Question:
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.
Answer:
- a) Naphthalene balls undergo sublimation, which is transition from solid state to the vapour state directly, bypassing the liquid state. Due to this phenomenon the naphthalene ball is seen to disappear with time.
- b) Perfume can be smelled sitting several metres away due to the phenomenon called as diffusion. The perfume spray vaporises and starts to mingle with the air molecules in a directional manner through the air, that is it starts to move away from the site of origin. Due to this it reaches several metres away.
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