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Science for Kids: Baggie and Pencil Magic

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Here’s a fun science activity for kids of all ages! What happens when you put a sharp pencil through a baggie filled with water?

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baggie and pencil header

 

Baggie and Pencil Magic Science Activity

Materials for Baggie and Pencil Magic

  • plastic baggie
  • sharp pencil
  • water

 

Procedure for Baggie and Pencil Magic

  1. Fill a baggie about 3/4 of the way full with water and seal it shut.
  2. Make sure your pencil is sharpened. (The sharper the better!)
  3. Hold up the baggie with one hand and use the other hand to firmly push the pointy end of the pencil through the side of the bag. Continue pushing it until the point is also coming out the other side of the bag.
  4. Observe what happens!

 pencilbaggie

Question to Spark More Curiosity & Critical Thinking

Is this what you expected to happen? Why or why not? What do you think will happen when the pencil is pulled out of the baggie?

What’s Going On?

No water spills out the holes because ziploc bags are made of a polymer. Polymers have long chains of molecules that are flexible. When you poke a sharp pencil through the baggie,  the pencil slides in between the chain of molecules that make up the polymer. The molecule chains make a seal around the pencil that won’t let the water out.

Want to go even further?

Even more activities to inspire creativity and critical thinking for various ages:

    • Can you put more than one pencil through your baggie at a time?
    • Try this experiment with other materials.

magic baggie and pencil science trick for kids

 

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Comments

  4. Cool experiment and you are so brave to do it in the living room. I think my 9 year old son would squeeze it to see what happens next.

    Reply

  5. This is such a fun activity, I’ve been meaning to do it with my kids, maybe we’ll do it this summer when we’re between curriculum.

    Reply

    • Thanks, Ticia! The best thing about this science demo is there is such little prep. It would be really fun to do outside on a warm day. When you pull the pencils out, you’d have a little fountain!

      Reply

  13. The polymer bag doesn’t really “seal” the hole around the pencil. Actually, the water doesn’t leak out because of air pressure. A little water leaks out when you poke the hole in the bag. If the top of the bag is sealed, more air can’t get inside it and as the water level falls a bit, it lowers the pressure of the water inside the bag as the air expands into the new space. At some point, the total pressure of the water and air inside the bag equals the air pressure outside the bag (and surface tension of the water).

    A similar experiment can be done with a plastic bottle with a lid. Use a pin to poke 6-8 holes all around the side of the bottle. As long as the lid is on, the holes won’t leak. Have an unsuspecting person unscrew the lid, however … watch out!

    Reply

  14. I tried this experiment today with my summer camp friends from age group 6 year old to 12 year olds. They loved it! We put 10 pencils through the one bag and they were totally amazed that it did not leak.

    Reply

  16. Just discovered your site. When we tried the pencil in the baggie, it actually leaked. I followed the directions exactly and used Ziploc baggies. Not sure why?

    Reply

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