Q1. Question 1 — Condensation
Why do water droplets appear on the outside of a glass containing ice-cold water?
The air around us always contains some water vapour.
When this air touches the cold outer surface of the glass, it loses energy and cools down.
On cooling, the water vapour changes into tiny liquid droplets — this change of state from gas to liquid is called condensation.
These droplets collect on the outside of the glass, which is why the glass looks wet.
Final Answer: Water vapour in the air condenses into droplets on cooling against the cold glass surface.
Common Mistake: Thinking the water has leaked out through the glass — glass is not porous.
Exam Tip: Use the word 'condensation' and mention water vapour present in the air.