Make a Water Cycle Model
Earth is a planet full of water. 70% of its surface is covered with water in oceans, lakes, rivers, and more. Water on our planet can also be found in the atmosphere and underground. In this lesson, students will explore how water is continually cycled among land, the oceans, and the atmosphere. As students build a physical model of the water cycle, they will be able to simulate and observe evaporation, condensation, precipitation, and other water cycle processes in real-time.
Remote learning: This lesson plan can be adapted to work remotely. The Engage section of the lesson can be done over a video call. Students will need to do their water cycle model experiment individually and independently during the Explore section using the Student Worksheet as a guide and can then share their observations with each other, virtually. A set of materials can be prepared in advance or students can use materials found around the house. End the lesson with a discussion over a video call during the Reflect section.
- Explain how water is cycled among land, the ocean, and the atmosphere.
- Describe at least five processes within the water cycle.
- Understand how the Sun and gravity drive the water cycle.
NGSS AlignmentThis lesson helps students prepare for these Next Generation Science Standards Performance Expectations:
- MS-ESS2-4. Develop a model to describe the cycling of water through Earth's systems driven by energy from the sun and the force of gravity.
|Science & Engineering Practices||Disciplinary Core Ideas||Crosscutting Concepts|
|Science & Engineering Practices||Developing and Using Models.
Develop a model to describe unobservable mechanisms
||Disciplinary Core Ideas||ESS2.C: The Roles of Water in Earth's Surface.
Water continually cycles among land, ocean, and atmosphere via transpiration, evaporation, condensation and crystallization, and precipitation, as well as downhill flows on land.
Global movements of water and its changes in form are propelled by sunlight and gravity.
|Crosscutting Concepts||Energy and Matter.
With a natural or designed system, the transfer of energy drives the motion and/or cycling of matter.
For educator and each student group of 3–5:
- Transparent plastic box with transparent lid, such as a plastic storage or shoe box.
- A rock or stone with a diameter of about 3–4 in.; alternatively, modeling clay can be used to shape a mountain.
- Natural sand or soil, about 2 cups
- Water, about 500 mL. Note: You will be able to see evaporation happening more quickly if you use warm or room-temperature water.
- Heat lamp or a lamp with an incandescent light bulb
- Ice cubes, 1 cup. It might be good to have extra ice cubes on hand in case they melt too quickly and students need to replace them.
- Re-sealable plastic bags, snack-size (2)
- Timer or clock
- Scissors (for educator only)
Background Information for TeachersThis section contains a quick review for teachers of the science and concepts covered in this lesson.
Earth is a planet full of water. About 70% of the Earth's surface is covered by water, but water is not distributed equally on Earth. 97% of the water is found in the world's oceans; the remaining water is found in glaciers and ice, rivers, lakes, underground, or in the atmosphere. The U.S. Geological Survey (USGS) estimates that Earth's total water supply is about 326 million cubic miles (about 1,359 million cubic km) of water! Most of this water is liquid, but on Earth water can also exist as a solid in the form of ice or snow, and as a gas in the form of water vapor.
The water on Earth is in constant movement. This movement is not limited to Earth's surface, but also includes the atmosphere and the subsurface. The water cycle, also called the hydrologic cycle, describes how water moves within and on Earth and atmosphere and its transition from one state to another. The water cycle is dynamic and involves many different processes that contribute to water being moved from one place to another. Some of these processes are evaporation, condensation, precipitation, transpiration, and infiltration (Figure 1).
A cross-section of a landscape including an ocean, green land, and snowy mountains. The sun is shown above the ocean. Clouds are shown above the land and the ocean. Blue areas depict rivers and lakes on the green land. Grey arrows show the movement of water from the ocean into the atmosphere, back onto the land and within the subsurface. Blue arrows visualize processes such as evaporation, transpiration, surface runoff, or infiltration. Blue dashed lines from the clouds to the ground visualize precipitation.
Figure 1. Schematic diagram of the water cycle. (Image credit: Water_Cycle_-_blank.svg: *Wasserkreislauf.png: de:Benutzer:Joooo derivative work: moyogo (talk) derivative work: Alexchris, CC BY-SA 3.0 , via Wikimedia Commons, image was edited to include transpiration and arrows for infiltration and surface runoff.)
The Sun is the major driver of the water cycle. Surface waters such as the ocean, lakes, and rivers are heated up by solar energy and thus, some of the liquid water evaporates and becomes water vapor. As warm air rises, that moist air rises to higher altitudes. In the process, it cools down and eventually condenses into water droplets. This process is called condensation. We see these tiny water droplets as clouds in the sky. The tiny water droplets within a cloud merge and become bigger and heavier until they get too heavy and fall down to the ground due to gravity. This process is called precipitation. If temperatures are too cold to keep the water droplets in a liquid state, they crystalize and form snow or ice crystals and fall to the ground as snow or hail. Snow that is deposited on mountains or glaciers can be stored as solid water for thousands of years until it gets warm enough for it to melt again. Ice and snow can also directly transform into water vapor in a process called sublimation. Gravity also causes liquid water to fall on land, and thus get absorbed into the soil through infiltration where it can be stored as groundwater or taken up by plants. Plants release some of the water back into the atmosphere through their leaves in a process called transpiration. Water that does not soak into the ground flows over the land as surface runoff until it enters a river, lake, or the ocean. Again, gravity is the driving force. These water bodies function as storage reservoirs for liquid water. It is from there that the water cycle starts again when the Sun's energy turns the water into water vapor.
The horizontal movement of water in the water cycle happens both in the atmosphere through clouds being moved around the globe by air currents, and through water flow on land as surface runoff or as waterflow in rivers or underground. Although water in the water cycle is constantly moving and continuously transforming from one state to another, no water ever disappears! The water that exists on our planet today is the same water that existed on our planet a thousand or a million years ago! The natural cycling of water is one of the most important processes on Earth, as it provides all living organisms with a continuous supply of fresh water. The water cycle also plays a significant role in the weather patterns on our planet, as it contributes to weather events such as precipitation or cloud formation. Without the water naturally recycling itself, life on Earth would not be possible!
In this lesson, students will explore some of the processes that are part of the water cycle in more detail. They will build a miniature landscape, including a water body inside a closed plastic box, and then use a heat lamp to mimic the Sun. In their model, students will be able to observe evaporation, condensation, precipitation, infiltration, and surface runoff in real-time. Based on their observations, students will be able to conclude that the water cycle is propelled by the Sun and gravity.