NCERT Solutions for Class 5th The World Around Us Chapter 1 Water Cycle in a sealed bag — Activity 3
Book page 7 Updated on2026-09-19
Q1.
Take a transparent bag. Use a marker to draw the sun, clouds, trees and arrows on it as shown in the picture. Fill one-third of it with coloured water. Seal the bag tightly to prevent any leaks. Place it in the sunlight. After a few hours, observe the changes inside the bag.The picture beside Activity 3 on page 7 — the sealed bag with the sun, clouds, tree and arrows drawn on it with a marker, and coloured water filling the lower third.
Answer
What you will see: the water in the bag becomes warm; tiny drops appear on the inside of the empty upper part of the bag; the drops grow bigger, join together, slide down the sides and fall back into the coloured water. The bag is sealed, so no water is lost — the same water keeps going round.
How to do it:
Take a clear zip-lock bag.
With a marker, draw a sun in one top corner, a cloud beside it, a tree at the bottom, and arrows going up on one side and down on the other.
Add a few drops of blue paint or food colour to about one cup of water. The colour makes the water easy to see.
Fill the bag one-third full with this coloured water.
Press out the air and seal the bag tightly. Check for leaks by turning it over once.
Stick it on a sunny window with tape, with the water at the bottom.
Come back after three or four hours and look closely at the top half of the bag.
Time
What you will see
After 1 hour
The bag feels warm. The upper part looks slightly misty.
After 2–3 hours
Many tiny clear drops sit on the inside of the upper part of the bag.
After 4 hours
Some drops have joined into bigger drops. They slide down and drop back into the coloured water.
Level of the coloured water
Almost the same as at the start — nothing escaped from the sealed bag.
Why it happens: Sunlight heats the coloured water. Some of it evaporates — it turns into water vapour and rises into the empty part of the bag. The plastic at the top is cooler than the water, so when the vapour touches it, it condenses into tiny drops. When the drops become heavy they run down. That is exactly evaporation, condensation and rain, happening inside a bag you can hold.
Notice one thing: the drops on the plastic are clear, not blue. The colour stayed behind in the water. In the same way, the salt of the ocean stays behind and the rain that falls is fresh.
Q2.
Complete the table: I Observe — I Wonder — It is because of… (first row given: Water heats up / How does water heat up? / Sunlight; second row given: Water droplets formed inside the cover)
I Observe
I Wonder
It is because of…
Water heats up
How does water heat up?
Sunlight
Water droplets formed inside the cover
The table printed with Activity 3 on page 7, exactly as it stands in the book — the first row is filled in for you, and the rest is left blank.
Answer
Here is the completed table. The first row is the book's example; the rest are filled from what actually happens in the bag.
I Observe
I Wonder
It is because of…
Water heats up
How does water heat up?
Sunlight
Water droplets formed inside the cover
How did water reach the top of the bag, when I poured it at the bottom?
The warm water turned into water vapour and rose up. The plastic at the top is cooler, so the vapour cooled and became drops. This is condensation.
The droplets grow bigger, slide down the side and fall back into the water
Why do the drops not stay on top?
Small drops join to make big, heavy drops, and heavy drops slide down. In the sky the same thing happens and we call it rain.
The level of the coloured water does not change much
Where did the water go and come back from?
The bag is sealed. The water only changed its form — liquid to vapour and back to liquid. Nothing left the bag.
The drops on the plastic are clear, not blue
Why did the colour not go up with the water?
Only water evaporates. The colour was left behind, just as sea salt is left behind when sea water evaporates.
The big idea: The bag is a tiny model of the Earth. The coloured water is the sea. The sunny window is the Sun. The mist and drops at the top are the clouds. The drops running down are the rain. Because nothing can get out of the sealed bag, you can see clearly that water is never used up — it only travels and changes form.