NCERT Solutions Curiosity Chapter 7 In-text Questions — What Decides Different States of Matter?
Book page 101 Updated on2026-09-05
Q1.
But, where did the sugar go?
Answer
Into the spaces between the water particles.
When sugar dissolves, its tiny particles separate from one another and occupy the space that is already available between the particles of water. Those gaps have a name: interparticle spaces.
Two separate observations point to the same answer:
Taste (Activity 7.2): the whole solution is sweet, so the sugar particles are spread all through the water.
Volume (Activity 7.7): when the sugar dissolves, the level drops from mark B down to mark C. The solution takes up less room than the water and the sugar did separately — which can only happen if the sugar has moved into space that was already there.
Why the level falls below mark B: the dissolved particles do not need fresh room of their own — they occupy space that already existed between the water particles, so the volume of the solution is less than the volume of the water plus the volume of the sugar.
Q2.
Chalk and sugar can both be broken down into their constituent particles. But how are the constituent particles held together to form the solid pieces we see?
Answer
By forces of attraction between the particles themselves, called interparticle attractions.
The chapter tells you three things about these forces, and each one matters:
They are attractive in nature — they pull the particles towards one another and so hold a piece of chalk together as one object.
Their strength depends on the nature of the substance and on the interparticle distance. Even a slight increase in that distance decreases the force drastically.
Their strength ultimately decides the physical state of the substance — solid, liquid or gas.
In solid chalk and solid sugar these forces are strong enough to hold every particle in a fixed position. That is why a stick of chalk has a definite shape and volume, and why it must be broken by force rather than simply poured.
Look ahead: this one sentence — the force falls off drastically as the distance grows — explains the rest of the chapter. Heat the solid, the particles move a little further apart, the force collapses, and the solid melts.