Water Wonders

How do you clean up dirty water?
Not with soap! You need a filter, a device that removes impurities, like dirt, from water. The filter you’ll make here—with the help of an adult—is a super strainer, and it’ll help you clean up your act.

You'll need:

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1. 2-liter plastic bottle, empty and clean

2. Utility knife

3. Dirty water (make your own with stuff like coffee grounds, dirt, crunched-up old leaves, cooking oil, or tiny pieces of foam)

4. Measuring cup

5. Spoon

6. Stopwatch or clock with a second hand

7. Pencil and paper

8. As many of the following filter materials as you can get:

• Activated charcoal (available in the fish section at a pet store)

• Gravel

• Sand (coarse and/or fine)

• Cotton balls

9. Coffee filter (a bandanna, old sock, napkin, or paper towel works, too!)

How Things Work-Water Wonders
How Things Work-Water Wonders
How Things Work-Water Wonders

Your filtered water is still not clean enough to drink, but a plant would love it!


The slower, the better! The longer it takes for water to move through a filter, the cleaner it gets. Water slips easily through the filter materials, but bigger gunk, like dirt, gets trapped. The filter materials usually get finer and finer, so they can catch whatever was missed earlier. Activated charcoal can be near the end of the water’s path, because it uses an electrical charge to grab particles too small for us to see.

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