The elephant toothpaste chemistry demonstration is a dramatic demo which produces copious amounts of steaming foam that sort of looks like the toothpaste an elephant might use. Here's how to set up this demonstration and a look at the reaction behind it.
Elephant Toothpaste Materials
- 50-100 ml of 30% hydrogen peroxide (H2O2) solution
- saturated potassium iodide (KI) solution
- liquid dishwashing detergent
- food coloring
- 500 mL graduated cylinder
- splint (optional)
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.
- 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.
- Pour ~50 mL of 30% hydrogen peroxide solution into the graduated cylinder.
- Squirt in a little dishwashing detergent and swirl it around.
- You can place 5-10 drops of food coloring along the wall of the cylinder to make the foam resemble striped toothpaste.
- 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.
- You may touch a glowing splint to the foam to to relight it, indicating the presence of oxygen.
Variations of the Elephant Toothpaste Demonstration
- You can add 5 grams of starch to the hydrogen peroxide. When the potassium iodide is added, the resulting foam will have light and dark patches from the reaction of some of the starch to form triiodide.
- You can use yeast instead of potassium iodide. Foam is produced more slowly, but you can add a fluorescent dye to this reaction to produce elephant toothpaste that will glow very brightly under a black light.
- You can color the demonstration and make it into an Elephant Toothpaste Christmas Tree for the holidays.
- There is also a kid-friendly version of the elephant toothpaste demo that is safe for hands.
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.