AQA Biology 4.7.2.2
The water cycle
The same water has been going round for millions of years. Follow one drop from the sea and back, and find out why the rain on land is fresh when the sea is salty.
Combined Science · Foundation tier
Start here
A puddle on a sunny afternoon.
After a morning shower there is a puddle on the playground. By the end of a warm, sunny afternoon it has gone, and the ground under it is dry.
If you had to guess, did most of the water go down into the ground, or up into the air?
The cycle · one drop
Follow a drop from the sea and back.
Water is not used up. It is continuously evaporated and precipitated, moving between the sea, the air, the land and living things. At each step, pick the process.
Step 1 of 9
The drop is in the sea, which is salty.
What happens next?
- Evaporation
- Energy from the Sun turns liquid water from seas, lakes and soil into water vapour.
- Transpiration
- Plants lose water vapour from their leaves, through the stomata.
- Condensation
- Rising vapour cools and turns into tiny liquid droplets. Clouds are made of these droplets.
- Precipitation
- Droplets join into larger drops and fall as rain, snow, sleet or hail.
- Runoff and groundwater
- Water flows over the land into rivers, or soaks into the ground, and drains back to the sea.
Why it matters · fresh water
The sea is salty. The rain is not.
When sea water evaporates, only the water turns to vapour. The dissolved salts are left behind in the sea. So the vapour, and the rain or snow it becomes, is fresh water.
That fresh water lands on the land, where plants and animals can use it, before it drains back into the sea. This is why the water cycle matters to living things on land.
Plants
Take in water from the soil through their roots, carry it up to the leaves, and lose water vapour by transpiration.
Animals
Take in water by drinking and in food. Return it in urine and faeces, in sweat, and as water vapour in the air they breathe out.
Think again · clouds
“Clouds are made of water vapour, like steam.”
Your call
ChooseWhat is a cloud made of?
Sort
Which way is the water going?
Place each process by what it does to the water.
Tap a card, then tap the box it belongs in. Tap a placed card to take it back.
Command words in this lesson
- Describe
- Name each process in order: where the water goes, and in what form.
- Explain
- Give the reason: salts are left behind, so the rain is fresh water.
- Interpret
- Name the process each arrow on a cycle diagram shows.
Key fact
The water cycle provides fresh water for plants and animals on land before it drains into the seas. Water is continuously evaporated and precipitated.
Key note · AQA 4.7.2.2
The water cycle
- Water is continuously evaporated and precipitated: it is recycled, not used up.
- Evaporation: liquid water from seas, lakes and soil becomes water vapour, using energy from the Sun.
- Transpiration: plants lose water vapour from their leaves through stomata.
- Condensation: rising vapour cools into tiny droplets, forming clouds. Precipitation: rain, snow, sleet or hail.
- Runoff and groundwater carry water back to the sea.
- Salts stay behind when sea water evaporates, so precipitation is fresh water for plants and animals on land.
Photograph this card. Tomorrow, cover it and say each line first.
Previous and next
Connects to
Ask MrBadmus
Not sure which arrow is which?
The cycle diagram is schematic and not to scale.