Question

what happens when a substance undergoes a physical change?
○ some physical properties change, but the substance keeps its identity.
○ no physical properties change, and the substance keeps its identity.
○ some physical properties change, and the substance changes its identity.
○ no physical properties change, but the substance changes its identity.

Explanation:

To solve this, we recall the definition of a physical change. A physical change involves a change in physical properties (like shape, state, size) without altering the substance's chemical identity (i.e., the substance remains the same chemically).

• Option 1: "Some physical properties change, but the substance keeps its identity." matches the definition of physical change.
• Option 2: Says no physical properties change, which is wrong as physical changes do involve property changes (e.g., melting ice changes state).
• Option 3: Claims the substance changes its identity, but physical changes don't change the substance's chemical identity (that's a chemical change).
• Option 4: Is contradictory (no physical properties change but substance changes identity) and wrong.

Answer:

A. Some physical properties change, but the substance keeps its identity.