Water on Earth is always moving. It changes form and travels between the land, oceans, rivers, plants, clouds, and underground. Scientists call this endless movement the water cycle.
1. Water changes state
Water can be a liquid (rain, lakes, oceans), a solid (ice and snow), or a gas (water vapor you cannot see). Heating and cooling make water change from one state to another.
2. Evaporation
When the Sun warms water in oceans, lakes, and puddles, some of that liquid water turns into water vapor and rises into the air. That change from liquid to gas is called evaporation.
3. Transpiration
Plants pull water from the soil through their roots. Some of that water leaves the plant through tiny openings in the leaves and becomes water vapor in the air. That plant water release is called transpiration.
4. Condensation
High in the sky, water vapor cools. As it cools, it turns back into tiny liquid droplets. That change from gas to liquid is called condensation.
5. Cloud formation
Those tiny droplets gather around bits of dust in the air. When enough droplets cluster together, they form clouds you can see.
6. Precipitation
When cloud droplets grow heavy enough, they fall back to Earth as rain, snow, sleet, or hail. Falling water from clouds is called precipitation.
7. Runoff and collection
Rain and melting snow flow across the ground into streams, rivers, lakes, and oceans. Water that gathers in these places is collected until the cycle continues.
8. Infiltration and groundwater
Some water soaks into the soil. It can move down through cracks and spaces in rock and become groundwater stored under the surface.
9. Energy from the Sun
The Sun supplies the energy that warms water and drives evaporation. Without the Sun's heat, the water cycle would slow or stop.
10. Gravity's role
Gravity pulls precipitation down toward Earth and helps water flow downhill in rivers and streams. Gravity keeps water moving through the cycle after it leaves the clouds.