April 27, 2011

Little Explorers: Polymer Power

It's a leak-proof bag!

Here's another little science experiment for you!

Poking Plastic with Pencils

Here's what you need:
  • gallon size zipper bag (Ziploc brand works best)
  • water
  • several freshly sharpened pencils
Fill the zipper bag about 2/3 full of water.  Zip it up.  Hold on tight and push a sharp pencil all the way through both sides of the bag.  Make sure the point of the pencil gets all the way through.  Repeat with all the pencils you have.  You might want to practice over a bucket or sink the first time. 

I repeated the experiment (with a 2nd bag) and had Isabella push the pencils in.  Twice she started to poke the bag and then wanted to put the pencil in a different spot (causing the bag to leak).  So I had her do it fast.  Spear it!

Questions to ask while experimenting:
  • What will happen if I poke a hole in this bag of water?
  • What if I do it again?
  • Why doesn't the water leak out?
  • What will happen if I take out the pencils?
What is happening:

All plastics are made out of polymers.  Polymers are long links of molecules that are usually very strong and stretchy.  When you poke the pencil into the plastic bag the polymers move and stretch (rather than tear) and then seal around the pencil; preventing any water from leaking.

Extreme experimentation:

Do it over an unsuspecting friend's head.    

Notice how Isabella quickly moved her legs because she thought she would get wet.
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