NCERT Solutions for Class 5th The World Around Us Chapter 1 Ice cubes in a steel glass — Activity 2
Book page 6 Updated on2026-09-19
Q1.
Take a steel glass. Put some ice cubes in it. Observe the small water droplets forming on the glass. (a) Where do these water droplets come from?
Answer
They come from the air around the glass. The air holds water vapour that we cannot see. The cold glass cools that vapour, and it turns back into tiny drops of water on the outside of the glass.
Do it step by step and watch.
Take a dry steel glass. Wipe it and check — the outside is dry.
Put four or five ice cubes in it.
Wait for two minutes. Do not touch it.
Now look at the outside of the glass. It is covered with tiny water drops. Touch it — your finger gets wet.
Invisible water vapour touches the cold glass, cools, and becomes drops you can see.
Why it happens: Warm air can hold water vapour. Cold air cannot hold as much. When the warm air of the room touches the very cold steel, it cools at once, and the vapour it was carrying turns back into liquid water. This changing of vapour into water is called condensation.
Check it yourself: Keep a second glass beside it with ordinary room-temperature water in it. That glass stays dry outside. Only the cold glass gets wet — so the drops must be coming from the air, not leaking through the steel.
Q2.
(b) What happens to the ice cubes after they are left in the glass for some time?
Answer
The ice cubes melt. They slowly change into liquid water, and after some time the glass has water in it instead of ice.
What you will see, in order:
First the sharp corners of the cubes become round and smooth.
Then the cubes get smaller and a little water collects at the bottom.
The cubes float in this water and keep shrinking.
In the end there is no ice left — only cold water.
Ice (solid) + heat from the room → Water (liquid)
Why it happens: The room is warmer than the ice. Heat always moves from the warmer thing to the colder thing. So heat from the air and from the glass goes into the ice. That heat makes the ice melt — it changes from the solid form to the liquid form. It is still the same water; only its form has changed.
Try this: Put one ice cube in a plate in the shade and one in the sunlight. The one in the sunlight melts much faster, because it gets heat more quickly.
Q3.
(c) If we heat water, what will happen to it?
Answer
The water becomes hot, then it starts to boil, and it changes into steam — that is, into water vapour. The water in the pan slowly gets less and less.
Watch a pan of water on the stove.
The water gets warm, then hot.
Small bubbles begin to rise from the bottom.
Soon the water bubbles fast all over. This is boiling.
A white misty cloud rises above the pan. That is steam — water vapour that has cooled a little in the air.
If you keep the stove on, the water level in the pan goes down, because more and more water is leaving as vapour.
Water (liquid) + heat → Water vapour (gas)
Why it happens: Heat gives the water enough energy to leave the pan and float away in the air as a gas. Water does not need to boil to do this — wet clothes dry in the sun in the same way, only much more slowly. Boiling is simply very fast evaporation.
A safety note: Steam is much hotter than boiling water and can burn badly. Watch a boiling pan from a distance, and only with an adult nearby.
Q4.
In the above activity, what forms of water do you see?
Answer
All three forms of water — solid, liquid and vapour.
Form
Where you see it in this activity
What changed
Solid
The ice cubes put into the steel glass
Water frozen hard
Liquid
The melted water inside the glass, and the drops on the outside
Ice melted; vapour condensed
Vapour (gas)
The invisible water in the air that made the drops; the steam above the boiling pan
Water heated and rose as gas
Solid ⇄ Liquid ⇄ Vapour Heat pushes it to the right. Cooling brings it back to the left.
Why this matters: This one small activity shows the whole idea of the chapter. Water can change its form and change back again. Nature does exactly the same thing on a huge scale, and we call it the water cycle.