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 three-fourths, 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.

Water 75%

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 Review

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 EarthThere 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

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.

Lesson Review