Elephant's toothpaste
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Elephant's toothpaste (or elephant toothpaste) is a popular chemical experiment, involving the rapid formation of a hot foamy substance caused by the quick decomposition of hydrogen peroxide using potassium iodide or yeast and warm water as a catalyst. The speed of the reaction majorly depends on the concentration of hydrogen peroxide.
As the reaction doesn't produce any dangerous byproducts or any flames, and the general perception of foam spreading everywhere is seen as comical by all age groups, this demonstration is a popular experiment for children to perform in school or at parties, or in science fairs.
Contents
How to do the classical experiment
In an open container, a volume of cca. 50 ml of concentrated (>12%) hydrogen peroxide is first mixed with 3 ml liquid soap or dishwashing detergent. A catalyst, which can be either 10 ml potassium iodide solution or baker's yeast, is added to accelerate the decomposition of hydrogen peroxide. The hydrogen peroxide breaks down into oxygen and water, and as it does, it generates a large volume of oxygen. The soapy water, due to its viscosity, traps the oxygen, creating bubbles, and turns into foam, which rapidly spills out of the container, often in a spectacular fashion. Since the resulting foam is white, a few drops of food coloring can be added before the catalyst to dramatize the effect.
If the concentration of the hydrogen peroxide used in the experiment is 50%, then the decomposition of the mixture will be violent, almost instant. This version of the experiment is sometimes called Devil's toothpaste.
Other catalysts can be used, like potassium permanganate.
Mechanism
Hydrogen peroxide decomposes into water and oxygen gas, which is in the form of foam, but under normal circumstances, the reaction is too slow to be easily perceived.
- H2O2 → H2O + ½ O2
The iodide ion from potassium iodide acts as a catalyst and speeds up the reaction, by changing the mechanism through which the reaction occurs, while remaining chemically unchanged in the reaction process:
- H2O2 + I- → H2O + IO-
- H2O2 + IO- → H2O + O2 + I-
Safety and handling
Hydrogen peroxide is caustic to bare skin, and contact will lead to bleaching of skin, which is serious if it involves conc. peroxide.
The heat generated from the decomposition of H2O2 can reach temperatures of 75 °C, enough to cause serious burns.
Video demonstrations
- ELEPHANT’S TOOTHPASTE: An impressive experiment you can try at home
- Elephant Toothpaste (Chemistry)
- "Elephant Toothpaste" with Potassium permanganate and Hydrogen peroxide
