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!

  1. Ages: 5 - 11

  2. <30 minutes

  3. Messy


Step-by-step tutorial

  • Step 1

    Fill the plastic bag halfway with water.

    Photo reference of how to complete step 1

  • Step 2

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

    Photo reference of how to complete step 2

  • Done!

    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?

    Photo reference of how to complete step 3

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