Question

Question 3. Give reason for the following observations.
(a) Naphthalene balls disappear with time without leaving any solid.
(b) We can get the smell of perfume sitting several metres away.
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Answer 1

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(a) Naphthalene balls undergo sublimation due to which it converts directly into vapours and disappear into air without leaving any solid.

(a) Naphthalene balls undergo sublimation due to which it converts directly into vapours and disappear into air without leaving any solid.(b) The particles of perfume diffuse rapidly into the air and its smell can be felt while sitting several metres away.

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Answer 2

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) When perfume is released it quickly changes into vapour. The kinetic energy of gas molecules is high & the rate of diffusion is high. Hence we can smell the perfume sitting several metres away.