Messy Science: Erupting Foam

Recently all three of my kids have become fans of the Amazon Prime show "Annedroids," which follows roughly 12 year old Anne, two friends, and a trio of adorable androids as they use science to solve a variety of problems. My own credulity is stretched to the breaking point as I try to pretend it is possible to for a pre-teen to create self-directed, learning, and emotional robots out of parts found at a junk yard, but the kids love it and it seems harmless enough.
Anyway, in one of the early episodes Anne and her androids created what she simply termed a "chemical reaction" from common household ingredients: hydrogen peroxide, dish soap, and yeast. The results, which were probably just a wee bit exaggerated for TV, were spectacular, with pink foam exploding all over poor Shania, not once but twice in the course of the episode.
Needless to say, my kids have been clamoring to try it ever since.

Here's what we did

Gather materials

* Hydrogen Peroxide (the 3% solution in the brown bottle you can get from the pharmacy section at any store for under $1 is fine)
* Dish soap
* Packet of dry active yeast
* Warm water
* Large container (pitcher or clean 2 liter soda bottle)
* Small cup

Experiment! 

The episode did not give any measurements, and the characters performed the experiment a couple of times with different amounts anyway.
So we just went for it!
1. We took everything outside and placed it on a tray
2. I proofed the yeast by adding about 3-4 Tbsp of warm tap water to the yeast in a small measuring cup. Lucy stirred this mixture with a stick
3. I added a few drops of food coloring to the pitcher
4. Grace poured in about 3/4 of a bottle of H2O2 (aka Hydrogen Peroxide)

5. I squirted in perhaps 1 Tbsp of blue dish soap
6. James poured the yeast mixture into the H2O2 & soap mixture.

Results 

As expected, the results were not Quite as spectacular as on TV, but they were satisfying nevertheless. At first I was afraid all we were going to get was a couple of inches of bubbles in the pitcher (which was only about 1/3 full of H2O2.) But over the space of about a minute, the foam grew and grew and grew until it overflowed the pitcher and even my shallow tray. (Yes, I was very glad we'd done it on the porch!)

The kids were pretty excited, especially 3 year old Lucy who had a blast flinging the (surprisingly warm) foam about for quite some time. In fact, we all had fun playing with the stuff for maybe 15 minutes before I made James drag out the hose and spray off the mess.

So, Why?! 

According to sciencebob.com, the reaction occurs when the yeast steals oxygen from the hydrogen peroxide. The reaction occurs so quickly that millions of tiny oxygen-containing bubbles are formed. The reaction is exothermic, meaning that it generates heat (releases energy), but not so much in our experience that you're in any danger of getting burned. The resultant mixture is just soapy water, so it's safe to play with and wash down the drain.
I'm going to have to admit, though, I couldn't interest even James in the "why" of the whole thing: they just wanted to see things foam up!