Question

Give reason for the following-

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

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

c) Desert cooler cools better on a hot dry day​

Answer 1

Answer:

(a) Naphthalene balls disappear with time without leaving any solid because they undergo sublimation at standard room temperature where they directly get converted from solid state to a gaseous state without passing through the liquid state.

(b) When perfume is released from the bottle it quickly changes into a vapor. The perfume vapor moves rapidly in all directions as it is volatile. The kinetic energy of the gas molecules is high and the rate of diffusion is high. Hence, we can get the smell of perfume sitting several meters away.

(c) Evaporation depends on the amount of water vapour present in air (humidity). ... On a hot dry day, the amount of water vapour present in air is less. Thus, water present inside the desert cooler evaporates more, thereby cooling the surroundings more. That is why a desert cooler cools better on a hot dry day.

I hope this helps you