Elephant Toothpaste Materials
•50-100 ml of 30% hydrogen peroxide (H2O2) solution
•saturated potassium iodide (KI) solution
•liquid dishwashing detergent
•500 mL graduated cylinder
Wear disposable gloves and safety glasses. Oxygen is evolved in this reaction, so do not perform this demonstration near an open flame. Also, the reaction is exothermic, producing a fair amount of heat, so do not lean over the graduated cylinder when the solutions are mixed. Leave your gloves on following the demonstration to aid with cleanup. The solution and foam may be rinsed down the drain with water.
1.Put on gloves and safety glasses. The iodine from the reaction may stain surfaces so you might want to cover your workspace with an open garbage bag or a layer of paper towels.
2.Pour ~50 mL of 30% hydrogen peroxide solution into the graduated cylinder.
3.Squirt in a little dishwashing detergent and swirl it around.
4.You can place 5-10 drops of food coloring along the wall of the cylinder to make the foam resemble striped toothpaste.
5.Add ~10 mL of potassium iodide solution. Do not lean over the cylinder when you do this, as the reaction is very vigorous and you may get splashed or possibly burned by steam.
6.You may touch a glowing splint to the foam to to relight it, indicating the presence of oxygen.
Elephant Toothpaste Chemistry
The overall equation for this reaction is:
2 H2O2(aq) --> 2 H2O(l) + O2(g)
However, the decomposition of the hydrogen peroxide into water and oxygen is catalzyed by the iodide ion.
H2O2(aq) + I-(aq) --> OI-(aq) + H2O(l)
H2O2(aq) + OI-(aq) --> I-(aq) + H2O(l) + O2(g)
The dishwashing detergent captures the oxygen as bubbles. Food coloring can color the foam. The heat from this exothermic reaction is such that the foam may steam. If the demonstration is performed using a plastic bottle, you can expect slight distortion of the bottle from the heat.