Download The Water Cycle

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TEKS Review
4.8B
TEKS 4.8B describe and illustrate the continuous movement of water above and on the surface
of Earth through the water cycle and explain the role of the Sun as a major source of energy in
this process
The Water Cycle
Water on Earth
Phases
We can’t live without water. Water covers
more than three-fourths of Earth’s surface.
Approximately 97% of the water on Earth is salt
water. We cannot use salt water to drink or
water our crops. We would have to take the salt
out of the water, and that is very expensive to
do. The other 3% of Earth’s water is fresh.
However, two-thirds of that water is frozen in
the ice caps and glaciers. It is not available for
our use. This means that only about 1% of all
the water on Earth’s surface is usable for
humans and land animals. This fresh water is
found in lakes, rivers, streams, ponds, in the
ground, and as humidity in the atmosphere.
Evaporation is the process in which liquid
water changes into water vapor. The speed of
evaporation depends on temperature. During the
water cycle, the sun warms some of the water in
the oceans, freshwater lakes, and rivers. The
water on the surface evaporates. Plants absorb
water from the soil and transfer the water
through the stems to the leaves. Once the water
reaches the leaves, some of it evaporates into
the air as water vapor. This process of
evaporation through plant leaves is called
transpiration.
Recycled Water
Earth has what we call a closed system for
water. We do not gain water from anywhere
else, and we do not lose water to anywhere. The
water you drink has been on Earth for billions of
years.
States of Water
Water exists as a solid, a liquid, and a gas at
temperatures common on Earth’s surface. Most
of the water on the surface is liquid water.
Water in the solid form is called ice. Water in
the form of a gas is called water vapor.
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Condensation is the opposite of
evaporation. Water vapor turns back into a
liquid in the atmosphere. We see the tiny drops
of water in the air as clouds or fog. The water
droplets form on tiny particles of dust, salt, and
smoke in the air. As the droplets grow, they
become heavier and start to fall. Precipitation
is water in its liquid or solid form falling from
the atmosphere to Earth’s surface. Rain, snow,
sleet, and hail are some forms of precipitation.
Much of the water that returns to Earth as
precipitation runs off the surface of the land and
is collected in streams, rivers, ponds, and lakes.
Small streams flow into larger streams, then into
rivers, and later into the ocean. Through surface
runoff, much of the water returns to the oceans,
where a great deal of evaporation occurs.
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Some precipitation soaks into the ground.
Water that is underground is called
groundwater. Groundwater trickles slowly
down through the soil until it reaches rock.
There, underground streams may form. Some
groundwater returns to the surface as springs or
in low spots on Earth’s surface.
TEKS Review
4.8B
Movement of Water
The water cycle is a continuous circulation
of water and water vapor between Earth and the
atmosphere. It is an ongoing process that has no
beginning and no ending. The heat and energy
for the cycle come from the sun. Water vapor
rises from oceans, lakes, rivers, forests, fields,
plants, and animals by the process of
evaporation. The evaporated water is carried
into the atmosphere, where it cools and develops
into clouds and fog through condensation. It
falls back to Earth as precipitation, completing
the cycle.
The Water Cycle
Water vapor in the air
condenses, forming
clouds.
Water returns to
Earth’s surface as
precipitation.
Evaporation from the
leaves of plants is
called transpiration.
Some precipitation soaks
into the soil and becomes
groundwater. Some water
stays on the surface in
streams, ponds, lakes, and
rivers.
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Water evaporates from
the ocean and other
bodies of water. The sun
is the source of energy
that causes evaporation
and drives the water
cycle.
Water on Earth’s surface
flows toward the ocean.
Trace the cycle of water in
this diagram with your
finger.
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4.8B
Name ______________________________________ Date _________
Hands-On Activity
Model the Water Cycle
Materials
In this activity, you will make a model of the water cycle. Then you
will use the model to make inferences about what happens during
the water cycle.
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graduated cylinder
water
small plastic cup
zip-top plastic bag
Procedure:
1. Using the graduated cylinder, measure and pour 100 mL of water into the cup.
2. Open a plastic bag, and carefully put the cup inside. Then seal the bag. Be careful not to
spill any water from the cup.
3. Place the sealed bag near a sunny window. Predict what will happen to the water in the
cup.
4. Leave the bag near the window for 3 or 4 days. Observe the cup and the bag each day.
Record what you see.
5. Remove the cup from the bag. Measure the water in the cup only by pouring it back into
the graduated cylinder. Use the numbers you recorded to find any difference between the
amount of water poured into the cup and the amount of water removed from the cup.
Discussion Questions:
1. What did you observe during the time the cup was in the bag?
2. What happened to the water in the cup?
3. Scientists often infer the causes of what they observe. What can you infer about where the
water in the bag came from?
4. If you could accurately measure the volume of water in the bag, what do you predict it
would be? Explain.
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TEKS 4.8B
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TEKS Review
4.8B
The Water Cycle
Label the parts of the water cycle shown in each image below.
What role does the sun play in the water cycle?
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List four types of precipitation.
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Why is the water cycle important for living things on land?
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TEKS 4.8B
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TEKS Assessment 4.8B
Fill in the letter of the best choice.
Which is the process in which liquid
water turns into water vapor?
Where does most of the water that
evaporates on Earth come from?
evaporation
lakes
condensation
ponds
transpiration
oceans
precipitation
creeks
Which is the process in which water
evaporates from plants and goes into the
atmosphere?
Which of the following shows the source
of energy for the water cycle?
evaporation
condensation
transpiration
precipitation
What are clouds made of?
wind
cotton
sunlight
tiny drops of water
Which of the following is the term for
water that falls to the ground?
evaporation
condensation
transpiration
precipitation
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Answer Key
Hands-On Activity (p. 3)
1. The amount of water in the cup dropped. Some drops of water formed on the inside of the
bag.
2. The water in the cup evaporated.
3. The water in the bag must have come from the water that started out in the cup.
4. It would equal the amount of water lost from the cup.
Student Response Activity (p. 4)
1. precipitation; evaporation; condensation
2. The sun is the energy source that drives the water cycle. It causes water to evaporate from
Earth’s surface and to transpire from the leaves of plants.
3. rain, snow, sleet, and hail
4. All living things need water to survive. Precipitation brings fresh water to the land.
Without precipitation, all water on land would eventually drain to the ocean.
TEKS Assessment (p. 5)
1. A
2. C
3. D
4. D
5. C
6. A
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TEKS 4.8B
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