Question

Give a reason for the following observations: (a) Naphthalene balls disappear with time without leaving any solid residue (b) We can get the smell of perfumes sitting several miles away.

Answer 1

Hint: Sublimation is the physical process of conversion of the solid phase directly into vapour phase without being converted into the liquid phase. Gaseous particles are loosely held together and can travel far.

Complete step by step answer:
a. When naphthalene balls are left in clothes, they slowly start to disappear into the vapour phase without leaving any trace of the solid and this is due to the fact that naphthalene is sublime, i.e, it gets converted directly into the vapour state from the solid state without the liquid state being involved in the middle. The main reason behind this being the fact that the entropy of the sublimable substances are much higher for the gaseous gas as compared to the liquid state. Hence, they prefer to directly convert to the gaseous state.

b. We can get the smell of perfumes sitting several miles away, this is because of the fact that the molecules of the perfume diffuse in the air and can travel some distance till the concentration of the perfume molecules are the same throughout.

Note:
Diffusion is the phenomenon of movement of the molecules from the area of higher concentration to the area of lower concentration. Diffusion can be seen mainly in liquids and gases because particles move freely from one place to another. Diffusion is an important process for all the living things.