An increase in entropy can best be illustrated by

Correct answer: mixing of gases.

Explanation: Entropy measures disorder/randomness. When two gases mix, the particles spread out and become more randomly distributed, so entropy increases.

• Freezing of water – Decreases entropy (liquid → more ordered solid).
• Condensation of vapour – Decreases entropy (gas → liquid, less random).
• Solidifying candle wax – Decreases entropy (liquid → solid).