Monday, March 4, 2013

The Exploding Lunch Bag

We all like explosions, right?  So science experiments where something explodes are especially fun.  Not too long ago my daughters and I did the Exploding Lunch Bag experiment from Science Bob's website.  It's relatively simple and isn't dangerous, despite the exploding part.  Most of the ingredients you probably have in your house already.

Simply take a small zip-lock lunch bag.  It's important to find a small bag.  The bag may not explode if it is too large.  Pour in a 1/4 cup of warm/hot water and 1/2 cup of vinegar.  Then wrap 3 teaspoons of baking soda in a tissue.  Now take the bag and tissue full of baking soda outside.  You can do this in the house, but it may make a big mess.

Very quickly dump the baking soda filled tissue in the bag.  Quickly seal the bag and walk away.  The baking soda will begin to react with the fluid.  You should see the bag expand, and then eventually pop.  My wife took a video of me getting the bag ready.  A warning, however.  I'm wearing lounging pants because, hey, it's a Sunday afternoon and Sunday afternoons are for lounging!  Second, I'm wearing sandles with socks.  Yes, I know you're not supposed to do this, but my sandles were the closest pair of shoes when it was time to do the experiment.  Forgive me for this fashion failure!

At the end the video jerks.  The pop from the lunch bag, which you can hear, scared my wife and she jumped.  Hence the jerky video.  :-)

As you can see from the picture, the zip-lock seal holds, it's the plastic bag that rips open.  So what's going on here?  Why does the bag pop open?  When the baking soda and vinegar mix, there is a reaction that creates carbon dioxide gas.  The tissue is used so that the baking soda doesn't immediately react when you dump it in the bag.  This gives you time to seal the bag.  The carbon dioxide gas takes up space, so the bag expands.  But the bag can only expand so much.  Eventually the gas puts enough pressure on the bag that it pops.  Fun stuff!

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