Evaporation :

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• Evaporation is the process through which a liquid converts into its vapours below its boiling point.

• For the process of evaporation the substance requires energy (heat) which it takes from its surroundings.

• As a result the temperature of the surroundings decreases.

• It is a surface phenomenon.

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Evaporation causes cooling – earthen pot :

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• Water kept in an earthen pot cools automatically.

• The pot has pores in its body through which some amount of water seeps and comes out on the surface.

• When that water on the surface of the pot evaporates, it absorbs heat from the surroundings.

• As a result the water inside the earthen pot cools down.

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Experiment : Evaporation causes cooling :

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• Aim : To prove evaporation causes cooling

• Materials : An earthen pot, A metal pot, water

• Procedure :

1. Fill both the pots with water.

2. Let them remain undisturbed for about 2 hours.

• Observation : We observe that the water inside the earthen pot cools down whereas the water inside the metal pot remains hot.

• Conclusion : The earthen pot has pores on its body through which the water comes to surface, evaporates and cools the water. This is not the case with the metal pot.

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Evaporation causes cooling – Air cooler :

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• An air cooler uses the concept of evaporation to cool a room.

• The mechanism of the cooler sprinkles water on the cooling pads found on the backside surface of the cooler.

• The cooler then takes in hot air from the surroundings and passes it through the wet pad.

• The heat of the air is used by the water inside the cooling pad to evaporate, thereby cooling the air.

• This cool air is then blown into the room.