Which event is a chemical change?

• A. Melting ice
• B. Dissolving sugar in water
• C. Tearing paper
• D. Burning wood to ash

Answer: (D)

Chemical changes involve breaking and forming bonds to create substances with new composition and properties. Burning wood to ash does just that: the wood reacts with oxygen in a combustion process, turning into carbon dioxide, water vapor, and solid ash, with energy released. The original materials are transformed into new substances, and this change is typically irreversible under ordinary conditions.

Melting ice changes only the state from solid to liquid; the substance remains water, so no new chemical species form. Dissolving sugar in water is a physical process where sugar and water intermingle, but their chemical identities don’t change. Tearing paper is also physical, simply breaking it into pieces without altering its chemical composition.

So, burning wood to ash is the event that shows a chemical change.