The Water Cycle FK – 5.2 (700-800L)_02

Did you ever think about the water you drink, maybe where it came from or how old is it? Maybe you just opened a new bottle of water or you just filled your glass from the faucet. In both cases, you are drinking water that is older than you can possibly imagine. It’s true! Each drop of water in your glass or bottle could be billions of years old. How is that even possible? Simple! Water is recycled through a process called the water cycle.

The majority of Earth’s surface is covered by water. It is found from the equator to the poles. It can also be in many forms, from ice to a gas. You have learned that water can change its form, or state, based on its temperature. In colder regions, water can exist as ice in glaciers on land or as frozen sea water. Both the north and south poles of Earth are covered by ice. In warm regions, water can be found as a liquid in lakes, streams, and oceans. Even the air contains water in the form of a gas. Water in a gaseous state is called water vapor. You may be wondering what does this have to do with water being really old? It is the Sun that powers the recycling process of the water cycle.

Energy from the Sun causes water to evaporate. Most evaporation is from the oceans because they cover so much area. The water vapor rises into the atmosphere. Wind currents carry the water vapor to other locations. Another way liquid water is changed into a gas is transpiration. Transpiration occurs in plants. The plants release water vapor through their leaves. This water vapor also rises into the atmosphere. Once in the air as a gas, water needs a way to turn back into a liquid. Can you think of a way this could happen?

Condensation is the opposite of evaporation and changes water vapor back to liquid water. As air rises higher into the atmosphere, it cools as it expands. Cool air holds less water vapor than warm air, so some of the water vapor condenses into water droplets. Those water droplets may form the clouds you see in the sky. In the clouds, water droplets join with other droplets, becoming bigger and bigger. Water droplets in clouds fall to the earth when they become too heavy for the wind currents to hold them aloft. The water falls as rain if the air is warm. If the air is cold, the water may freeze and fall as snow, sleet, or hail. When water falls from clouds, it is called precipitation. Most precipitation falls into the oceans. Some falls on land.