The “Elephant Toothpaste” demonstration is a classic science experiment known for producing a large column of foam. This popular reaction is a safe way to observe an accelerated chemical process, resulting in a stream of bubbly material that resembles a giant squirt of toothpaste. The sheer volume of the foam that rapidly overflows a container makes this demonstration engaging.
Gathering the Necessary Supplies
The reaction requires two main chemical components and a few pieces of common household equipment. You will need one-half cup of three percent hydrogen peroxide solution, which is commonly found in drugstores, and one tablespoon of dry yeast. You also need three tablespoons of warm water and a squirt of liquid dish soap to capture the gas produced.
For the equipment, an empty plastic bottle, such as a sixteen-ounce soda bottle, works well as the reaction vessel. Its narrow neck forces the foam upward. A small cup is needed to prepare the yeast mixture, and a funnel assists with pouring ingredients. Since the reaction produces a large volume of foam, placing the bottle on a large tray or performing the experiment outdoors is recommended for easy cleanup.
Executing the Experiment
Begin by preparing the yeast mixture. In a small cup, combine one tablespoon of dry yeast with three tablespoons of warm water. Stir the mixture for about thirty seconds until the yeast is fully dissolved. The warm water helps to activate the yeast cells, making the reaction more vigorous when added to the peroxide solution.
Next, carefully pour the half-cup of hydrogen peroxide into the plastic bottle. You can add a few drops of food coloring down the sides of the bottle to create stripes in the final foam. Then, add a squirt of liquid dish soap directly into the peroxide. Gently swirl the bottle to combine the soap and peroxide without creating excessive bubbles prematurely.
With the first two components combined, carefully pour the yeast and water mixture into the bottle. A funnel can be helpful to ensure all the catalyst is quickly added. Immediately step back and observe the reaction as a column of foam rapidly erupts from the bottle opening.
Understanding the Chemical Reaction
The foam eruption results from a rapid chemical reaction called decomposition. Hydrogen peroxide (H2O2) is an unstable compound that naturally breaks down into water (H2O) and oxygen gas (O2) over time. The basic reaction is represented by the formula 2H2O2 → 2H2O + O2.
The dry yeast acts as a catalyst, a substance that speeds up a reaction without being consumed. Yeast contains the enzyme catalase, which is an efficient catalyst for the decomposition of hydrogen peroxide. Catalase lowers the energy required for the peroxide to break apart, causing the reaction to occur almost instantly when the yeast is added.
As the hydrogen peroxide rapidly decomposes, it releases a large volume of oxygen gas. The liquid dish soap traps this oxygen, creating millions of tiny bubbles that push the foamy mass out of the bottle’s opening. Because a small amount of liquid peroxide generates a significant volume of gaseous oxygen, the foam production is extensive.
The reaction is also exothermic, meaning it releases heat energy. The foam will feel warm to the touch due to the energy released during the rapid breakdown of the hydrogen peroxide. The speed of foam formation relates directly to the concentration of peroxide used, with higher concentrations producing a faster eruption.
Essential Safety Precautions and Disposal
Safety is the first consideration, especially when handling the common three percent solution of hydrogen peroxide, which can cause eye irritation. Everyone involved must wear protective eyewear, such as safety goggles, before handling any materials. Conducting the experiment on a protective surface or in a sink will prevent spills from damaging surfaces.
The resulting foam is generally safe to touch once it has cooled. Avoid touching the foam immediately after the eruption. Cleanup is simple because the foam is primarily composed of water, soap, and oxygen. All materials, including the remaining liquid in the bottle, can be safely washed down the sink or drain with plenty of water.