- Science
- Classes 3-5
- 4 min read
The water cycle
See how water goes round and round: evaporation, condensation, rain and back to rivers and the sea, all powered by the Sun.
Let us begin
The big idea
The water in a puddle today may have been in a cloud last week, and in the sea before that. Water keeps moving around the Earth in a never-ending journey called the water cycle.
The Sun heats water in seas, rivers, lakes and puddles. Some of the water turns into an invisible gas called water vapour and rises into the air. This is called evaporation. Plants also give out water vapour through their leaves. This is called transpiration.
High up, the air is cold. The water vapour cools and turns into tiny drops of water. These tiny drops gather together to make clouds. This is called condensation.
When the drops in a cloud become big and heavy, they fall to the ground as rain. In very cold places they fall as snow or hail. Rain, snow and hail are together called precipitation.
The water collects in rivers, lakes and the sea, or soaks into the ground. Rivers carry water down to the sea. Then the Sun heats it again, and the cycle begins once more.
The water cycle gives us fresh water. It is why monsoon rains fill our rivers and fields.
Worked examples
See how it works
Wet clothes drying
Wet clothes on a line dry because the water in them evaporates into the air. The Sun and the wind make it faster.
Water drops on a cold glass
Water vapour in the air touches the cold glass, cools and turns back into tiny drops. This is condensation, the same thing that makes clouds.
Order of the cycle
Sun heats sea water, evaporation, water vapour rises, condensation forms clouds, precipitation brings rain, rivers carry water back to the sea.
Try it at home
Vanishing puddle and cold-glass drops
You will need
- A spoon or small cup of water
- A dry flat stone or tile in the sun
- A glass
- Cold water and a few ice cubes
- Chalk or a pencil
What to do
- Pour a small puddle of water on a dry stone or tile in a sunny place. Draw a line around the puddle with chalk.
- Come back every 10 minutes and look at the puddle. Draw a new line each time.
- Where has the water gone? It has evaporated into the air.
- Fill a glass with cold water and ice cubes. Leave it on a table for 15 minutes.
- Look at the outside of the glass. Water drops have appeared because water vapour from the air condensed on the cold glass.
Ask a grown-up: Use only cold tap water and ice. Do not use hot water.
Fun fact
The water you drink today has been going round the water cycle for a very, very long time.
Practice sheet
Check what you learned
Practice sheet: The water cycle (Classes 3-5, Science)
- What gives the heat that starts the water cycle?
- What is the change of liquid water into water vapour called?
- What is the change of water vapour into tiny drops of water called?
- Name the process by which clouds give rain, snow or hail.
- What are clouds made of?
- Where does most of the rain water finally go?
- Why do wet clothes dry faster on a sunny, windy day?
- Why do drops form on the outside of a glass of cold water?
- Put these in order: rain falls, water evaporates, clouds form, rivers flow to the sea.
- Plants also add water to the air. What is this called?
Answer key
Answers: The water cycle
- The Sun.
- Evaporation.
- Condensation.
- Precipitation.
- Tiny drops of water (and in cold clouds, tiny ice crystals).
- Into rivers, lakes and the sea, or it soaks into the ground.
- The Sun and the wind make the water evaporate faster.
- Water vapour in the air touches the cold glass and condenses into drops.
- Water evaporates, clouds form, rain falls, rivers flow to the sea.
- Transpiration.