Evaporation
Physics: Cambridge International GCSE Supplement, topic 2.2.9
Evaporation
Evaporation describes a liquid changing state into a gas without boiling.
Evaporation
- In a liquid, different particles (e.g molecules) can travel at different speeds.
- The molecules moving fastest have the most energy, they may have enough energy to escape from the surface of the liquid and enter the gas above.
Evaporative cooling
- The higher the temperature of a liquid, the higher the kinetic energy of the liquid's molecules.
- If the molecules with the most energy leave a liquid, then the molecules left in the liquid will have a lower average energy and a lower average temperature (cooling the liquid).
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Evaporation is not boiling
- Evaporation can happen at any temperature.
- Evaporation only happens at the surface of a liquid (boiling happens everywhere in a liquid).
- Boiling needs extra energy to be transferred to the liquid, but evaporation doesn’t.
Test yourself on Evaporation
A student says that evaporation and boiling are the same, as both processes involve converting liquid into gas. Is the student correct?