Water Cycle IGCSE Biology 0610

The Water Cycle: Evaporation, Condensation and Precipitation

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

Key concept

The water cycle moves water between the atmosphere, land and oceans. Water evaporates from surfaces and transpires from plants, rises and condenses into clouds, then falls as precipitation. It runs off land or percolates through soil back to rivers and oceans.

The water cycle is straightforward but must be described using the correct biological and physical terms. Students often forget transpiration as a biological contribution and fail to explain why condensation occurs at altitude.

Evaporation and transpiration

Evaporation occurs when water at the surface of oceans, lakes and rivers absorbs heat energy and changes from liquid to water vapour. This water vapour rises into the atmosphere.

Transpiration is the biological contribution: water evaporates from the surfaces of mesophyll cells inside leaves and diffuses out through open stomata. In forested areas, transpiration can return a large proportion of rainfall to the atmosphere. Together, evaporation and transpiration are sometimes called evapotranspiration.

Condensation and cloud formation

As water vapour rises, it cools because the temperature decreases with altitude. When the air cools to the dew point, the water vapour condenses onto tiny particles of dust or pollen in the atmosphere, forming tiny water droplets. These droplets collect together to form clouds.

Condensation is the change of state from gas to liquid. It releases heat energy into the surrounding air. Students should not say water "turns into clouds" without mentioning condensation.

Precipitation and return to the surface

When water droplets in clouds grow large enough, they fall as precipitation (rain, snow, sleet or hail). The water reaches the ground and follows several paths:

Surface runoff: Water flows across the land surface into rivers and streams, eventually reaching the sea. Infiltration and percolation: Water soaks into the soil and may percolate deeper into underground aquifers. Absorption by plants: Plant roots absorb water from the soil, which is used in photosynthesis or lost through transpiration, returning it to the atmosphere.

Try a focused question (3 marks)

Describe how water from the ocean can end up inside a plant cell.

Show the answer and marking guidance

Water evaporates from the ocean surface and rises as water vapour.
The vapour cools, condenses into clouds, and falls as precipitation (rain) onto the land.
The rainwater soaks into the soil and is absorbed by plant roots by osmosis.

Original Cambridge-style practice written for this site. It is not an official Cambridge past-paper question.

Common mix-ups to avoid

Check these points against your own answer before moving on.

Forgetting transpiration as part of the water cycle.
Saying water vapour rises because it is "hot" rather than because it is less dense.
Not mentioning condensation when describing cloud formation.
Confusing precipitation with condensation.