EN हिं

NCERT Solutions Curiosity Chapter 7 Think like a scientist — How Particles Move in Different States of Matter?

Book page 110 Updated on2026-09-05

Q1.
Watch carefully and compare. What do you observe?
Answer

The same grain of potassium permanganate spreads at three clearly different speeds, and the order is always the same.

TumblerSpeed of spreadingMotion of the water particles
Hot waterFastestWater particles move faster
Water at room temperatureLess quickSlower than in hot water
Ice-cold waterSlowestSlower still

The three tumblers differ in only one thing — their temperature — so the temperature must be what is causing the difference.

The conclusion: the movement of particles increases when heat is provided. Faster water particles pull the potassium permanganate particles out of the grain more quickly and knock them further in the same time, so the colour reaches every part of the hot tumbler first.
Keep the test fair: use tumblers of the same size, the same amount of water in each, and grains of about the same size, dropped in at the same moment. Then temperature is the only thing that varies, and the comparison means something.
Q2.
Try to depict it by drawing a diagram.
Answer

A good diagram here must show three tumblers side by side at one instant of time, so that the comparison is visible at a glance. Draw and label:

  • the three tumblers, marked hot water, water at room temperature and ice-cold water;
  • the grain of potassium permanganate at the bottom of each;
  • the pink colour spread over a large part of the hot tumbler, a middling part of the room-temperature one, and only a small region around the grain in the ice-cold one;
  • a short arrow near a few particles to show that they are moving — longest arrows in the hot tumbler.

Here is one way to draw it:

Hot water spreads fastest Room temperature spreads less quickly Ice-cold water spreads slowest The same grain, the same length of time
Purple bar = the grain of potassium permanganate; pink dots = its particles after the same interval. The hotter the water, the faster its particles move, and the further the colour has travelled.
Label the diagram honestly: the pink dots stand for particles far too small to be seen. A diagram of the particle model is always a picture of an idea, drawn hugely enlarged — never a photograph of what the eye sees.
Was this helpful? Report an error