Key Concepts
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Water Cycle
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Introduction
You might know that clouds are made of water, but why does it only rain sometimes, and not whenever there are clouds in the sky? This is because the water particles are usually too small to fall to the ground while they are part of a cloud. This experiment will model what is happening when clouds finally start to rain.
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Background
People have been speculating about rain and the water cycle for a long time. There were lots of ideas about where rivers, rain, and oceans came from in many cultures all over the world. The ancient Greeks thought that all land floated on water, while the ancient Hindus described the process of evaporation and precipitation in some of their religious songs. By 1580 CE, an engineer and potter from France named Bernard Palissy is credited with the idea that all rivers can be sourced from rain and snow alone, without water having to come from underground.
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- A plastic cup
- A glass of water
- A slightly bigger jar that the cup can fit into the top
- 5-10 cotton balls
- Thumbtack for poking holes
- (Optional) Food coloring
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Preparation
- Poke several holes in the bottom of the plastic cup
- (optional) add a drop of food coloring to the water
- Place several cotton balls in the plastic cup
- Place the plastic cup in the larger jar
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Procedure
- Make a prediction: When will the water start to leak out of the bottom of the plastic cup?
- Slowly start pouring the water over the cotton balls. Observe what happens.
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Observations and Results
You should see some of the water stay in the jar, until the cotton balls can’t hold anymore and it starts to pour through the holes in the bottom of the cup. This is a good model of what is happening in a cloud. In clouds, tiny particles of water vapor start to condense around dust or dirt particles. As these droplets move around, they get bigger as they bump into more particles, kind of like raindrops on a windshield. When there are enough drops that are big enough, they start to fall to the ground as rain, snow, or hail, depending on the conditions. Obviously, the cotton balls aren’t made of water vapor, but they act as a good model, or example of what is actually going on.
- What would happen if you made the rocket longer? How about shorter?
- How about more fins? Less fins?
- What if you added more weight to certain areas of your rocket?
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Clean Up
Be sure to clean up when you are done. Pour the water down the drain, throw away the cotton balls and cup, and put the other materials back where they belong.
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More to Explore
Try putting your hand on the top of the cup and sealing it while the water is “raining” out of the clouds. What happens? Why is that happening? Is that the same or different than what happens to real clouds? Why?
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Safety First & Adult Supervision
- Follow the experiment’s instructions carefully.
- A responsible adult should assist with each experiment.
- While science experiments at home are exciting ways to learn about science hands-on, please note that some may require participants to take extra safety precautions and/or make a mess.
- Adults should handle or assist with potentially harmful materials or sharp objects.
- Adult should review each experiment and determine what the appropriate age is for the student’s participation in each activity before conducting any experiment.
This experiment was selected for Science at Home because it teaches NGSS Disciplinary Core Ideas, which have broad importance within or across multiple science or engineering disciplines.
Learn more about how this experiment is based in NGSS Disciplinary Core Ideas.
ESS (Earth and Space Science) 2: Earth’s Systems
Grades K-2
- K-ESS2-1. Weather is the combination of sunlight, wind, snow or rain, and temperature in a particular region at a particular time. People measure these conditions to describe and record the weather and to notice patterns over time.
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