Question

(a) You want to wear your favourite shirt to a party, but the problem is that it is still wet after a wash. Mention three steps with reason that you will take to dry it faster.
(b) It is a hot summer day. Priyanshi and All are wearing cotton and nylon clothes respectively. Who do you think will be more comfortable and why ?
(c) During rainy season, we feel sticky and uncomfortable even under the fan. Why ?

CBSE Class IX Science LA (5 Marks)

Answer 1

(a) To dry it faster, rate of evaporation has to be increased, for this -

(1)  We can spread it to increase surface area.

(2)  We can iron it to increase the temperature.

(3)  We can increase the wind speed by spreading it under the fan.

(b)    Priyanshi will be more comfortable with cotton clothes, as in hot summer, cotton clothes will evaporate the sweat faster by taking latent heat of vaporization from the body and thus, making it comfortable by taking away body's heat faster.

During rainy season, humidity is high and rate of evaporation is slower. Thus, we feel sticky.

Answer 2

condition that can increase the rate of evapourisation of water are :

(a) An increase in the surface area by spreading the shirt.

(b) An increase in the temperature by putting the shirt under the sun .

(c) Increase in the wind speed by spreading it under the fan.