Slides in Earth: Our Watery Planet
As the sun heats Earth’s liquid water, it becomes a gas. Later, this gas turns back to a liquid. It falls from the sky to the ground. This happens over and over. This is the water cycle.
Have you ever seen a puddle dry up? ____________ causes the liquid water to become water vapor. You can’t see it, but it’s there in the air.
Water covers most of the Earth’s surface. This is why many people call Earth the water planet. Most of Earth’s water is in oceans. That water is salty. You can’t drink it. You can’t use it to grow plants. People need fresh water to drink, wash, and grow plants.
Most of Earth’s freshwater is frozen. It is in big sheets of ice. These are called glaciers. Earth does have some fresh water in rivers and lakes. There is even fresh water underground. People pump it up to the surface.