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Chapter Five: Water
Close your eyes and imagine…
Bright sunlight gives way to
rain clouds. Little splashes
of water appear on the lake.
Suddenly rain is pouring
down all around you. Your
face and clothes are quickly
soaked. Too bad you don’t
have the waterproof
feathers of a duck. Getting
wet can be a bother, but
what makes water so
important?
Lesson 1: Why is Water Important?
You could go without sweets or TV if you had to. But you can’t give up
water. You could not live more than a few days without it.
Living Things and Water
 Water makes up about two-thirds of your body. It helps digest food
into small particles. Water in your blood carries materials to every
part of your body. It also carries wastes away from every part.
 Water helps keep your body at the correct temperature. Water in your
body holds onto its heat, keeping you warm. If your body heats up,
you might sweat. The water in sweat carries heat away from your
body.
 Some organisms must spend their entire lives in water. Many of these
creatures are very small. Daphnia are less than 1.5 mm long and live
mostly in ponds and lakes.
The Planet of Water
 You could call Earth “the blue
planet”. That’s because threefourths, or 75%, of Earth’s
surface is covered with water.
 Most of Earth’s water is salty
ocean water.
 Water is found in many different
places. Some moves downward
into the ground. Some is frozen
in ice. A small amount of water is
found in the air as an invisible
gas called water vapor.
Land 25%
Water 75%
Lesson Review
1. How does water help you live?
2. Why is Earth called the “blue planet”?
Scientist’s Journal
Create a mural showing the ways you use water in
your life. Include direct uses of water and ways
others use water to benefit you, such as farmers
growing the food you eat. Write a short sentence
that explains how you use water for each picture.
Lesson Two: How Do Forms of
Water Change?
Imagine if you were to follow a particle of water for year. One day the
particle is rushing down a mountain stream. Later, it is locked in frozen
pond ice. Later still, it is drifting high in the air. On its journey, water
goes through many changes.
Forms of Water
 Cold water can freeze water from a liquid to a solid

Water can also become a gas called water vapor. The process of liquid
becoming a gas is called evaporation. The Sun’s energy evaporates surface
water. Then the water becomes water vapor in the air.
 Water vapor in the air can turn back into a liquid. The process is called
condensation. When air cools, condensation turns invisible water vapor back
into drops of water. Small droplets form clouds and fog.
How Water Moves Around Earth
There is only a certain amount of water on Earth. It must be used again
and again. The movement of water from Earth’s surface into the air and
back again is the water cycle. The water cycle gives us a constant supply
of fresh water.
Water changes form or state as it moves through the water cycle. The
Sun’s energy and winds cause water to evaporate and become water
vapor. Water vapor rises into cooler air, cools, and turns into water
droplets or ice crystals (condensation). When water particles in clouds
grow in size and weight, they fall faster. Water that falls to Earth is
precipitation. Precipitation might be rain, snow, sleet, or hail. The form
of precipitation depends on the temperature at the Earth’s surface.
Some precipitation seeps into the ground. There it becomes
groundwater. Other precipitation falls into streams, rivers, lakes, and
oceans. Water that flows across Earth’s surface is constantly moving
downstream toward the ocean. A lot of ground water reaches the
surface in lower areas where there are streams and rivers. This surface
water evaporates. In this way, the water cycle continues all the time.
The Water Cycle
Lesson Review
1. What are the three forms of water?
2. Name the main steps in the water cycle.
Scientist’s Journal
Write a short story from the perspective of a water droplet
on its journey down a stream, into a river, ending in a large
lake. Use descriptive words and be sure to name the steps
in the water cycle.