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EASY! 3 Steps to the Perfect Leak Proof Bag Science Experiment

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We’ve done a lot of quick STEM activities. We’ve even done the leak proof bag science experiment before, although we gave it a twist as a brain surgery leak-proof bag!

But this time, we were doing a collection of pencil science experiments, so I knew we needed to add the classic quick science experiment to the list.

So, we gathered some number 2 pencils and got ready to do our leakproof bag experiment!

If you want to do this experiment at home or in the classroom, it is best suited to the outdoors, as the bag does eventually leak when you take out the pencils.

How to do the leak proof bag science experiment! This quick science experiment includes a worksheet to complete the lesson plan.

So, to avoid a huge gush of water on your floor, do it outside!

If you can’t do it outside, you can do the experiment over a large bin to catch any drips.

You may also want to check out our extensive lists of other STEM activities and science experiments for kids!

Leakproof Bag Science Experiment Lesson Plan

Want to turn the leak proof bag science experiment into a complete lesson? Just add these elements to your science time:

A quick and easy science experiment that kids will love! The leak proof bag science experiment teaches the basics of poylmer chains and chemical bonds with ease! #stemed #scieneexperiments #science #kidsactivities

Experiment Variations

Any science experiment should include variations on the “right” answer. For this leak proof bag science experiment, you might try sticking other objects through the bag (like crayons or bamboo skewers) to see which one produces the least amount of leaks.

You can also test the activity with other types of materials. Does the same thing happen when you use a cloth bag? What about a different kind of plastic? Paper?

Science Explanation

Before or after doing the experiment with the kids, have a period where you discuss the science behind the lesson. This is a good resource for exploring the chemistry of polymer chains.  Depending on the age of the children doing the experiment, you can explore the chemistry completely or simplify it.

I did this experiment with my kindergartner, and she was interested to learn the details of the experiment in the section below, but she was not ready for a full high-school level chemistry lesson!

Data Recording and Analysis 

All good scientists know that data recording and analysis is crucial to any scientific discovery. What this looks like will depend on the grade level of the child. A young child might draw a picture of the results and write a word or two.

Older kids can write the chemical formula for polymer chains and analyze what kind of bond each type of material tested has.

No Leak Magic Bag Science Explanation

Amazing magic no leak bag science experiment is an easy science experiment that wows! Use the included lesson plan and leak proof bag worksheet to make teaching a breeze! #science #stemed #stemactivities #scienceexperiment

Do you know why the no leak magic bag works? It’s because of science! Plastic baggies are flexible because they contain long chains of molecules that can bend and flex. If plastic bags did not have polymer chains, the plastic would be hard and inflexible.

But, because these chains are so flexible, when you pierce the bag, the molecular chains in the plastic flex around the pencil inside the hole, creating a tight seal around the pencil and preventing the water from escaping (although you may have a few minor leaks).

When you remove the pencils, the polymer chains can’t move enough to fill the holes, so the water escapes in a fun fountain.

Supplies to Make a Leakproof Bag

You need just a few supplies for the leak proof bag science experiment, which makes it even easier to do!  You’ll want to have one bag for every student and about 4 pencils per student.

You can also have your students do the activity in groups of 3-4.

elementary stem challenge cards

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Pencils and plastic bags for the leak proof bag science experiment

You will need:

Ziploc Storage Bags, Quart, 48 CountZiploc Storage Bags, Quart, 48 CountPencils Pre-sharpened No. 2 144/box 12 Boxes of 12 New Improved EraserPencils Pre-sharpened No. 2 144/box 12 Boxes of 12 New Improved EraserIRIS 53 Quart Stack & Pull Box, ClearIRIS 53 Quart Stack & Pull Box, ClearThe Mason Jar Scientist: 30 Jarring STEAM-Based ProjectsThe Mason Jar Scientist: 30 Jarring STEAM-Based Projects

How to Do the Leakproof Bag Experiment

This experiment is so easy to do!

First, fill the plastic bags with water and seal them tightly.

Girl holding plastic bag filled with water getting ready for the magic no leak bag experiment.

Next, take the bags outdoors or hold them over the bin.

Ask the kids what they think will happen when you put the pencil through the bag. Many of them will think that the bag will leak right away.

Quickly pierce both sides of the bag with the pencil. If you take too long, the bag will leak.

Pencils stuck into plastic bag demonstrating polymer chains in the leakproof bag experiment

Show the kids how the pencil has gone through the bag, but the bag isn’t leaking!

This is a good time to talk about the science behind the lesson.

Pencils stuck through plastic bag filled with water as part of the leak proof bag lesson plan

Ask the kids what they think will happen after you remove the pencil.

Let the kids remove the pencils.

Girl removing pencils from the leak proof bag experiment

The water will escape right away.

Have the kids repeat the experiment with your other materials, and record their results on a science worksheet.

More Quick STEM Activities to Try

Milk Surface Tension Science Experiment

Liquid Density Jar Science Experiment

Cool Science Experiments in Mason Jars

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