The Water Cycle

The water cycle describes how water moves between the land, the oceans and the atmosphere. The Sun provides the energy that keeps the cycle going.

1. Evaporation

Heat from the Sun warms water in oceans, lakes and rivers. Some of it turns into water vapour, an invisible gas that rises into the air. Plants also release water vapour through their leaves; this is called transpiration.

2. Condensation

As water vapour rises, it cools down. Cool air cannot hold as much vapour, so the vapour condenses into tiny droplets that gather around dust particles and form clouds.

3. Precipitation

When the droplets in a cloud join together and become heavy, they fall back to Earth as rain, snow, sleet or hail.

4. Collection

Water collects in oceans, lakes and rivers, or soaks into the ground as groundwater. From there it evaporates again and the cycle repeats.

Key words

• Evaporation – liquid water changing into water vapour
• Condensation – water vapour cooling into liquid droplets
• Precipitation – water falling from clouds
• Runoff – water flowing over land into rivers and seas

Homework: draw and label a diagram of the water cycle with all four stages.