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Water Cycle

The  earth has a great deal of water, with most of it in the oceans. More than seventy percent of the earth's surface is covered by these oceans. Most of the earth's water (about 97%) is found in the oceans. The rest of our water (the other 3%) is found frozen in the glaciers, as a liquid in our lakes, streams and our drinking water and as a gas in our atmosphere.

Air is made of molecules or pieces with spaces between the pieces. As air moves over water it picks up pieces of water that fit into the spaces between molecules in the air. This water goes for a ride and causes the air to gain moisture. We call this Evaporation. Plants also add moisture to the air through a process call transpiration, where water moves out of a plant and into the air through their leaves.  This moist or Humid air moves around. Warm air carrying more water vapor gets cooled off if it rises up into the atmosphere. As the air cools, the molecules or pieces it is made of come closer together, squeezing out the water. The water condenses as droplets. These droplets form into clouds. When the droplets get large enough that their mass can be pulled towards earth by gravity we get rain. This moisture can also freeze and come down as snow or hail.

This falling water eventually moves flows into streams and towards other bodies of water where it again can be acted on by moving air starting the cycle all over again.


In this Investigation [7]...

Students will discover that every drop of water the Earth has ever known is still here. Water moves into the atmosphere, gets frozen in glaciers, falls from clouds and goes into the ocean. Through experimentation and the playing of a Water Cycle game, students will see how water just moves from place to place.

Investigation Worksheets (PDF's)

Investigation Video's