Pencil Trick

Pencil Trick

As your family gears up for back-to-school season, use some of your newly bought goods to test out a cool effect! With just three simple materials you can find at home,  you'll be surprised with what they can do!

5 - 9
Est. Time:
<30 mins

How we did it:

Materials List

  1. plastic zip bag
  2. round pencils - with sharp tips!
  3. water
  1. Fill the plastic bag halfway with water.

  2. Use one hand and hold the plastic bag at the top for stability.

  3. Use a pencil to quickly pierce the bag and water!

    What's going on?

    Most plastic bags are made of polyethylene, a polymer that is durable, flexible, and shaped like long strands.  When the pencil is quickly pierced into the bag of water, the polyethylene molecules separate but don't break, forming a seal around the pencil. If the pencil is pierced into the bag before the water is put in, the water will leak!  

    Try the experiment with a faceted pencil, a larger pencil, or a thicker plastic bag. What happens?