Distinguishing chemical from physical changes

Steps:

• Recall that chemical changes form new substances with different properties, while physical changes alter form without new substances.
• Evaluate each option: check if it involves breaking/reforming bonds (chemical) or just phase/state changes (physical).
• Identify rusting as oxidation, producing iron oxide—a new compound.
• Confirm others involve no new substances, ruling them out.

Why D is correct:

• Rusting of iron is a chemical change per the definition: it involves oxidation (4Fe + 3O₂ → 2Fe₂O₃), forming a new substance, iron(III) oxide.

Why the others are wrong:

• A: Distillation separates components by boiling point differences, a physical process with no new substances.
• B: Evaporation removes water physically, leaving unchanged sodium chloride.
• C: Melting wax changes solid to liquid state physically, without altering its chemical composition.

Final answer: D