Ch. 13: The Water Cycle Vocabulary: glacier, water cycle, evaporation, water vapor, condensation, precipitation, runoff, groundwater

Earth’s Water Supply Earth is different from most other planets in our solar system in that we have liquid water on the surface of our planet. All life on Earth requires water. Your body, like all other living things, is mostly made out of water. The process through which we get water that we can drink and use is called the water cycle.

Earth’s Water Supply Most of the water on Earth is located in the world oceans. Ocean water is also called salt water, because of the large amount of salt in it. Drinking too much salt water can kill you.

Earth’s Water Supply Most of the freshwater on Earth is frozen in large ice caps near the North and South Poles called glaciers. Some freshwater is found in lakes, rivers, and streams. Most of our drinkable freshwater comes from underground. Water that we find underground is called groundwater.

The Water Cycle The water cycle is the process through which water moves from the oceans to the land and back again. An important thing to know about the water cycle is that it never stops working. Because it is a cycle it has no beginning or end.

The Water Cycle

Parts of the Water Cycle Step 1: Evaporation Evaporation is where the water on the surface of the Earth is heated by the sun and changes into a gas. Water when it turns into a gas is called water vapor. Water vapor is invisible and is always in the air around us. As the water vapor gets hot it rises higher in the sky.

The Water Cycle Step 2: Condensation Condensation is where the water vapor in the air cools back down and changes from a gas back into a liquid. When this happens it reforms into tiny water droplets that are lighter than air. That’s why clouds are able to float high in the sky. They are really made of millions of tiny water droplets all clustered together.

The Water Cycle Step 3: Precipitation Precipitation is where the tiny water droplets that form clouds gather together and become too heavy to stay floating up in the sky. When they get too heavy they fall to the ground. Depending on the temperature, precipitation can be rain, snow, sleet, or hail.

The Water Cycle Step 4: Runoff Some water falls straight back into the ocean or back into rivers or lakes. Some of the water falls on land, and when it does it flows over and under the ground in streams and rivers to areas like lakes, and oceans. This process is called runoff.

Questions About Chapter 13 What are four of the steps in the water cycle? In the water cycle, what happens during evaporation? Describe the condensation process. What are four forms of precipitation? What is a cycle? How is the sun important to the water cycle?