Which of the following is a physical change?

• A. Dissolving sugar in water
• B. Burning sugar
• C. Rotting apple
• D. Fermenting

Answer: (A)

Distinguishing physical from chemical changes: a physical change keeps the substance’s identity the same, altering only how it appears or is arranged (like dissolving, melting, or breaking into pieces), without making a new substance. When sugar dissolves in water, the sugar molecules are still sugar and the water is still water; you just have a sugar–water solution. This process is typically reversible—evaporate the water and you can recover the sugar—so it’s a physical change.

Burning sugar involves a chemical reaction where bonds break and new substances form (like carbon dioxide, water, and energy). That changes what the material is, not just how it looks or where its pieces sit. Rotting and fermenting are also chemical changes because enzymes or microbes break down the original substances and produce new ones with different properties.