Science
The water cycle: how water becomes a cloud
Water moves between Earth’s surface and the atmosphere. In this example, liquid water evaporates, water vapor condenses into cloud droplets, and water returns as rain.
Three changes to follow
- Evaporation: liquid water becomes invisible water vapor. It can happen below boiling temperature, such as when a puddle dries.
- Condensation: water vapor cools and changes into tiny liquid droplets. Clouds contain droplets, ice crystals, or both; they are not just invisible vapor.
- Precipitation: water falls from clouds as rain, snow or other forms. Here it falls as rain.
Liquid water → Water vapor → Cloud droplets → Rain
Where does the water go next?
Rain can flow over land into rivers and lakes, soak into soil, or collect elsewhere. Water can also leave plants as vapor. The complete water cycle has more routes and stores than the lake-to-cloud loop shown here.
A common mix-up
Evaporation and condensation are opposite changes. Evaporation turns liquid into gas; condensation turns gas into liquid. A cloud is visible because of its droplets or ice crystals, while water vapor itself is invisible.
Have a go
Try explaining your answer before opening the hint.
A puddle becomes smaller on a dry day. Which change helps explain this?
Evaporation. Some liquid water changes into water vapor and enters the air.
Why are clouds visible if water vapor is invisible?
Clouds contain tiny water droplets, ice crystals, or both. These scatter light so we can see them.
Does every raindrop return straight to the same lake?
No. Water can soak into soil, flow through rivers, remain stored, or follow other routes before evaporating again.
Try explaining it
Draw a lake, a cloud and rain. Label the upward change “evaporation,” the formation of droplets “condensation,” and the falling water “precipitation.” Then add one route that the simple drawing leaves out.
Read more: USGS Water Science School: The water cycle.