The earth has a limited amount of water. That water keeps going around and around and around in what we call the “ Water cycle”. It is the only way that Earth can be continually supplied with fresh water. The sun is the most important part of renewing our water supply. It can be solid (ice), a liquid (water), or gas (water vapor). Water on earth is always changing. How do these changes happen? It is made up of a few main parts: evaporation (and transpiration), condensation and precipitation. Evaporation is when the sun heats up water in rivers or lakes or the ocean and turns it into the vapor. The water vapor leaves the river, lake or ocean and goes into the air. Condensation is water vapor in the air gets cold and changes back into liquid, forming clouds. If heat is taken away from liquid water, it freezes to become ice. Water vapor condenses into millions of small or tiny droplets that forms a cloud.
Clouds lose their water as rain or snow, which is called percipitation. Percipitation occurs when so much water has condensed that the air can’t hold it anymore. The clouds get heavy and heavy and water falls back to the earth in the form of rain, hail, snow. It is either absorbed into the ground or runs off into rivers. Water that was absorbed into the ground is taken up by plants. Plants lose water from their surface as vapor back into the atmosphere. Water that runs off into rivers flows into the atmosphere. Water that runs off into rivers flows into ponds, lakes, or oceans where it evaporates back into the atmosphere. The cycle continues.