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  1. 1. The Water Cycle4.4
  2. 2. “Water Cycle” BrainPop Video
  3. 3. What is the Water Cycle?Water covers more that 70% of Earth’s surface and most of it is salt waterSome of Earth’s water is fresh water that is frozen as glaciers and ice capsGroundwater is fresh water that is below the surface ◦ It collects as rain seeps into soil, filling spaces between soil and rockOur supply of water never runs out because of the water cycle ◦ Water cycle: the constant movement of water from Earth’s surface to the atmosphere and back again
  4. 4. Evaporation Evaporation: the change from the liquid to gaseous state When water is heated, particles of the liquid move from the surface of the water to the air above ◦ These particles are always crashing into each other and gain more energy ◦ The warmer water is, the faster it evaporates Earth’s ocean is the largest source of water for evaporation
  5. 5. Condensation Dew on blades of grass is an example of condensation When water vapor in the air cools, it condenses ◦ Remember that condensation is the change from a gas to a liquid In the lower atmosphere, air gets cooler the higher it goes and as it rises it condenses into clouds Clouds often form when air pressure lowers and warm air rises ◦ Warm humid air near the ground rises and condenses once it reaches the cool air above The water vapor condenses when it reaches the surface of those tiny bits of dust in the air
  6. 6. Precipitation Rain, snow, sleet, freezing rain, and hail are all types of precipitation that falls from the clouds ◦ The type of precipitation depends on the temperature of the air between the clouds and the ground Rain ◦ Often starts in the clouds as snow ◦ If the snow falls through air that is above freezing (hotter temperature) on its way to the ground, it melts Snow ◦ Snow starts on the clouds as snow ◦ If the snow falls through air that is below freezing (a colder temperature) on its way to the ground, it remains snow
  7. 7.  Sleet ◦ Starts as snow ◦ The snow melts into rain as it falls through warmer air below the clouds ◦ If there is a layer of freezing air between the warm air and the ground, the rain freezes again Freezing Rain ◦ Forms almost the same way as sleet ◦ The only difference is the layer of freezing air near the ground is thinner ◦ When the rain falls through the thin layer of freezing air, there isn’t enough time for it to refreeze  It becomes supercooled water (a liquid even though its temperature is below freezing)
  8. 8. Hailstones ◦ Round lumps of ice ◦ Start out as small pieces of ice in storm clouds ◦ Winds in the clouds bump these ice pieces up and down and the cloud droplets freeze onto the pieces of ice ◦ These pieces become bigger and bigger and eventually fall from the clouds
  9. 9. Bill Nye’s “Water Cycle” Rap