What is a hallmark of a physical change in matter?

• A. Energy transfer with a change of state, but no new substances formed.
• B. A chemical reaction producing new substances.
• C. A change in color only.
• D. The mass changing.

Answer: (A)

Physical changes change how matter exists without changing what the matter is chemically. When a substance changes state—like melting, freezing, or boiling—energy is transferred as heat or removed, and the particles rearrange into a different form, but the substance’s identity stays the same. That combination of energy transfer with a state change and no new substances formed is the hallmark of a physical change.

The other ideas point toward chemical changes. Producing entirely new substances isn’t a physical change. A change in color can happen for physical reasons in some cases, but it isn’t a definitive marker on its own. Mass changing isn’t expected in ordinary physical changes because mass is conserved in such processes.