Learn about exothermic reactions, catalysts, chemical reactions, and color mixing with this fun and simple rainbow science experiment! Perfect for a unicorn-lover who wants to make magical rainbow unicorn toothpaste or for a rainbow-themed playdate or classroom party. This is jaw-dropping fun that will amaze kids and adults alike!
At the end of this post be sure to check out over one dozen more rainbow learning activities the kids will love!
Awesome Science Experiments for Kids
*This post contains affiliate links. Please see our disclosure policy.
If you enjoy this rainbow science experiment you are going to LOVE my new book, AWESOME SCIENCE EXPERIMENTS FOR KIDS. It contains over 100 colorful and creative STEAM activities for kids ages 5-10. I wrote it with parents and grandparents in mind so the instructions are simple and the experiments only require supplies you probably already have at home!
I gathered our supplies before inviting the kids over. Once they see we’re doing a science experiment they want to dive right in, so I have to make sure that I’m all ready!
I had most of the supplies on hand, but to do this rainbow science experiment we needed a higher concentration of hydrogen peroxide than is typically available at the food/drug store. I made a trip to our local beauty supply shop to buy it, or you can purchase it online here. These are the supplies I gathered:
- Empty spice jars or salt shakers (I had 7 on hand, but you could do more or less, depending on what you have!)
- Baking dish
- 6% Hydrogen peroxide (20 volume clear developer) – Available online or at a beauty supply store
- Food coloring
- Liquid dish soap
- Condiment squeeze bottles
- Dry active yeast
- Lukewarm water
- Measuring spoons and cups
- Wooden skewers
I arranged the empty spice jars in a circle on a large serving plate. Making unicorn toothpaste makes a mess so it’s good to have a dish or baking sheet to catch most of it!
A Note About Safety
I have outlined a few safety precautions in the instructions below. Just be careful and tell your children about the real hazards of using hydrogen peroxide.
However, don’t let the safety warnings keep you from sharing this awesome rainbow science experiment with the kids! My kids are ages 3, 7, and 9 and even the 3-year-old participated in almost every step and was perfectly safe. If you are really worried you could always have the kids wear eye protection and gloves to keep them extra safe!
An adult should definitely handle the hydrogen peroxide since it can cause skin irritation and bleach hair and clothes. Use your own best judgement with the kids you are working with. If they can’t be trusted to keep their hands and mouths away from the hydrogen peroxide, perhaps try a nontoxic rainbow science experiment like this one.
If hydrogen peroxide does come in contact with skin or eyes, flush the area with water immediately. And if a child actually ingests hydrogen peroxide, call Poison Control.
Creating an Exploding Rainbow
Into each spice jar I added 2 tablespoons hydrogen peroxide, a few drops of food coloring, and a small squeeze of liquid dish soap. Since we wanted to make a rainbow we made the jars red, orange, yellow, green, blue, violet, and pink!
The kids did this next step.
They used a funnel to add yeast and water to a couple of condiment squeeze bottles. You want to use a 1:6 ratio of yeast to water. We added 2 tablespoons of yeast and 3/4 cup lukewarm water to each bottle.
The kids used a wooden skewer to mix up the yeast mixture. We waited a few minutes to let the yeast dissolve a little bit.
Next came the REALLY fun part!
The kids took turns squeezing the yeast mixture into each of the colorful salt shakers. One by one they erupted in a brilliant, foamy mess!
If some of the peroxide is left in the spice jar, just add more yeast mixture to it and try stirring with a wooden skewer. The more unicorn toothpaste, the better!
The kids were so amazed! They laughed and clapped in complete fascination as each color erupted into the serving dish and mixed with the rest of the colored foam.
Playing in the Foam
This rainbow foam is too fun not to touch. And it’s totally safe as long as a little bit of caution is used.
As explained below, the actual foam is just soap and water and food coloring. Everything that bubbles out of the spice jars is safe to touch.
HOWEVER. There may be hydrogen peroxide left in the jars. If the kids want to play in the foam just watch carefully and make sure they don’t tip over leftover peroxide from the jars onto their hands.
Another cool thing about this rainbow science experiment is that it is exothermic, meaning it gives off heat. How many times do you get to do a chemical reaction at home that is exothermic?!
The jars will be warm right after the reaction. It’s a wonderful learning experience for the kids to feel the jars after the reaction is complete. I always touch the jars first just to make sure they aren’t too hot for little fingers!
Rainbow Science Experiment
So what’s actually going on with this fascinating rainbow science experiment?
This is a wonderful way to get kids interested in chemistry and science in general!
Hydrogen peroxide is somewhat unstable and easily decomposes into oxygen gas and water all by itself. It usually comes in brown bottles to protect it from being exposed to light, which makes the peroxide decompose even faster.
When yeast is added to the peroxide mixture, it acts as a catalyst. A catalyst makes a chemical reaction happen more quickly.
So when yeast comes into contact with hydrogen peroxide it produces oxygen gas and water very quickly. This happens so quickly that the oxygen bubbles out of the solution vigorously, creating foam and making the mixture overflow!
The foam that is produced looks just like bright rainbow toothpaste that a magical unicorn might use each morning!