The water cycle · Grade 7
The water on Earth is used again and again. The Sun heats water so that it evaporates; the vapour rises, cools and condenses into clouds; water falls as rain or snow; and it collects in rivers, lakes and seas, ready to evaporate again. This is the water cycle.
Key facts
- Evaporation: the Sun heats water in seas, lakes and rivers, and it turns into water vapour (a gas).
- Condensation: water vapour rises, cools and turns into tiny droplets that make clouds.
- Precipitation: the droplets join, get heavy and fall as rain, snow, sleet or hail.
- Collection: water runs off the land into rivers, lakes and seas, or soaks into the ground (infiltration).
- Plants also give off water vapour from their leaves (transpiration).
- The Sun provides the energy. When salty sea water evaporates, the salt is left behind, so rain is fresh water.
- Evaporation is faster when it is warm, when it is windy and when the surface area is large.