Grade 4 (age 9-10)

grade 4 The Water Cycle

A puddle on the playground after rain dries up once the sun comes out, but the water has not vanished: it has turned into water vapour and risen into the sky. Earth's water is neither made new nor used up; it changes form and travels endlessly between the sea, the sky, and the land. When the sun warms the sea, water turns into vapour and rises; up high the vapour cools into tiny droplets that form clouds. Rain and snow falling from the clouds flow along rivers back to the sea. Follow the numbers ① to ④ in the moving picture to see where the water goes.

Water goes round and round

💧 Water's journey

①When the sun warms water in the sea and on land, it turns into vapour and rises into the sky (evaporation)

②High in the sky it is cold, so the vapour turns into tiny droplets that form clouds (condensation)

③When the droplets in a cloud grow big and heavy, they fall as rain or snow (precipitation)

④Water that falls on land flows along rivers or soaks into the ground, and then returns to the sea

⑤The heat of the sun powers this whole journey

The three forms of water

🧊 The three forms of water

①Solid ice: water freezes when it gets colder than 0 °C

②Liquid water: the flowing form we see in rivers and seas

③Gaseous water vapour: it is invisible, and a little evaporates from a water surface even on cold days

④On its trip around the water cycle, water changes between vapour, droplets, and ice

Summary

The water cycle

Sea → evaporation → clouds → rain and snow → river → sea

Water keeps going round, changing its form as it goes

Changes of state

Ice (solid) ↔ water (liquid) ↔ water vapour (gas)

Water changes form depending on the temperature

🎯 Key points

①The water cycle goes evaporation → condensation (clouds) → precipitation (rain and snow) → flowing in rivers → evaporation again

②The heat of the sun drives the water cycle

③As it cycles, water changes between solid, liquid, and gas

④Earth's water is not made new; it goes round and round

⑤Thanks to the water cycle, rain falls and rivers keep flowing

Examples and Unit Test

Example 1

What is it called when seawater is warmed by the sun and rises into the sky as water vapour?

When the sun warms the sea, water turns into vapour and rises into the air.

This change of water into vapour at the water's surface is called evaporation.

▸ Evaporation

Laundry dries because the water in the clothes evaporates too.

Example 2

What is it called when water vapour rising into the sky cools and gathers into tiny droplets to form clouds?

When the vapour rises high into the sky, the surrounding air is cold, so the vapour cools.

The cooled vapour turns into tiny droplets that gather into clouds; this is called condensation.

▸ Condensation

The droplets that form on the outside of a cold glass are water vapour from the air condensing too.

Unit-test style

Which statement about the water cycle is correct?

①Evaporation is water vapour turning into water

②Water changes its form as it cycles

③Earth's water is gradually made new as it cycles

④The water cycle does not need the sun's heat

⑤Clouds are lumps of frozen water

▸ ② Water changes its form as it cycles

Water cycles through evaporation, condensation, and precipitation, changing between vapour, droplets, and other forms.

Evaporation is water turning into vapour (①), Earth's water is not made new but cycles (③), the cycle is driven by the sun's heat (④), and clouds are gatherings of tiny droplets (⑤).

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Last updated 2026-10-17