For Class 8, 9 & 10
Foundation - a strong base in Physics, Chemistry, Maths & Biology
Concept-first questions with clear model answers across all four subjects, aligned to NCERT. Start early, build the habit, and walk into your board exams, NEET and JEE already ahead.
Showing 1 question in Chemistry for Class 9. Tap a card to reveal the answer.
ChemistryMatter in Our SurroundingsmediumWhy does evaporation cause cooling?
Reveal answer ↓
What it is
When the fastest particles escape a liquid's surface, the particles left behind are cooler.
Answer
During evaporation the fastest-moving (most energetic) particles at the surface of a liquid escape into the air. This lowers the average kinetic energy of the remaining particles, so the temperature of the liquid falls. The escaping particles also absorb latent heat from the surroundings, which is why evaporation produces a cooling effect - for example, sweating cools our body.
- •Fast (energetic) particles leave the surface
- •Remaining particles have lower average energy
- •Latent heat absorbed from surroundings
- •Example: sweating cools the body
Why learn this
It's why sweating, earthen pots (matka) and desert coolers keep things cold without a fridge.
💡 Memory trick
The 'hot-heads' leave first, so what's left behind is cooler.