If an elephant used toothpaste, this is probably what it'd look like! Working with an adult, kids can learn about chemical reactions by watching this heat-producing mixture bubble and overflow for up to half an hour.
WARNING: This experiment uses chemicals that can irritate skin and damage clothes, so make sure to use safety goggles, lab apron, and nitrile gloves. Avoid touching or getting the chemicals on skin or clothing. And don't get too close, as heat and steam can be dangerous.
DON'T FORGET YOUR SAFETY EQUIPMENT: safety goggles, lab apron, nitrile gloves
WHAT'S GOING ON
Hydrogen peroxide normally decomposes (breaks down into separate elements), and combining it with detergent and yeast (a catalyst) speeds up the process.
As the oxygen emanates from the reaction, it creates bubbles. The detergent speeds up the foaming. The reaction is "exothermic," meaning it produces heat as well as steam.