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Chemistry > The Water Cycle

The Earth has a limited supply of water. This water is constantly moving around from seas to clouds to rain, being recycled. This process is called 'The Water Cycle'.

The diagram below shows how this water moves around our planet (see fig 1):

Fig 1: The Water Cycle
Fig 1:
The Water Cycle

A simplified explanation is as follows:

As the sun warms lakes and oceans, water that forms them evaporates and rises in the atmosphere.

As the water vapour rises, it cools and turns back into tiny droplets of water, forming clouds.

The water in the clouds falls as rain or snow which then runs back into the seas and lakes where the cycle starts again.

Transpiration occurs where plants lose water into the air.

Some of the water that falls on land as precipitation 'runs off' straight back into rivers and lakes whereas some water seeps into gaps in the Earth's layers. This trapped water is called 'ground water'.

Equipment is available through lab suppliers which recreates the water cycle. Usually water is held in a reservoir and warmed with a lamp. The water that evaporates, clings to the roof section as condensation which them drips back into the reservoir.

The water cycle may be referred to as the 'Hydrological Cycle' especially on American websites. Both describe the same process.