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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.

Class 824Class 924Class 1036
SubjectAllPhysics 19Chemistry 19Biology 19Mathematics 27
ChapterAllAtoms and MoleculesForce and Laws of MotionGravitationHeron's FormulaImprovement in Food ResourcesIs Matter Around Us PureLinear Equations in Two VariablesMatter in Our SurroundingsMotionNatural ResourcesNumber SystemsPolynomialsSoundStatisticsStructure of the AtomSurface Areas and VolumesThe Fundamental Unit of LifeTissuesWork and Energy

Showing 1 question for Class 9. Tap a card to reveal the answer.

ChemistryMatter in Our Surroundingsmedium

Why 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.