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1. MATTER IN OUR SURROUNDINGS
medium
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.
Option A
Option B
Option C
Option D
Solution
$(a)$ Naphthalene is a substance which directly changes from solid to gas on heating by the process of sublimation. So, the naphthalene balls disappear with time as they sublime due to heat of surroundings.
$(b)$ The smell (aroma) of perfume reaches several meters away due to the fast diffusion of the gaseous perfume particles through the air.
Standard 9
Science
