Free Pumpkin Science Experiment: Chemistry in Action

There are a lot of fun ways to use your fall pumpkins as we near the end of the season. One option sure to delight is the classic “Elephant’s Toothpaste” volcano experiment. Here’s how we worked through this fun activity!

Aside from your pumpkin, which is fun to carve ahead of time, you will need hydrogen peroxide, dish soap, yeast, and food coloring (for fun).

You can adhere to strict measurements of the hydrogen peroxide (1/2 cup) and yeast (1 tablespoon yeast mixed with three tablespoons of water). But, since I have a 12-year-old son, we think it’s more fun to just dump a bunch of both substances in and make the biggest reaction we can.

We also had a very large pumpkin to work with, so in order to experience the drama of elephant toothpaste, we used the entire bottle of hydrogen peroxide and a full packet of the Active Dry Yeast. Squeeze in a hearty dose of liquid dish detergent, add a few drops of food coloring for some flair, and watch your big volcano moment happen!

Steps to follow:

  • Place a cup with your hydrogen peroxide and a hearty dose of liquid dish soap inside the pumpkin.
  • Then, mix the yeast with warm water in a second cup, and pour the yeast into the hydrogen peroxide cup.
  • Watch the fun happen!

And then, because we wanted our reaction to be even bigger and better, we just dumped the rest of everything into the pumpkin.

So what is the science behind this reaction?

Hydrogen Peroxide is made from hydrogen and oxygen atoms. Over time, this solution will break down into oxygen gas and water on its own. By using the yeast as our catalyst, we can speed up this reaction. The dish soap adds the surface tension needed to trap the oxygen gas and make it more visible as it escapes.

A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing a permanent change. Based on this definition, ask your students if they can think of any other common household items that could act as a catalyst. Enzymes in laundry detergents and dish washing detergents act as catalysts, for example. And, in fact, if you have been working through our Science with Friends Anatomy Bundle, you could also point out that there are enzymes in our digestive system that act as chemical catalysts!

After joking about brushing our own teeth with our concoction, we decided to toss our old pumpkin into a corner of our backyard, where we will see if we can spot any new pumpkin vines next year!

Nicole Paitsel is the creator and co-founder of Learning with Friends. She is a a former classroom teacher and current homeschooling mom of two. If you can’t find her, look in the local used book store where she is probably hunting for treasures.

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