Q11 of 40 Page 1

Why does a desert cooler cool better on a hot dry day?

The outer walls of the cooler are constantly sprinkled by water. This water evaporates at a faster rate during the hot dry weather causing a cooling effect in the inside air of the cooler which is sent in the room through a fan.On a hot dry day, humidity is very low so the cooler works efficiently

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‘Osmosis is a special kind of diffusion’. Comment.

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Give reasons for the following observations: The smell of hot sizzling food reaches you several meters away but to get the smell from cold food, you have to go close.

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Give reasons for the following observations:

(a) Naphthalene balls disappear with time without leaving any solid.


(b) We can get the smell of perfume sitting several metres away.