Saturday, November 21, 2015


The Secret of the Leak-Proof Bag Science Experiment

Sometimes you need a quick science experiment that is both simple and stunning, and that all kids, from preschoolers to teens will enjoy.  This leak-proof bag is it!

It takes less than a minute to prepare, and kids of all ages love it!  It is a science experiment that can double as a science magic show, and everyone wants to know how it works.  

I love holding up a bag full of water and asking children what will happen if I poke it with a sharp pencil.  Sometimes I follow with a wink and a grin and say, "What if I hold it over your head and poke it?!"

To do the leak-proof bag experiment you simply fill a zip lock bag about 2/3 full of water.  Carefully poke a sharp pencil right through the water and out the other end.  No water spills!  Try it with other sharp objects--my son likes using kabob skewers!  

So, what's the secret?  Zip-lock bags, like other plastics, are made from polymers--long chains of molecules.  When you poke through the bag, you force the polymers apart, but they quickly press back as much as possible.  As they press towards the pencil, they practically seal the hole you made.

Now, your pencil can always wiggle more space between the pencil and the bag, so you may want to practice over a sink before you do it over your kiddos' heads!

When you're done, hold the bag over the sink and pull the pencils out.  These "fountains" are just as exciting as the leak proof bag!!

Do you love science?  Be sure to check out my 100+ Science Experiments/Activities!!

And enjoy these other activities from the STEM Saturday Crew:

Edible Igneous Rocks and other fun from The Usual Mayhem
Post-Thanksgiving Turkey Anatomy from Suzy Homeschooler

I may share at any of these parties!

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shelah moss said...

What an easy science experiment. It is sure to amaze the kids!

Carla at Preschool Powol Packets said...

Yes! It's easiness and Wow! factor make it a winner!