Download A Cycle without Wheels By Trista L

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.
1
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.
2
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.
3
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.
4
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.
5
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.
6
Copyright © 2004 edHelper
Name
_____________________________
Date
___________________
A Cycle without Wheels
1. Water vapor is ____________.
Water that is turned into gas
Water that is turned into liquid.
Water on the earth's surface
None of the above
2. The water cycle is always repeating.
False
True
3. Most of the water that falls back to earth
goes into _________.
The rivers
The lakes
The streams
The oceans
4. Condensation is _______________.
When water vapor is changed into
liquid water
When water vapor does not change
When ice is changed into liquid water
When water vapor is changed into ice
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.
False
True
7. After rain falls to earth, it may
___________.
Stay underground for many years
Stay on the earth's surface
Absorb into rocks
None of the above
8. Clouds are formed during the
___________.
Condensation stage
Precipitation stage
Liquidation stage
Evaporation stage