You can google "Elephant's toothpaste" to get other recipes for this one. We use it to demonstrate rates of reaction. Get 100ml of 30% H2O2 and warm it in a microwave (presuming you store your peroxide in the fridge, it will be cold, so try 2 mins in microwave), and pour into a large measuring cylinder -250mL or 500mL. Get another 100ml of COLD H2O2 and pour it into a second measuring cylinder. Add a generous squeeze of dishwashing detergent to each. Stand both cylinders in a trough. Have a teacher at your side, and measure out one spatula full each (ie 2 spatulae) of KI (Potassium Iodide). Say "One two three!" or something similar and add the KI to the cylinders. STAND BACK.
The hot H2O2 will react violently, with a column of bubbles shooting up into the air. The cold H2O2 will react slowly, but eventually produce more bubbles, as the O2 is released more slowly, and therefore has time to form bubbles in the soap mix. DON'T TOUCH the foam, and DON'T let the kids touch it. The iodine generated can invade your fingernails and hurt for days, speaking entirely from personal experience. However, you can observe the heat generated by the reaction, in the form of steam emanating from the bubbles, from both the hot and the cold H2O2. The KI is a cleaner catalyst then MnO2, but beware of the iodine.
Good Luck. Kristin
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