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The Leakproof Bag Pencil Trick – Science Project Ideas

Who would have ever thought that a plastic bag, some water, and a few pencils would have adults screaming with fear? learn how to poke holes in a plastic bag filled with water without spilling a drop. Well, that's the theory you're going to test . . . and it's wise to practice your liquid trick over the sink. It's a cool way to learn ...

The Leakproof Bag Pencil Trick – Science Project Ideas

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!

How we did it:

  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?

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