The Sun lifts water, and cooling brings it back

Years 3–8Stage 2 to Stage 4Run it

The Sun's energy lifts water from the sea, soil and plants as invisible vapour. Rising air cools, clouds form and rain falls. The same water goes round and round.

A cross-section from the sea to a hill covered in trees and grass. Arrows from the Sun bring energy to the sea, and water vapour rises from it. Evaporation from the sea: Moderate. Water vapour also rises from the trees. The vapour is carried over the land and rises to a cloud over the hill, and rain falls from the cloud onto the hill. On the ground, some rain runs off over the surface to the sea, and some soaks in and seeps through the ground as groundwater to the sea. Rain that runs off: A little. Rain that soaks in: A lot. A ringed dot marks one water particle. State of the particle: Liquid water. — The Sun's energy lifts water from the sea, soil and plants into the air. Follow one ringed water particle round the cycle.
Evaporation
Transpiration
Condensation
Precipitation
Runoff
Soaking in
Groundwater
Key Amber arrows from the Sun: the energy it sends to the sea. Dashed grey arrows: water vapour, an invisible gas, moving. Solid blue: liquid water moving, falling as rain or flowing along an arrow. A wider arrow carries more of the rain. Pale blue under the ground: groundwater, filling the spaces in soil and rock. Its dotted top edge is where the ground is full of water. A ringed dot: the water particle to follow. In the circles, each blue dot is a water particle: touching in a liquid, far apart in water vapour.

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Where does rain come from, and where does it go?

The Sun lifts water, and cooling brings it back

The Sun's energy lifts water from the sea, soil and plants as invisible vapour. Rising air cools, clouds form and rain falls. The same water goes round and round.

The Sun's energy lifts water from the sea, soil and plants into the air. Follow one ringed water particle round the cycle.

Key Amber arrows from the Sun: the energy it sends to the sea. Dashed grey arrows: water vapour, an invisible gas, moving. Solid blue: liquid water moving, falling as rain or flowing along an arrow. A wider arrow carries more of the rain. Pale blue under the ground: groundwater, filling the spaces in soil and rock. Its dotted top edge is where the ground is full of water. A ringed dot: the water particle to follow. In the circles, each blue dot is a water particle: touching in a liquid, far apart in water vapour.

What do you think?

What is a cloud made of?
- Water vapour, a gas you cannot see
- Tiny drops of liquid water
- Cold air that has turned white
Say why (optional)
Turn the energy from the Sun right down. What happens to evaporation from the sea?
- It stops, because the sea is far from boiling
- It slows down, but some water still evaporates
- It speeds up
Say why (optional)
Rain falls on roofs and roads instead of trees and grass. Where does more of the rain go?
- Into the ground: more of it soaks in
- Over the ground: more of it runs off to the sea
- Nowhere: it stays where it lands
Say why (optional)

Your explanation

Explain how energy from the Sun, and cooling in the air, keep the same water moving round the cycle.

The idea, step by step

Not to scale

2 · EvaporationSunlight warms the sea. Water particles escape from its surface into the air as water vapour, though the sea is far below 100 °C.
3 · Weaker sunshineWith less energy from the Sun, fewer particles escape each second. Evaporation slows down, but it does not stop.
4 · CondensationAir cools as it rises. Water vapour condenses into tiny drops of liquid water: a cloud. Water forms on a cold can the same way.
5 · PrecipitationRain falls from the cloud onto the hill. Snow and hail are precipitation too.1 Evaporation · 2 Transpiration · 3 Condensation · 4 Precipitation · 5 Runoff · 6 Soaking in · 7 Groundwater
6 · Rain on a townRoofs and roads stop rain soaking in, so much more of it runs off over the ground, through drains and rivers to the sea.1 Evaporation · 2 Condensation · 3 Precipitation · 4 Runoff · 5 Soaking in · 6 Groundwater
7 · Back to the seaUnder trees and grass, more rain soaks in and seeps slowly through the ground to the sea. The same water can go round again.1 Evaporation · 2 Transpiration · 3 Condensation · 4 Precipitation · 5 Runoff · 6 Soaking in · 7 Groundwater

The water cycle, stage by stage, and what drives each one

Process	What happens to the water	What drives it	In the first figure
Evaporation	Liquid water turns into water vapour, a gas	Energy from the Sun
Transpiration	Plants give off water vapour	Energy from the Sun
Carried by the air	Water vapour is carried along and up by moving air	Moving air
Condensation	Water vapour turns back into liquid water	Cooling as the air rises
Precipitation	Water falls from the cloud	Gravity
Runoff	Water flows over the ground to the sea	Gravity
Soaking in (infiltration)	Water soaks into the ground	Gravity
Groundwater flow	Water seeps slowly through the ground to the sea	Gravity
Collection in the sea	Water gathers in the sea, and evaporates again	Gravity	Shown

Try it in the Lab

Practicals with real materials, each with its safety card.

Water cycle in a bag on a sunny windowYear 4Bench practicalLow risk
Where does the water on a cold can come from? Finding the dew pointYear 4Bench practicalLow risk
Evaporation race: sun, shade, wind and surface areaYear 4Bench practicalLow risk
Catchment model: where the rain goesYears 5–6Fieldwork and mappingLow risk
Where is Earth's water: dividing one litre by the real proportionsYears 3–4Fieldwork and mappingLow risk
Water cycle in a box: energy that lifts water and cold that returns itYear 10Bench practicalLow risk
Where the Earth’s water is: a 1000 mL model of oceans, ice, groundwater and riversYear 11Bench practicalLow risk

With a learner

Three questions to ask

Where does the water on the outside of a cold drink can come from?
Why does a puddle dry up on a cool day, when it is nowhere near boiling?
Where does rain go after it lands on a road, and after it lands on a grassy hill?

What to expect

Many learners mix up clouds with water vapour, or think the water on a cold can leaked through the metal. Let them predict first, then step to the particles and look inside the cloud.

What to try next

Try the cold can or the water cycle in a bag in Try it in the Lab, above, safety card first.

About this model

What is simplified

Not to scale: the Sun, the cloud, the hill and the particles are drawn far closer together, and far larger, than they are.
The whole cycle goes on all the time, so every process is drawn at once. The ringed particle shows one path round it; other particles take other paths.
The run is not in real time, and a real trip round the cycle takes far longer than the run; how long depends on the path the water takes.
Here the energy from the Sun changes only how fast water evaporates from the sea. The model does not work out how much cloud or rain forms.
The particle takes the path more of the rain takes on that ground: soaking in under trees and grass, running off roofs and roads. Real amounts depend on the soil, the slope and how hard it rains, so the arrows compare; they do not measure.
Plants take up water from the soil and give off water vapour. The town is drawn with no plants, so it gives off none; a real town has gardens and street trees.
In the circles each water particle is a dot, and a cloud drop is drawn as a few touching particles; a real drop holds far more than can be drawn. Air is not drawn.
Clouds high up, where the air is below freezing, also hold tiny bits of ice. Cloud drops form on specks of dust, salt and smoke, which are not drawn.
Rain also falls straight onto the sea; the figure does not show that, to stay clear.

Numbers and their sources

100 °C The boiling point of water at sea-level air pressure, to the nearest degree. The source gives it in kelvin, as the average of several measurements; converted to degrees Celsius it rounds to this value. The same value as the distillation demonstration: one value for a constant across every demonstration. Source: NIST Chemistry WebBook, SRD 69: Water, phase change data (Tboil), read 26 September 2026.

Review

Demonstration: a simplified model. Checked against its written sources, 26 September 2026. Not reviewed by a qualified teacher.

Curriculum references

ST2-SCI-01ST2-6MW-SSC4-CHG-01GE4-2GE4-PRI-01AC9S4U02AC9S3U04AC9S5U04AC9S7U05AC9HG7K01

Reference, not a verified alignment.

All demonstrations Practicals in the Lab