The Blue Planet There’s a reason that Earth is nicknamed “The Blue Planet!” Can you guess what it is? If you said water, you got it right! Just over 70 percent of the Earth’s surface is covered with it. However, most of the water on Earth’s surface is salty seawater—which of course, is not good for drinking. Earth Oceans contain most of the world’s water Clouds consist of tiny droplets of liquid water Ice covers the South and North Poles

Drinkable Drops So how much of the Earth’s water is fresh water? Look at the top part of the diagram to see. Now look at the bottom part of the diagram. How much fresh water is frozen in glaciers and ice caps? When you look at the big picture, it’s easy to see that usable fresh water is a valuable resource. Saltwater (97%) Fresh water (3%) Glaciers and ice caps (68.7%) Groundwater (30.1%) Permafrost (0.8%) Surface water and water in the air (0.4%) Total water Fresh water

States of Matter These macaque monkeys know about one of the most interesting characteristics of water. It can be found on Earth as a liquid, solid, and a gas. Can you spot all three states of matter in the picture?

H 2 O! H 2 O! This symbol means that a molecule of water contains two hydrogen atoms and one oxygen atom. Water molecules move differently in different states of matter. Solid: When water freezes, molecules move farther apart and form crystal shapes. This is why water expands, or gets bigger, when it freezes. Liquid: When ice melts, the crystals break down and molecules move closer together. The molecules are held together but they are still moving. Gas: When water is heated, molecules get more energy and move faster. Eventually they may move fast enough to break free and form water vapor in the air.

The Water Cycle There’s only a certain amount of water on Earth. So water is moved around the planet in a never-ending process called the water cycle. If you look at the diagram carefully, you’ll see that water can exist in all three states (liquid, solid, and gas) as it moves between the oceans, the atmosphere, and the land. Water vapor condenses into clouds as it cools Water vapor rises from the ocean Wind carries clouds inland Water vapor rises from lakes Water falls as rain Water freezes and falls as snow Ice forms glaciers Water seeps into ground Groundwater returns to the ocean Water flows into ocean from rivers and streams Rivers and streams flow off the land

Precious Cargo The water cycle moves water around Earth. But water—especially fresh water—is unevenly distributed around the planet. You may take running water in your house or school for granted. However, in many places, people must carry their water from fresh sources. In these places, not a drop of water is wasted! Water is a life-giving resource. And the more you know about it, the more you’ll understand why it is important to protect.