2 THE WATER CYCLEWater moves around Earth in a perpetual cycle. In the atmosphere, clouds are made from tiny droplets of water or pieces of ice. Precipitation from the clouds falls on the land and into the lakes, rivers, and oceans. Water then evaporates back into the air. The pattern of condensation, precipitation, and evaporation is called the water cycle. Let’s look at the following diagrams of a water cycle.
3 VOCABULARYWater cycle- The pattern of water moving between the air and the ground over and over again.Evaporation- The sun heats up water that is in lakes, oceans, rivers or on land. The heat energy makes the water rise up into the air as an invisible gas called water vapor.Condensation- When the water vapor rises into the air, it is cooled. The water vapor turn into tiny droplets. These come together to form clouds.Precipitation- When the water droplets in the clouds get too heavy, they fall to Earth as rain. If it is cold enough, these raindrops can become snow, hail or sleet.
8 WATER ON EARTHThe world’s surface is approximately 71% water. Of that percentage, the oceans hold about 97% of Earth’s water.The other 3% of Earth’s water is in the form of lakes, rivers, or glaciers.Some water seeps into the ground. Someday this water might reach the surface again by way of an underground spring. This can actually take thousands of years to happen.
17 WATER ON EARTHRunoff- Water that runs along the surface of the earth instead of seeping in. This water goes directly into a larger body of water.
18 EVAPORATION Evaporation puts water into the air. Solar energy changes water into water vapor.The water vapor rises into the air.Water is constantly evaporating from lakes, rivers, oceans, and even glaciers.Wind helps evaporation happen even faster.The amount of water in the air at any given time can be measured using a psychrometer.A psychrometer measures the amount of humidity in the air. It is measured as a percentage of the air.
21 PRECIPITATION & CONDENSATION Precipitation forms when water vapor cools in the air.The water vapor condenses , or turns back into its liquid form. This process is known as condensation. In this process, very small water drops form and group together into clouds. When the drops get too heavy, rain, snow, or sleet falls out of the cloud as precipitation. The water cycle is said to be balanced because overall, the amount of water that evaporates equals the amount of precipitation that falls.