Water on Earth is always changing state and place. This is knows as the water cycle.

This animation shows one molecule of water completing the hydrologic cycle. Credit: NASA/Goddard Space Flight Center.


When the Sun heats water, water vapour rises. This is evaporation.


When the water vapour cools, it turns into water drops and forms clouds. This is condensation.


The wind moves the clouds. When the clouds cool, water from the clouds falls as rain. If it is very cool, the water freezes and falls as snow. Rain and snow are both types of precipitation.


Precipitation eventually goes to the river and back to the sea. This is called collection. Now the cycle begins again.

The Water Cycle | The Dr. Binocs Show
Ever wondered how it rains?


Thirstin’s Water Cycle is a flash animation about four aspects of  the water cycle: rain, water storage, vapor and clouds.


A water-cycle diagram by USGS and FAO.