Question

Give reasons for the following observations :-

a) Napthalene balls disappear with time without leaving and solid .

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

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Answer 1

• Answer: (a): Naphthalene balls disappear with time without leaving any solid because they undergo sublimation i.e., they directly change into vapour without passing through the liquid state. (b): We can get the smell of perfume sitting several metres away due to diffusion.

Answer 2

Answer:

Naphthalene balls disappear with time without leaving any solid, because naphthalene balls sublime and directly changes into vapour state without leaving any solid.

2.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.