Water Flow

In this lesson, students first use paper “land” models to investigate where water goes when it rains on land and then plastic “mountain” models to investigate the cycling of water as heat causes mountain ice to change into liquid water and flow downhill. 

• Maps show us that water is found in different parts of Earth as a solid or a liquid.  
• Liquid water on Earth’s surface flows downhill, pulled by Earth’s gravity.
• Water on Earth doesn’t always stay in the same form. Like all matter, water can change from a solid to a liquid or from a liquid to a gas. It depends on the amount of heat present.

• How do we know where the ocean is on a map? How do we know where the land is on a map?
• How are solids different from liquids?
• Why does rain fall to the ground from the sky?
• How else can we see the effect of Earth’s gravity pulling all things down to the surface?
• What happens to rain once it falls to the surface?
• Why does water flow downhill on both mountains and hills?  
• How does adding heat change liquid water?
• How is evaporation connected to clouds?  
• What causes water to become a solid (ice or snow)? 

Body of water: a part of Earth’s surface that is filled with water

Gravity:  a force that pulls things toward each other

Landform: a natural feature on Earth’s surface

Map: a drawing or other model of an area of Earth’s surface

Water cycle:  the circulation of water from a collection to the atmosphere and back to Earth; includes evaporation, condensation, precipitation, and collection

Solid Water

Ice and snow are both made of water. They are solid forms. Remember that one property of matter is whether it is a solid, a liquid, or a gas. Solids have their own shape. They keep this shape until something changes them by force.

Liquid Water

Oceans, rivers, and lakes are liquid water. Rain is also liquid water. Liquids have no shape of their own. They take the shape of their container. They also flow.

When it rains, liquid water falls from the sky to the ground. It is pulled down by gravity. Gravity is a force that pulls things toward each other. Earth’s gravity pulls all things down toward Earth’s center. Think about throwing a ball in the air. It always falls back to the ground because of gravity.

When rain falls to the ground, some of the water soaks into the ground. The rest of it begins to flow downhill over the land. This means it moves from high places to low places. Gravity pulls liquid water downhill. This is how rivers and streams form.

 

In this lesson, students use models in two different investigations. In the first investigation, students investigate the question: “Where does water go when it rains on land?” In the second investigation, students investigate the question: “How does heat change mountain ice?” Students collaboratively carry out the two investigations to explore where water is found on Earth, the forms that it is found in (solid and liquid in this investigation), and how it changes form and moves over the land when heat is added. In both investigations, students use their models to analyze patterns in where water is found as a solid on Earth and where it is found as a liquid.