Give reason for the following observations:

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

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

(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.

Sublimation is the transition of a substance directly from the solid state to the gaseous state, without passing through the liquid state.

(b) We can get the smell of perfume while sitting several metres away because perfume contain volatile solvents which when released into air gets converted to gaseous state and then diffuses in air.

As we know that gases diffuse faster, so the gaseous particles of perfume diffuses with a faster rate in air and thus it reaches more distance within few seconds.