Which of the following changes would be considered a physical change?

Which of the following changes would be considered a physical change?

• A. Iron rusting
• B. Bread baking
• C. Digesting food
• D. Melting ice

Answer: (D)

Melting ice is a physical change because it changes only the form (from solid to liquid) without creating a new substance. The material remains water (H2O), just in a different state, and this change is reversible—ice can refreeze back into ice. The other scenarios involve chemical changes. Iron rusting forms a new substance (iron oxide) through a chemical reaction with oxygen. Bread baking involves chemical reactions that alter the substances in the dough. Digesting food breaks molecules into smaller units, creating new substances that your body can use. So those are chemical changes, unlike melting ice.

Melting ice is a physical change because it changes only the form (from solid to liquid) without creating a new substance. The material remains water (H2O), just in a different state, and this change is reversible—ice can refreeze back into ice.

The other scenarios involve chemical changes. Iron rusting forms a new substance (iron oxide) through a chemical reaction with oxygen. Bread baking involves chemical reactions that alter the substances in the dough. Digesting food breaks molecules into smaller units, creating new substances that your body can use. So those are chemical changes, unlike melting ice.