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25. Question: Why do we perspire before rains?

Answer: Before the rain falls, the atmosphere gets saturated with water

vapors as a result, the pro!ess of evaporation of sweat is delayed.

2". Question: Why does a thermometer #ept in boiling water show no

!hange in reading after $%%%&?

Answer: 'he boiling point of water is $%%%&. (n!e water starts boiling at this

temperature, thermometer re!ords no !hange in temperature. 'he )uantity

of heat supplied is being utili*ed as latent heat of evaporation to !onvert the

water at boiling point into vapour.

2+. Question: Why do we bring our hands !lose to the mouth while shouting

a!ross to someone far away?

Answer: By #eeping hands !lose to mouth the sound is not allowed to

spread -henomenon of dira!tion of sound/ in all dire!tion, but is dire!ted

to a parti!ular dire!tion and be!omes louder.

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