Chapter 1

NCERT
Class 9
Science
Solutions
3. Write the reasons for the following observations. (a) Naphthalene disappears with time without leaving any solid. (b) The smell of perfume reaches us even after sitting far away.

Question:

Write the reasons for the following observations.

(a) Naphthalene disappears with time without leaving any solid.

(b) The smell of perfume reaches us even after sitting far away.

Answer:

(a) Naphthalene (or phenyl) is a sublimation substance which disappears with time without leaving any solid, because due to sublimation they mixed with air and blows. It means Naphthalene get converted into Gaseous phase without converting into liquid phase.

(b) Perfume gets automatically changed into vapour at normal or room temperature. So it’s particles automatically spread out all around mixing with air particles. That is, their particles are diffused very quickly in air. So, the person sitting far away also sense its smell.

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