Chapter 1

Earth: The Water Planet

Section 3

The Water Cycle

The Water Cycle

• The water cycle continually moves water through the living and non-living parts of the environment.

• The sun’s energy is what drives this cycle.

Water Evaporates

• As the sun warms the surface of a body of water, some of the water molecules change from a liquid to a gas and rises into the atmosphere in a process called evaporation.

Water Evaporates

• Water vapor can also be released into the atmosphere from plants that give off water through their leaves in a process called transpiration.

Clouds Form

• The higher in the atmosphere these gas molecules go, the colder it gets, causing them to turn back into liquid water in a process called condensation.

• Condensed water droplets in the sky tend to clump together around tiny dust particles, forming clouds.

Water Falls as Precipitation

• As more water condenses, the cloud’s water droplets get larger and larger until eventually they fall back down towards Earth in a process called precipitation.

Water Falls as Precipitation

• Once the water falls onto Earth, it can take a number of paths before it eventually goes through the cycle again

A Global Process

• Precipitation and evaporation are balanced around the world.

• We may feel like we are getting a lot of rain, but somewhere in the Sahara Desert, they are barely getting any rain.