Rain falls from the sky. Where does it come from? Water goes on a trip. It goes round Earth.

Most of Earth's water is in the ocean. Water is in the air too. It is on the land. It is under the ground.

The sun is hot. Its heat makes water leave the ocean. It leaves lakes and streams too. We say the water evaporates. It turns to vapor. Vapor is a gas in the air.

Plants and trees send vapor up too. We call this transpiration.

The air gets cool as it goes up. Cool vapor turns back to water. We call this condensation.

The vapor goes up high. It cools and turns to drops. The drops form clouds. Clouds are made of water drops.

Rain and snow fall from clouds. Water that falls from clouds is called precipitation.

Some rain soaks into the soil. It becomes groundwater. Runoff from the land fills rivers and lakes.

When snow and ice melt, the water flows to the ocean. Rivers and streams take water to the ocean too. Then the sun lifts it up again.

Words to know

• evaporates: turns to gas
• condensation: gas turning liquid
• precipitation: falling rain, snow
• groundwater: water underground