The Mystery of the Self-sealing Sandwich Bag
February 21st, 2009 . by Joyce
Hosted by Cecily and MamaGeek
Our twelve-year old son is learning about molecular structures in his seventh-grade science class. I should be asking him about this experiment before posting, but he is out sailing with his dad right now, so I’ll have to try to remember what he said. (Though it’s Saturday morning, I’m posting this as a Photostory Friday.)
Here’s what you do.
First of all, fill a sealable plastic sandwich bag with water.
Next, poke a sharpened pencil quickly through the bag.
The puncture should pull tightly around the holes, preventing any leaking. We left this bag for hours, and it still had not leaked.
Can you guess the reason for this? As I recall, it has something to do with how long the molecular chains are for polymers (plastics). Since the long molecular chain is bound strongly together, it sort of tightens up around the hole.
When our son gets home, I’ll have him take a look at this post to see if I’ve remembered correctly.
See if this works for you!
That is really cool. We’ve read about it, but we’ve never done it. I wonder if there’s a science experiment in there somewhere? *sigh*
Wow. I’m going to have to do this with my kids. Even if they don’t get the scientic explanation!
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I remember doing this with my older kids. Time files and I forgot all about this. However, Rachel “invents” these kinds of experiments all the time so I rarely have to “teach” science experiments to her. I’m sure up in her room somewhere there is a bag of water with a pencil sticking out and a clock to measure the time lapse. She’s a funny one. (Oh and she would surely know the scientific properties involved that interest me almost zero — a chip off Dad’s block.)
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That is so cool! I’m sure your son had fun with it. I hope you are having a lovely weekend!
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I never knew that about plastic baggies! I’ll have to try that experiement! Hope you’re having a lovely day.
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That is so cool!!
Guess what I’ll be doing with Cameron when he gets home from school this afternoon.
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This is very ‘kewl’ …
I’m not quite sure why it works either, but it’s fascinating and I may give it a go myself … just because. Thanks for sharing. Hope your back is better ;–)
Hugs and blessings,
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Wow! I’m impressed. And it would be a very impressive trick in the classroom!
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That is soo cool!! My five year old would be thrilled if I do that trick at home!!