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Science Rocks!

Water Filter Part II


your results

Sent in by:
Helen of Cape Coral, FL

Filter out how to survive on a deserted island.

Materials Needed

  • pitcher of water
  • dirt
  • salt
  • scissors
  • gravel
  • sand
  • cotton (like cotton balls, a bandana, or an old sock)
  • cups
  • scissors



  1. Check with a grown-up before you begin.
  2. If you were on a deserted island, how could you turn dirty, salty water into water that you can drink?
  3. The ZOOMers tried it by making a water filter out of natural materials like sand, gravel, and cotton. You can try it, too.
  4. Before you build your filter, mix up some dirty, salty water in a pitcher.
  5. Then use cups to build a filter that will filter out most of the dirt using sand, gravel, and cotton. Can you filter out the salt too?
  6. Use the Saltwater Tester to see if you got it all out.

Ready for the science scoop on how water filters work? Water is made up of very small particles called molecules. Each water molecule is made of two hydrogen atoms and one oxygen atom. That's why water is called H2O.
When water is first poured into the filter, some of the water molecules stick to the gravel, sand, and cotton and get them wet. Once the filter is wet, the rest of the water molecules slip through the spaces in between the gravel, sand, and cotton. The dirt particles are bigger than the water molecules, so they can't get through. They get stuck in the filter. How could you redesign your filter to work better? Do different types of fabric filter better than others? Test it out, and send your results to ZOOM!

Some of your Results

Sarah, age 11 of Pearland, TX wrote:
It worked so well! I did it for a science project, and it worked perfectly, and the water came out crystal clear!

Sammie, age 7 of Brampton, Ontario wrote:
it came out dirty th first time but the seond time I bulit the filter better so the water was cleaner

Chanis, age 11 of Gainesville, FL wrote:
at fist it was black but then I tried it again and it came out clear. I almost wanted to drink it.

Audrey, age 13 of Jacksonville, NC wrote:
This was soo helpful to me. I did it with my classmates and it was best!

Aira, age 11 of Manila wrote:
i was confused at it first but when I asked my dad I got it.

Diana, age 11 of New South Wales, Australia wrote:
When I did it, it was so amazing. It almost looked crystal clear! Thanks for the great ideas.

Karan, age 14 of Brampton, ON wrote:
the filter didn't. maybe because I did something wrong.

Ray, age 8 of Brooklyn, NY wrote:
It was really confused in the begining because I did not know where to get the supplies so I tried the hardware store for the buzzer than I went to the pet shop for the sand. After I got my supplies ready I did it the first time and it was so amazing, I filtered the dirty mud water to clear water. The best part is that I did it with my brother and four year old cousin and it worked!!!

Leon of Toronto, Ontario wrote:
This awesome water filter made the water so pure.

ZOOM Fan, age 16 of Hawthorne, CA wrote:
It was coooool! I thought that I should have taken a sample of the water before the filteration and one from after and compare them.

Brittany, age 13 of Fitchburg, MA wrote:
it worked so great the water realy came out clear well were doind this for a science test

Kayla, age 9 of Greenville, NC wrote:
The water came out clear!

Niki, age 13 wrote:
Thank you!! In sciene we had this contest thing, and well we had this poluted water. We had to make it drinkable, and this helped me decide on what to do and how to make the filter! Thanks

Ashley of Nova Scotia wrote:
i dont understand how to create the filter? put rocks, sand, ect in a cup?

Zack, age 9 of Berwick, ME wrote:
The water turned clear it was awesome

Jamie, age 9 of Mesa, AZ wrote:
actuely I did it in school and it was awsome im going into 5th grade

Elise, age 10 of Norfolk, MA wrote:
It came out kind of clear. I didnt drink it.

Tori and Bity, age 13 of Fargo, ND wrote:
We had to do this for I and I in school. It worked great thanks for the idea.

Jalil, age 12 of Philadelphia wrote:
When I poured the water and oil through the sand the water came out crystal clear and all the oil stayed on top of the sand. I't was cool

Emily, age 10 of Ontario wrote:
I did't have all the suplies needed so,,,, I took a cup and put some filter paper over the top. I didn't have any gravel so I used beeds insted, I put the beeds on so that they were spred out over the filter paper. Then I placed the the cup in a bowl so that it wouldn't make a mess because some of the dirty water would go over the sides. When I checked the bottem of the cup the water was clean! I would probaly NOT drink it though!

Salena, age 13 of Fontana, CA wrote:
i changed it up a it I combied all three materials and it worked okay.

Bayan, age 14 of Oak Lawn, IL wrote:
It was about 2 years ago when I seen this experiment. I did it for my science fair project in 6th grade and I won OUTSTANDING!!! I was so amazed. I changed it up a little bit. Here are the things I did not use: sand old socks or scissors or cotton this is what I used, I used a bandana VINIGAR! Also everything else but instead of scissors I used a nail to poke holes in the cup. Vinigar was the main ingreadiant I acually worked better than the sand. you should try it but do not drink the dirty water!!

Ali, age 10 of Gahanna, OH wrote:
The cotton balls made a trap for everything so it was clear healthy water

Salvador, age 16 of Juno, AK wrote:
I struggled at first, but then clean water came out!!!

Farah, age 12 of Halifax, NS wrote:
It worked great!! I used cotton balls, filter paper, gravel and sand in that order and the water became so clean and pure I used it for my science fair!

Madisyn, age 9 of Emporia, KS wrote:
It got clear and drinkable!

Lucas, age 11 of Saratoga, CA wrote:
The water was completly pure! I asked my dad to see iff it was completely pure but he said there were some microscopic bacteria left and I shouldn't drink it.

Casie, age 11 of Philadelphia, PA wrote:
It turned out clean!!!

San'Tiece, age 13 of Owasso, OK wrote:
The project was cool! It really worked! The water was very clean and clear!

Annie, age 15 of St. Bruno, QC wrote:
Hey, In my science class at school, we are learning about water purification systems, and I have some advice for you guys. Don't drink the water!! Even though it looks clear and clean, there are still microscopic bacteria in the water that can't be filtered out. The water can get you terribly ill.

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