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The Water Cycle Facts About Water • Water is the most important material on earth. • Water continuously changes forms so it can be used and recycled. • Matter on earth, including water, is never created or destroyed. • Approximately 70% of the planet is covered in water. Forms of Water • Water can be found in three forms – Liquid • Example: oceans, lakes, rivers, streams, groundwater – Gas • Example: water vapor – Solid • Example: ice, snow The Water Cycle •Precipitation •Runoff •Evaporation •Condensation Precipitation • Precipitation occurs when droplets in clouds join together and become large enough. • Precipitation can fall in the form of rain, snow, sleet, or hail, depending on the temperature of the air through which the droplets fall. Runoff • After precipitation occurs water moves through the environment back towards larger bodies of water. http://www.desktopscenes.com/Scenes%20from%20Glacier%20National%20Park%20(2004)/Runoff%20 Waterfall%20Near%20Logan%20Pass.jpg Evaporation • Evaporation happens at all times. • The rate of evaporation increases when temperatures are higher and air surrounding a water source is drier. • Living things also contribute through perspiration, which is the release of water vapor through the skin. • We can also exhale water vapor in our breath. Condensation • The air can hold only a limited amount of water vapor. • The amount of water vapor the air can hold depends on the temperature of the air. – Warm air can hold more water vapor than cold air. • When air reaches a temperature where it can hold no more water vapor it is said to be saturated. This is called the dew point. • When the temperature falls below the dew point the water vapor begins to condense, or come together. • High above the ground clouds form. Near the ground fog forms. • On solid ground dew or frost forms depending on the temperature. Condensation • When most air cools, water vapor condenses and clings to tiny particles of dust, smoke and salt, forming clouds. • When the droplets in clouds join together and become large enough, they fall to the ground as precipitation. Pictures • All pictures are from Microsoft Clipart.
