Which of the following is an example of a physical change?

• A. Digestion of food
• B. Burning of magnesium ribbon
• C. Rusting of iron
• D. Melting of ice to form liquid water

Answer: (D)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: A physical change affects the form or state of a substance without changing its chemical composition, while a chemical change results in the formation of new substances with different chemical properties.
2. Analyze each option to determine if it involves a change in chemical composition or just a change in physical state:
3. 1. Digestion of food involves breaking down complex molecules into simpler ones, which is a chemical change.
4. 2. Burning of magnesium ribbon is a chemical change because magnesium reacts with oxygen to form magnesium oxide, a new substance.
5. 3. Rusting of iron is a chemical change where iron reacts with oxygen and moisture to form iron oxide (rust).
6. 4. Melting of ice to form liquid water is a physical change because it only changes the state of water from solid to liquid without altering its chemical identity.