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Leak-Proof Bag

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Supplies
  • Water
  • Sharp Pencils or Colored Pencils
  • Plastic Bag
Instructions:
  1. Make sure your pencils are all sharpened.
  2. Add water to your zip-lock plastic bag and close it tightly.
  3. Stick your pencils through the bag and see what happens! (Tip: Try this outside or over a bucket in case of an accident.)

Age Adjustments
  • Younger Children:
    • Have an adult poke the pencils through the bag, and task your child with pulling them out.
    • Keep your plastic bag over a bucket and play in the water that comes out of the pencil holes.
  • Older Children:
    • Test to see if this experiment works with liquids other than water.
    • Grab some sharp colored pencils and colored sharpies. Draw different colored circles on the bag with the sharpies and turn this experiment into a color-matching poke game!
    • Try this experiment with dull pencils. What happens?

Why Does This Happen?

Plastic bags are made up of long chains of molecules called polymers.

Polymers are what makes a plastic bag stretchy. When the sharpened pencils pierce through the bag, these long chains of molecules seal around the pencils within seconds, thereby preventing a leak.


Support the Museum

The Virginia Discovery Museum is a vital nonprofit community resource, but we will be closed through at least July 31 due to the COVID-19 pandemic. Please consider a donation to support us during this uncertain time. Donate Now