Explain the following Hot tea cool rapidly when poured into the saucer from the cup

cbse
thermal-properties

#1

Explain the following
(i) Hot tea cool rapidly when poured into the saucer from the cup.
(ii) Temperature of a hot liquid falls rapidly in the beginning but slowly afterwards.
(iii) A hot liquid cools faster if outer surface of the
container is blackened.


#2

(i) As surface area increases on pouring hot tea in saucer from the cup and the rate of loss of heat is directly proportional to surface area of the radiating surface, so the tea will cool faster in the saucer.
(ii) Temperature of a hot liquid falls exponentially in accordance with Newtons law of cooling. In other words, rate of cooling is directly proportional to the temperature difference between hot liquid and the surroundings. It is due to this reason that a hot liquid cools rapidly in the beginning but slowly afterwards.
(iii) When outer surface of container is blackened, the surface becomes good emitter of heat and so the hot liquid in it cools faster.