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A Cycle without WheelsBy Trista L. Pollard

What do you call a cycle that is clearand flows? No, it is not an invisiblebicycle floating down the MississippiRiver! It is the earth's water cycle!For millions of years earth hasrecycled or reused its water. Thinkabout it; you could be taking a bath inthe same water used by yourgrandparents when they were kids.Let's look at how the earth reuses itswater.

The earth's water cycle has threemain stages or parts called evaporation, condensation, andprecipitation. These stages repeat over and over again. However, thewater cycle does not happen overnight. In fact, the whole cycle cantake a long time. The reason it's called a cycle is because the watergoes from the earth, through the air, to the clouds, and back to theearth again. This pattern is like a spinning wheel on a bicycle.

Ocean water is an important ingredient in the water cycle. During thefirst stage, evaporation, ocean water is heated by the sun. This causesthe water to evaporate or change into water vapor (gas). The salt fromthe water is left on earth. Don't worry, there are not empty oceanslying around! Since the water cycle is always "spinning," the oceansare always full. After the water changes into gas, it rises into the air.We also see examples of evaporation when the sun dries a puddleafter it rains or when we let the picture we painted dry on the table.

Condensation, the second stage, happens when the water vapor in theair changes back into liquid water or ice. As warm air rises, it meetsthe colder air in the atmosphere. When the warm air and cold air meet,the water vapor is changed into liquid or ice and clouds are formed.Think about the many times you have had ice water or cold soda in aglass. The water drops that are on the outside of the glass are therebecause of condensation. These drops come from the air that is aroundthe outside of the glass.

The last stage is called precipitation. This part of the water cycledelivers the water back to earth. The clouds fill up with water drops orice crystals. When they become heavy, the earth's gravity pulls thewater back to earth. Now you know why we have rain, hail, and snow.Once the rain falls to the earth the water may stay for a long period oftime. Some of the water stays underground among rocks. Eventually,it returns to the surface of the earth where it can be evaporated. This ishow the water cycle starts all over again.

Even though the water cycle is always "spinning," we still need toworry about earth's water supply. Most of the water that falls back toearth ends up in the ocean and becomes salt water. Some of that wateralso becomes ice or glaciers. There is only a small part of the waterproduced by the cycle that can be used at any time. As the earth'spopulation continues to grow, we need to be more careful of how weuse our water. Remember, even though the water cycle is "spinning",it can take a long time for that "wheel" to go around.

A Cycle without Wheels

Questions

1. Water vapor is ______.

A. water that is turned into gasB. water that is turned into liquidC. water on the earth's surfaceD. none of the above

2. The water cycle is always repeating.

A. TrueB. False

3. Most of the water that falls back to earth goes into ______.

A. the riversB. the streamsC. the oceansD. the lakes

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4. Condensation is ______.

A. when water vapor is changed into liquid waterB. when water vapor is changed into iceC. when water vapor does not changeD. when ice is changed into liquid water

5. What is precipitation?

6. When the sun warms the earth, it changes the water on earthinto water vapor that rises into the air.

A. TrueB. False

7. After rain falls to earth, it may ______.

A. stay underground for many yearsB. stay on the earth's surfaceC. absorb into rocksD. none of the above

8. Clouds are formed during the ______.

A. precipitation stageB. evaporation stageC. liquidation stageD. condensation stage

Imagine! You are a raindrop that has just fallen to earth. You havelanded on a friendly oak tree leaf, who is wondering how you landedon him. To make this leaf happy, you need to explain how you arepart of the earth's water cycle. Explain your part in the water cycleusing the voice of the raindrop.

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Cause and Effect: All things are related to each other in some way.What would happen if one of the stages for the water cycle did notexist? Write a news story which talks about the disappearance of oneof the water cycle stages (evaporation, condensation, or precipitation).Make sure you explain what happened to that stage to cause it todisappear, and what will happen to the water cycle now that the stageis gone. Be creative, but detailed.