There are few science demonstrations that excite children more than chemical reactions. Just a brief search of all the Mentos / Coke videos on YouTube provide more than ample evidence to support my claim!
To tap into this joy and curiosity around the Halloween season, I’ve been wrapping up my “Pumpkin Science” show for second graders with a classic Elephant Toothpaste demonstration I’ve renamed “Pumpkin Puke!” When the potassium iodide mixed in a dish soap and water solution come into contact with concentrated hydrogen peroxide, the molecules react and kick off an exothermic reaction (you can see the steam as heat is released and water evaporated!) The hydrogen peroxide breaks down to form additional water while releasing oxygen gas, which becomes caught in the soapy solution, forming bubbles and quickly expanding beyond the volume of their container.
Enjoy safely using gloves and protective eyewear. Have a happy halloween!