The earth is a big, big place. It is filled with millions of plants, animals, people, rocks and trees. The earth has thousands of rivers, streams and creeks and four oceans. As big as the earth, is, however, everything living thing on earth depends on each other to exist in some way or another.
The main thing we need, though, is water. Without water no living thing can exist. But did you know that 97% of the earth’s water is saltwater? That means only 3% of the earth’s water is fresh. That does not sound like much, does it? So where do we get all the water we use for drinking, cooking, swimming, watering the garden and taking a bath?
The water we use for these things comes from the earth—thanks to what scientists call the water cycle. The picture below shows how the water cycle works. We will start with water vapor (air filled with water).
- The sun heats the water found in rivers, oceans and other bodies of water. This causes the water to turn to vapor and float to the sky. NOTE: The salt in salt water is too heavy to float, so all water vapor is fresh water.
- When the water vapor floats to the sky, it rests in the clouds. When the clouds get full, they release the water. This is rain.
- The rain waters the grass and gardens and adds more water to the rivers, streams, lakes and oceans.
- The rain that waters the grass and gardens seeps down into the ground. This ground water feeds the soil and rests in the rocks underground until the sun pulls it out again. And then the process starts all over again.
Are you ready to see for yourself how part of the water cycle works? Let’s get to work!
THINGS YOU NEED
- A clear glass jar-quart-sized works best
- Coffee cup or paper cup
- Aerosol shaving cream (white)
- Blue food coloring
- Large eye dropper (any size will do)
- Turkey baster or spoon
HERE IS WHAT YOU DO
- Fill the clear glass jar two-thirds full of water
- Fill the cup half full of water
- Add two or three drops of food coloring and stir to mix well
- Set the colored water aside
- Shake the shaving cream can as directed and squirt enough shaving cream into the jar to cover the water and come just to the top of the jar rim
- Fill the eye dropper with colored water and begin filling the ‘cloud’ with ‘water vapor’ one drop at a time.
- Count the number of drops you add to the cloud before the cloud gets full and ‘rains’ into the water in the jar.
TRY THIS TOO
- Repeat the experiment using half as much shaving cream as you did the first time. How many drops of water does it take before it starts raining? Is this more or less than the first time you did the experiment? Why do you think the results were different?
- Repeat the experiment using the original amount of shaving cream and using a turkey baster or a spoon to drop the water onto the cloud. What happens?
- Sweep the kitchen floor and gather the dirt and dust into the dust pan. Repeat the experiment using the original amount of shaving cream and the small eye dropper, but in addition to dropping water into the cloud, add some dirt and dust to the cloud. What happens when it rains? Does the dust and dirt fall with the rain?
TRY THIS, TOO
- Once the color swirls settle down, try adding a drop of dish soap somewhere else in the milk. Does anything happen or has all the fat in the milk gathered itself to the first drops of dish soap added to the milk?
- Try the experiment again using a square or oblong pan. Did anything different happen?
- Repeat the experiment with 2%, 1% and/or skim milk. Are the results the same as they were using whole milk? If not, why do you think the results were different?
- Try the experiment using both cold and warm or hot milk. Are the results different? If so, why do you think the results were different?
WHAT YOU LEARNED BY DOING THIS EXPERIMENT
- Every living thing on earth needs water to exist
- Only 3% of the earth’s water is fresh water
- The water cycle is how fresh water is made and used on earth
- Water vapor is water-filled air
- Water vapor lives in the clouds
- Rain happens when clouds get too full of water vapor
- Water in the ground is called ground water
- A thick cloud can hold more water than a thin cloud
- Polluted and dirty water pollutes the ground