Our guide on how to make elephant toothpaste outlines a version that is safe for children, avoiding the burn risk of the classic recipe.
You can conduct this fun experiment with hydrogen peroxide from the drugstore and a few ingredients that you are bound to find in the household. A colored foam snake winds around the PET bottle almost like toothpaste from an oversized tube.
The well-known experiment shows another important ability that not only yeast cells but also our cells have: the ability to protect themselves from oxidizing agents. And since it creates a lot of gas, you can use this ability for this fun experiment.
The classic experiment uses 30% hydrogen peroxide, which is not safe for children. However, the recipe below using 6% or 3% hydrogen peroxide, which is much safer and still a lot of fun.
- PET bottle (½ liter) or similar tall vessel with a small opening
- Hydrogen peroxide 6% or 3%, approx. litre, from the drugstore.
- Dish soap (1/4 cuo)
- Dry yeast (packet)
- a glass with some warm water
- suitable surface, e.g. a baking sheet
- optional: food coloring (a few drops)
When handling hydrogen peroxide, it is recommended that you wear safety glasses, gloves, and a lab coat (or a paint coat).
Hydrogen peroxide is a strong oxidizing agent (depending on its concentration), ie it bleaches textiles and burns the skin. Contact with clothes, skin and especially with the eyes must therefore be avoided at all costs! The reactivity / danger increases with the concentration, which is why we only carry out the experiment with a 6% or 3% solution. In an emergency, immediately rinse the affected area with water.
How to do it:
- Put on protective goggles, a laboratory coat and gloves
- Pour 1/2 cup hydrogen peroxide solution, 1/4 cup dishwashing soap, and a few drops of food coloring into the bottle. Swish the bottle around to mix the ingredients. Set the bottle in a sink or outdoors or some other place where you won’t mind getting wet foam everywhere.
- In a separate container, mix a packet of active yeast with a little warm water. Give the yeast about five minutes to activate before proceeding to the next step.
- When you are ready to do the demo, Quickly pour the yeast solution into the PET bottle and quickly withdraw your hand, the reaction starts immediately upon the addition of the yeast.
- Watch as the mixture immediately begins to bubble and foam violently. The foam oozes out of the vessel opening like a strand of toothpaste and pours out / snakes around on the outside of the baking sheet.
The “toothpaste” and leftovers in the reaction container can be disposed of down the drain with plenty of water. You can store the remaining hydrogen peroxide solution in the tightly closing original container in a dark cupboard and use it later for further experiments.
The chemistry of elephant toothpaste
A solution of H 2 O 2 (hydrogen peroxide) and then yeast is added to an aqueous solution with washing-up liquid. The following happens:
Hydrogen peroxide breaks down into water and oxygen. Due to the large amount of gaseous oxygen, the volume in the piston or cylinder increases suddenly and the mass is pushed out of the vessel. The detergent creates large amounts of foam. The yeast acts as a catalyst.
H 2 O 2 + I – → IO – + H 2 O
H 2 O 2 + IO – → I – + H 2 O + O 2
So the overall reaction is: 2 H 2 O 2 ⟶ 2 H 2 O + O 2
By the way: even if “toothpaste” suggests something else: elephant toothpaste is of course not allowed to be swallowed or put in the mouth. Not even as an elephant.
However, if hydrogen peroxide comes into contact with other substances, it oxidizes most of them. This is especially true for the components of living beings. Therefore, that is why you should wear protective glasses and clothing during this experiment!
Protection against oxidation by clean-up enzymes
When the cells of oxygen-breathing organisms (humans, animals, yeasts, …) obtain energy from oxygen, however, H 2 O 2 can arise in them as an undesirable by-product (as well as the well-thought-out reaction pathways, they are far from running correctly). So that this hydrogen peroxide does not oxidize wildly, the cells have a clean-up command that removes any H 2 O 2 that may arise from errors as quickly as possible.
These are enzymes called catalase. These are proteins that accelerate the natural decomposition of hydrogen peroxide in water and oxygen many times over – by making the reaction much easier.
A biocatalyst makes the reaction easier
Because reactions are easier when less energy is needed to start them. A substance that can accelerate a reaction (without reacting itself) by reducing the activation energy required to start the reaction is called a catalyst.
In a car, the catalytic converter is a metal surface on which toxic exhaust gases react to form less toxic substances. In living beings, the catalysts are called enzymes. Enzymes are proteins that facilitate and thus accelerate reactions. The catalases are among the fastest enzymes of all: A single catalase molecule is estimated to convert up to 10 million H 2 O 2 molecules per second! As a result, the rate at which hydrogen peroxide is broken down with catalase depends practically only on how much H 2 O 2 the enzyme can “grab” in a given time.
Gas development thanks to catalase
This makes the catalase ideally suited for immediately eliminating hydrogen peroxide that occurs due to errors in other reaction processes – or for releasing large amounts of oxygen gas from hydrogen peroxide that penetrates from the outside in a very short time.
If we expose our yeast to (relatively) large amounts of H 2 O 2 by mixing with hydrogen peroxide solution , these small molecules storm the yeast cells and are immediately converted into water and oxygen gas. If the cells burst or their outer walls are broken and oxidized, the catalase comes into direct contact with the hydrogen peroxide solution and the gas is created even faster.
Now gaseous substances need many times more space than liquid substances from the same particles, so that the oxygen gas expands very quickly. However, since our mixture contains soap, the resulting portions of oxygen are enclosed in tiny soap bubbles: Foam is created.
And this foam, wet from soapy water and yeast cell residues, oozes out of the vessel as an “elephant toothpaste” snake.
The “elephant toothpaste” consists of foam made of soap and oxygen, which is created by “overfeeding” the oxidation protection enzymes of yeast cells with hydrogen peroxide.
Human cells also have catalases, which accelerate the breakdown of hydrogen peroxide in the same way: When hydrogen peroxide gets into our skin, small oxygen bubbles develop in the tissue, which we can see as the white injuries.
Important: The body’s protective enzymes are designed to remove oxidizing agents that are created when there are errors in the cell’s own processes. Other oxidizing agents and bleaching agents, especially dangerous chlorine compounds sold under the abbreviation “MMS” as “miracle cures” are not included! The human body has no protective measures of its own against such substances!