NCERT Solutions Curiosity Chapter 7 In-text Questions — How Does the Interparticle Spacing Differ in the Three States of Matter?
Book page 107 Updated on2026-09-05
Q1.
What role does the interparticle spacing play in determining the properties of each state (solid, liquid, and gas)?
Answer
The spacing decides everything, because the spacing is the interparticle distance — and the strength of the attraction depends on that distance, falling off drastically as it grows.
So one quantity controls two things at once: how strongly the particles are held, and how freely they can move. Together these fix the shape, the volume and the compressibility of the substance.
Fig. 7.12 redrawn: spacing is minimum in a solid, a little more in a liquid, and maximum in a gas. The gaps hold nothing at all — not even air.
State
Interparticle spacing
Attraction that follows
Properties that follow
Solid
Minimum
Maximum
Fixed shape and volume; particles only vibrate; practically incompressible
Liquid
A little more than in solids
Slightly weaker than in solids
Fixed volume, no fixed shape; particles move within a limited space; practically incompressible
Gas
Maximum
Minimum (negligible)
Neither shape nor volume fixed; particles move through all the available space; easily compressed
One warning the chapter gives: you might assume the space between particles is filled with air. It is not. It contains nothing at all.
Q2.
What can we say about the behaviour of gas in the syringe?
Answer
That a gas is compressible — its particles can be forced much closer together — and that it springs back on its own when released.
Your thumb seals the open end, so not one particle of air can escape. Yet the plunger still moves in and the volume of air inside decreases. The only way the same quantity of air can occupy less room is if there was a great deal of empty space between its particles to begin with, and the external pressure of your push has reduced that space.
Stop pushing and the particles, which move freely in all directions, spread out again and the plunger returns to its original position.
Now repeat it with water: the plunger will hardly move — water is practically incompressible. The contrast is the point of the activity. Gas particles have a lot of room between them; liquid particles have very little.