What Kids Learn From This STEAM Activity
When kids do the STEAM activity, Pencil through a Bag of Water, they learn that the plastic bag is like a stretchy cover. The plastic bag, because it’s made of special materials called “polymers,” can behave like a stretchy cover. When you push a pencil through the bag filled with water, the bag’s stretchy cover closes around the pencil and doesn’t let water leak out. This shows how the plastic bag, like a stretchy cover, can stop water from leaking. This teaches kids about how things work in science, like how different materials can behave in surprising ways, and it’s a fun way to learn while having a cool experiment!
*What is Polymer?
A polymer is like a long chain made of tiny pieces. Imagine a necklace with lots and lots of beads all linked together. Each bead is a tiny piece called a “monomer.” When you put many of these tiny pieces (monomers) together in a chain, you get a polymer. It’s like building something big from lots of small building blocks, and these chains can be stretchy and strong, which makes them useful for all sorts of things like making plastic bags, toys, and even some clothes.
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What We Need For This STEAM Activity

- Large Ziploc bag
- Water
- 3 Pencils
How to Do the STEAM Activity, Pencil Through A Bag Of Water Experiment
- Fill a plastic bag with water, but not too full.
- Seal the bag tightly so there’s no air inside.
- Push a sharpened pencil through the bag. Do the same for the other two pencils.
STEAM Activity Pencil Through A Bag of Water – Put A Sharpened Pencil Through The Bag - Observe that the bag doesn’t leak, even with the pencil inside.
- Have fun exploring why this happens!
STEAM Activity Pencil Through A Bag of Water STEAM Activity Pencil Through A Bag of Water – Water Comes Out When You Take The Pencils Out
Variations & Challenges
- Challenge kids to explain why the bag doesn’t leak when the pencil goes through it. What’s happening with the plastic and the water?
- Before doing the activity, make predictions about what will happen. Will the bag still hold the water? Then, test your predictions by doing the experiments.
- Put one plastic bag inside another, both filled with water. Try pushing the pencil through both bags. Does it still work?
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