ICSE Class 8 Physics Question 8 of 14

Matter — Question 10

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Question 10

Explain with an example that when a liquid evaporates, it takes heat from its surroundings.

Answer

If some alcohol (or spirit) is poured on some cotton (or wool) wrapped around the bulb of a thermometer, the reading of the thermometer falls. The reason for this observation is that, to evaporate, alcohol requires heat which it absorbs from the cotton wrapped around the thermometer (it's surroundings) producing a cooling effect that is recorded by the thermometer as a fall in temperature.