Which of the following is a physical change?

• A. Shredding paper
• B. Burning wood
• C. Rusting iron
• D. Digestion of food

Answer: (A)

A physical change happens when a material changes form or appearance but keeps its chemical identity. Shredding paper fits this because the paper is still paper with the same chemical composition; it’s just in smaller pieces, and no new substance is created.

Burning wood is a chemical change because it involves a chemical reaction with oxygen that creates new substances like ash, smoke, carbon dioxide, and water vapor. Rusting iron is chemical too, as iron reacts with oxygen to form iron oxide. Digestion of food is primarily chemical change in the body, where enzymes break down molecules and form different ones, even though there may be some mechanical chewing involved.