Download A Cycle without Wheels

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Date
A Cycle without Wheels
By Trista L. Pollard
What do you call a cycle that is clear and flows? No, it is not an
invisible bicycle floating down the Mississippi River! It is the earth's
water cycle! For millions of years earth has recycled or reused its water.
Think about it; you could be taking a bath in the same water used by
your grandparents when they were kids. Let's look at how the earth
reuses its water.
The earth's water cycle has three main stages or parts called
evaporation, condensation, and precipitation. These stages repeat over
and over again. However, the water cycle does not happen overnight. In
fact, the whole cycle can take a long time. The reason it's called a cycle
is because the water goes from the earth, through the air, to the clouds,
and back to the earth again. This pattern is like a spinning wheel on a
bicycle.
Ocean water is an important ingredient in the water cycle. During the
first stage, evaporation, ocean water is heated by the sun. This causes
the water to evaporate or change into water vapor (gas). The salt from the water is left on earth. Don't worry, there
are not empty oceans lying around! Since the water cycle is always "spinning," the oceans are always full. After
the water changes into gas, it rises into the air. We also see examples of evaporation when the sun dries a puddle
after it rains or when we let the picture we painted dry on the table.
Condensation, the second stage, happens when the water vapor in the air changes back into liquid water or ice. As
warm air rises, it meets the 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 a glass. The water drops that are on the outside of the glass are there because of condensation. These drops come
from the air that is around the outside of the glass.
The last stage is called precipitation. This part of the water cycle delivers the water back to earth. The clouds fill
up with water drops or ice crystals. When they become heavy, the earth's gravity pulls the water 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 of time. Some of the water stays underground among rocks. Eventually, it returns to the surface of the earth
where it can be evaporated. This is how the water cycle starts all over again.
Even though the water cycle is always "spinning," we still need to worry about earth's water supply. Most of the
water that falls back to earth ends up in the ocean and becomes salt water. Some of that water also becomes ice or
glaciers. There is only a small part of the water produced by the cycle that can be used at any time. As the earth's
population continues to grow, we need to be more careful of how we use our water. Remember, even though the
water cycle is "spinning", it can take a long time for that "wheel" to go around.
Name
Date
A Cycle without Wheels
Questions
1. Water vapor is ______.
A. water that is turned into gas
B. water that is turned into liquid
C. water on the earth's surface
D. none of the above
2. The water cycle is always repeating.
A. False
B. True
3. Most of the water that falls back to earth goes into ______.
A. the rivers
B. the lakes
C. the streams
D. the oceans
4. Condensation is ______.
A. when water vapor is changed into ice
B. when water vapor does not change
C. when ice is changed into liquid water
D. when water vapor is changed into liquid water
5. What is precipitation?
6. When the sun warms the earth, it changes the water on earth into water vapor that rises into the air.
A. True
B. False
7. After rain falls to earth, it may ______.
A. stay underground for many years
B. stay on the earth's surface
C. absorb into rocks
D. none of the above
8. Clouds are formed during the ______.
A. condensation stage
B. evaporation stage
C. liquidation stage
D. precipitation stage
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Imagine! You are a raindrop that has just fallen to earth. You have landed on a friendly oak tree leaf, who is
wondering how you landed on him. To make this leaf happy, you need to explain how you are part of the earth's
water cycle. Explain your part in the water cycle using the voice of the raindrop.
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 not exist? Write a news story which talks about the disappearance of one of the water cycle
stages (evaporation, condensation, or precipitation). Make sure you explain what happened to that stage to
cause it to disappear, and what will happen to the water cycle now that the stage is gone. Be creative, but
detailed.