Which statement describes a physical change?

• A. A new substance with different properties is formed.
• B. The substance changes state but composition remains the same.
• C. Energy is released during the change.
• D. The change cannot be reversed.

Answer: (B)

A physical change means the substance stays the same chemical substance, even though its form or state changes. The key idea is that no new substance is produced; the molecules are the same, just arranged differently or given more or less energy. When ice melts into liquid water, or when liquid water freezes into ice, you still have H2O. The composition hasn’t changed, only the state.

The other ideas describe changes that aren’t physical changes. Producing a new substance with different properties means a chemical change has occurred, because the substance’s identity has changed. Releasing energy can happen in both physical and chemical changes, so energy release by itself doesn’t define a physical change. And a change that cannot be reversed isn’t a defining feature of physical changes, since many physical changes (like melting and freezing) are reversible.