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Exploding Pumpkins

Hey Friends! Happy Thursday! I'm so excited to have Kimberly from Team Cartwright guest posting about a really fun Halloween project.... Exploding pumpkins!! So fun! You can find me at Mamas Organized Chaos sharing a strategy for handling big emotions in our kids. 

Halloween is a great time of year to work on some STEM with your kids.  Things are spooky, icky, sticky, and sometimes a little gross.  Perfect for some easy chemical reactions.  I love that you can do some of them in a pumpkin.  Festive and easy clean up!  That is exactly what we are doing today- making lava spewing pumpkin.

I've made easy no mess volcanoes in the past, and they are always a big hit.  Seriously, I never get tired of doing it and I haven't found a child that has either.  But I did want to try doing it a bit differently.  We went with the hydrogen peroxide method, also known as elephant toothpaste.  (It's called elephant toothpaste because of the thick foam it can make.)


You need a few ingredients for this one, most of which you probably already have.
  • 2 TBSP warm water
  • 1 tsp yeast
  • 1 small pumpkin
  • 1/2 cup 6% hydrogen peroxide
  • 4-5 drops food colors
  • a squirt of dish soap
We had almost all of these, I did have to send Pat out to grab some hydrogen peroxide.  A note on that- the typical peroxide found in stores is only 3%.  This is still usable.  You will need to add a bit more, and the foam won't be as thick.  But I like to just use what we have, so we went with it.  (You can always order some 6% if you want it to be really foamy!)


Here is how to put it all together.
  1. Prep your pumpkin for carving like normal.  Even carve in the face if you want the foam to ooze out that way!
  2. Mix the yeast and the warm water, and let it sit for a few minutes.
  3. While the yeast and water sit add the hydrogen peroxide, food coloring, and dish soap to the pumpkin and mix together.
  4. Pour in the yeast, put on the top and watch the foam rise!

Safety and Clean Up

Put the pumpkin on a baking sheet or some other container to help with the clean up.  This reaction is pretty safe, but with all things like this, keep an eye on your kids so they don't get any in their eyes or mouths.  The reaction can be slightly exothermic, meaning it can get hot, especially if you use the 6% hydrogen peroxide.  There isn't anything I would consider unsafe here, but I would do this one with adult supervision.  (Although I think anything involving food coloring needs adult supervision.  No stains!)

What's Going On

For toddlers and preschoolers, just knowing this a chemical reaction is taking place is often enough of an explanation.  But if you are doing this with older kids they might want to know a bit more.  Hydrogen peroxide breaks down into water and oxygen.  The yeast acts as a catalyst to speed up this reaction.  The soap traps the oxygen as it is produced making bubbles so we can see it.  This is the foam that is formed.  The food coloring just makes it cooler looking.

The Reaction

2H2O2 --> 2H2O + O2
This is what is called a balanced equation for the reaction.  Don't worry, I won't go too deeply into it, but basically, it says that two hydrogen peroxide molecules will yield two water molecules and one oxygen molecule.  It is exothermic, which means it produces heat!

After the Explosion

You can add a bit of art into this project by using the pumpkin top as a stamp!  The food coloring makes it fun to create a picture with the foam.  It will dry and leave some color.
After the explosion, I rinsed out the pumpkin and I am happy to say it is still just fine, even a week after the reaction.  So doing this doesn't mean you have to waste your pumpkin.  If your child wants to learn more about what is happening you can check out these references:

Happy Sciencing!

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