What is the water cycle?

Key Terms Water cycle Evaporation Condensation Precipitation Transpiration Infiltration Runoff

The Water Cycle Water is always changing state. As water evaporates from the surface, it changes from a liquid to a gas. In the atmosphere, the water vapor condenses to a liquid and forms clouds. Finally, the water falls back to Earth as precipitation. This repeated movement of water between the earth and the atmosphere is called the water cycle.

The Water Cycle Illustrated

Evaporation Evaporation is the process when liquids change to gases. Most of Earth’s surface is covered with water. When liquid water absorbs enough heat energy from the Sun, it changes into water vapor.

Condensation The changing of a gas to a liquid is called condensation. When air containing water vapor is cooled, the water vapor loses heat and changes to a liquid. Water vapor condenses into tiny droplets of water. These droplets join together to form clouds. If the temperature is freezing, ice forms. A cloud is a collection of water droplets or ice crystals.

Condensation

Precipitation Water that falls to Earth from the atmosphere is called precipitation. Rain and snow are the two main forms of precipitation. As the water droplets in the clouds grow bigger, they become too heavy to stay in the air and gravity pulls them toward the Earth.

Precipitation

Transpiration Transpiration is the process of water loss from plants

Soaking it Up = Infiltration Infiltration happens when water soaks into the soil from the ground level. It moves underground and moves between the soil and rocks.

Runoff Runoff is the movement of land water to the oceans, chiefly in the form of rivers, lakes, and streams. Runoff consists of precipitation that neither evaporates nor penetrates the surface to become groundwater.

Checking Concepts The process by which a gas changes to a liquid is called __________. The main forms of precipitation are __________, and _________. The ______________ is the repeated movement of water between Earth and the atmosphere.

Answers Condensation Rain and snow Water cycle

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