Practice question · Multiple choice
Sweat cools you even on a hot day. At the molecular level, why does evaporation lower the temperature of the liquid left behind?
Hints
- Temperature is the average kinetic energy. Which molecules have enough energy to break free of the surface?
- Remove the top of a class’s exam scores and the class average falls, same arithmetic.
Show the answer
C. Only the fastest molecules escape, lowering the average
Why
Evaporation is selective emigration: only molecules in the high-energy tail can pay the escape cost, so the remaining population’s average, the temperature, drops. Humidity blocks the escape route, which is why muggy heat feels unbearable.
Practise States of matter and phase behaviour
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