Mix up a bubbly brew in a potions lab fit for any little wizard or witch with an awesome Halloween chemistry experiment and science activity. Super simple household ingredients create a cool Halloween themed chemical reaction that is just as much fun to play with as it is to learn from! Create a season filled with clever, spooky, creepy learning opportunities with our 31 days of Halloween STEM Countdown!


Simple Elephant's toothpaste with a Halloween chemistry experiment for kids with wizard's brew! Set up a hydrogen peroxide and yeast exothermic chemical reactions and Halloween science activity for your little wizard or witch! Halloween chemical reactions with simple household supplies make learning fun. The perfect Halloween science experiments for kids to try at home or to do in a classroom.

This fall season we are exploring some cool Halloween themed chemistry experiments. This exothermic chemical reaction using hydrogen peroxide and yeast is lots of fun and super easy to set up.

Although a bit messy, it also has a terrific sensory play element built right in. Make sure to check out our zombie slime for more cool Halloween chemistry science experiments.

KICK THE SEASON OFF RIGHT! 31 Days of Halloween STEM Countdown.

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The reaction between the hydrogen peroxide and the yeast makes this awesome foam that is perfectly safe for little hands to play with and a breeze to clean up. This is NOT edible! We love cool fizzing, foaming, erupting chemistry.

Check out the awesome photos below and at the end, you will see everything you need to make your own Halloween hydrogen and yeast experiment.

Halloween Chemistry Experiment for Kids

One of the best parts of this Halloween chemistry experiment is the opportunity for tons of hands-on play and exploration. This hydrogen peroxide and yeast science activity encourage kids to explore the reaction with their hands!

This classic chemistry experiment is often called elephant’s toothpaste because of the voluminous amount of foam that it usually produces. However, you do need a much stronger percentage of hydrogen peroxide to produce that reaction.

You can still enjoy the same type of chemistry experiment but with less foam and less of an exothermic reaction with regular household hydrogen peroxide. The experiment is still awesome, and if you get a chance to try the higher percentage of peroxide, it will be worth it too.

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Exothermic Halloween Chemistry Experiment for Kid Science

We love the seasons/ holidays here, so it’s fun to give our classic science experiments the theme of the holiday we are approaching. Right now we are getting excited for Halloween! So Halloween themed science and chemistry it is!

CHECK OUT: Halloween Slime {with a video!}

Food coloring is a super simple way to give science a holiday theme. My son is also very generous with his food coloring use. The simple stuff from the grocery store works just fine.

Plus you can easily pick up the other ingredients on your next shopping trip. Check your cabinets first. That’s the best part of kitchen science.

Wizards Brew Chemistry Experiment and Halloween Chemical Reaction Activity for Kids


The reaction between the hydrogen peroxide and the yeast is called an exothermic reaction. You will feel warmth to the outside of the container because energy is being released.

The yeast helped to remove the oxygen from the hydrogen peroxide creating tons of tiny bubbles that made all that cool foam. The foam is just the oxygen, water, and dish soap that you added.

If you pay close attention, the reaction continues for quite a while and looks quite different depending on the size of the container you use! Experiment with different sizes! We chose three different size flasks for our wizard’s brew. Each one looked pretty cool.

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Halloween Science Activity with a Halloween Chemistry Experiment


  • Hydrogen Peroxide
  • Warm Water
  • Yeast Packets {we used two packets for the three beakers}
  • Flasks or Plastic Bottles
  • Teaspoon and Tablespoon
  • Food Coloring
  • Dish Soap
  • Tray or Container {to place bottles or beakers on to catch foam}
  • Small Cup {mixing yeast and water}


Pour the same amount of hydrogen peroxide into each container unless you are just using one container. We used a 1/2 cup.

Squirt dish soap into flask or bottle.

Add food coloring {as much as you like, my son is very generous}.


Mix 1 teaspoon of yeast with 2 tablespoons of warm water. It was clumpy and didn’t mix perfectly but that’s fine!

Pour the yeast mixture into the container and check out what happens. Notice how quickly the reaction begins. The foam had started before he was even finished pouring in the rest of the mixture.

For the larger flask, the reaction continued for quite a while inside the beaker before it came out of the top. Would a different amount of hydrogen and yeast change that?

See him adding the hydrogen below.

Halloween Chemistry Experiment : Pouring Hydrogen Peroxide

Next, he’s adding dish soap and then food coloring. You can swish a little to combine color.

Halloween Chemistry Experiment : Adding Dish Soap

Now mix up your yeast and water.

Halloween Chemistry Experiment : food coloring

Pour it in!

Halloween Chemistry Experiment : Adding yeast and water mixture to hydrogen peroxide

Now, this isn’t like a baking soda and vinegar chemical reaction where the reaction is more instantaneous. This takes a little bit longer, but at least you get plenty of time to observe the changes.

You can see we are using our smallest flask for some of our Halloween chemistry experiment above and below. Because it’s the smallest, it happens to be the most dramatic.

However, make sure to notice what happens with the large flask. Although not super dramatic, it looks pretty cool.

Watching Halloween chemistry experiment and exothermic reaction happening

And for the grand finale, foam everywhere. Remember I said to take a look at the large flask? Notice the difference?


Go ahead and play around with the foam. My son added additional red food coloring. This will temporarily stain the hands if you use as much as my son! If we stayed with the pink foam this would not have happened.

You can also go ahead and whip up new yeast mixtures and add it with extra hydrogen peroxide to the already foamy bottles or flasks. We always do this with our baking soda and vinegar reactions!

Playing around with hydrogen peroxide and yeast has been a new kind of chemistry experiment for us this year. We usually use the classic baking soda and vinegar experiments for many of our themed science activities. Time to try new things!


We always have a ton of stuff going on around here no matter what the season or holiday. Click on the pictures below for more!