The idea
Water moves continuously between oceans, atmosphere, land, and living things, driven almost entirely by energy from the Sun.
| Process | What happens | Energy |
|---|---|---|
| Evaporation | Liquid → gas from open water | Absorbed |
| Transpiration | Water vapour leaves plant leaves | Absorbed |
| Condensation | Gas → liquid, forming cloud droplets | Released |
| Precipitation | Droplets grow heavy and fall | — |
| Infiltration | Water soaks into the ground | — |
| Runoff | Water flows over the surface into rivers | — |
Watch where the energy goes
Evaporation absorbs energy — which is why sweating cools you. Condensation releases it, which is why hurricanes are so powerful: they run on the heat released as enormous volumes of vapour condense.
Why pavement matters
Cover ground with asphalt and you replace infiltration with runoff. The water arrives at the creek in minutes instead of days, all at once, carrying road salt and oil with it. That is the mechanism behind most urban flooding.
Curriculum connection
B2.1
investigate interactions between the biosphere, hydrosphere, lithosphere, and atmosphere, and explain why these interactions are important for ecosystem sustainability
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B2.2
explain how naturally occurring phenomena, including the cycling of matter and the flow of energy, contribute to the dynamic equilibrium within and between ecosystems
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