Water cycle notes - Year 7 Geography
The water cycle is the continuous movement of water between the sea, the air and the land.
The Sun's heat powers the whole cycle.
Evaporation: heat turns liquid water into water vapour, a gas. Most evaporation happens over the oceans.
Transpiration: plants release water vapour from their leaves.
Condensation: as vapour rises it cools and turns back into tiny liquid droplets, which form clouds.
Precipitation: when droplets in clouds grow heavy they fall as rain, snow, sleet or hail.
Collection: water gathers in oceans, lakes, rivers and underground.
Runoff: water that flows over the land surface into rivers and streams.
Infiltration: water soaking down into the soil.
Groundwater: water stored in soil and rock underground. The top of it is called the water table.
An aquifer is a layer of rock that holds groundwater.
About 97% of Earth's water is salt water in the oceans.
Only about 3% is fresh water, and most of that is frozen in ice caps and glaciers.
Sublimation: ice turning straight into vapour without becoming liquid first.
Class experiment: we covered a bowl of warm water with cling film and put ice on top.
Droplets formed on the underside of the film. This showed condensation.
Mr Okafor said a cloud is made of tiny droplets, not of vapour.
Key terms to learn: evaporation, condensation, precipitation, collection.
The water cycle has no start or end point.
Rivers flow downhill towards the sea because of gravity.
Deserts get little precipitation, less than 250 mm per year.
Rainforests get lots of precipitation and have high transpiration.
Homework: draw and label the cycle with arrows.
Test on Friday.
