance without altering its chemical composition.
2. 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.
3. Apply this law to a physical change, such as melting, freezing, or dissolving, where the substance's molecules remain the same and no mass is lost or gained.
4. Conclude that since the substance's chemical identity remains unchanged and no atoms are lost or gained, the total mass before and after the physical change must be the same.
5. Therefore, the total mass of a substance undergoing a physical change remains unchanged.