Elephant Toothpaste Chemistry Demonstration

The dramatic elephant toothpaste chemistry demonstration produces copious amounts of steaming foam that looks like the kind of toothpaste an elephant might use to brush his tusks. To see how to set up this demo and learn the science of the reaction behind it, read on. Elephant Toothpaste Materials The chemical reaction in this demonstration is between the hydrogen peroxide and a solution of potassium iodide and dishwashing detergent that captures the gases to make bubbles. 50-100 ml of 30% hydrogen peroxide (H2O2) solution (Note: This hydrogen peroxide solution is much more concentrated than the kind youd generally purchase at a pharmacy. You can find 30% peroxide at a beauty supply store, science supply store, or online.)Saturated potassium iodide (KI) solutionLiquid dishwashing detergentFood coloring500 mL graduated cylinderSplint (optional) Safety For this demonstration, its advisable to wear disposable gloves and safety glasses. Since oxygen is involved in this reaction, 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. Elephant Toothpaste Procedure 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 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.Theres also a kid-friendly version of the elephant toothpaste demo thats safe for little hands. 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 catalyzed 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 a slight distortion of the bottle due to the heat. Elephant Toothpaste Experiment Fast Facts Materials: 30% hydrogen peroxide, concentrated potassium iodide solution or a packet of dry yeast, liquid dishwashing detergent, food coloring (optional), starch (optional)Concepts Illustrated: This demonstration illustrates exothermic reactions, chemical changes, catalysis, and decomposition reactions. Usually, the demo is performed less to discuss the chemistry and more to raise interest in chemistry. It is one of the easiest and most dramatic chemistry demonstrations available.Time Required: The reaction is instantaneous. Set-up can be completed in under half an hour.Level: The demonstration is suitable for all age groups, particularly to raise interest in science and chemical reactions. Because the hydrogen peroxide is a strong oxidizer and because heat is generated by the reaction, the demonstration is best performed by an experienced science teacher. It should not be performed by unsupervised children.