Elephant's Toothpaste

1. The first step is to put on your safety glasses.
2. Measure 20 mL of the 30% hydrogen peroxide into the graduated cylinder. It's best to place the cylinder in a large tray to make the clean-up as easy as possible.
3. Add a squirt (that's a technical term meaning about 5 mL) of dish soap to the graduated cylinder containing the 30% hydrogen peroxide.
4. Add a few drops of food coloring to spice things up.
5. The last step is to add 5 mL of the 2M sodium iodide solution (2M refers to the molarity of the solution). The reaction takes place quickly, so it's important to stand back.
6. You'll notice that the foam has a brown tint. This is due to the presence of free iodine produced by the extreme oxidizing power of the 30% hydrogen peroxide.

Concentration Variations

Steve recently used the Elephant's Toothpaste experiment to help answer the question, "Why is Science Important?"  Steve and some special guests used four different concentrations of hydrogen peroxide to explore the scientific method and the process by which theories can be tested.

Because it is often hard for anyone but a chemistry teacher to obtain 30% hydrogen peroxide, we wanted to test the effectiveness of other concentrations of peroxide.  3% hydrogen peroxide is the household concentration that would typically be used for cuts and scrapes.  But, hair stylists can purchase peroxide that is anywhere from 6% to 12%.

1. To make the four different solutions in the video, Steve used regular 30% hydrogen peroxide and diluted it by 1/2.  He then diluted the 15% solution by half and the 7.5% solution by half.  However, you can use various concentrations of peroxide available at drugstores, beauty supply stores, and to chemists.
2. The most important part of the experiment is that everything stays the same except for the concentrations of peroxide.  Each cylinder should have 30 mL of hydrogen peroxide, 5 mL of dish soap, and 5 mL of 2M sodium iodide.
3. Collect your data by measuring the height of your eruption on the graduated cylinder.

How does it work?

You might remember Mom treating your scraped knee or a cut with hydrogen peroxide. H₂O₂ is the scientific name for hydrogen peroxide which is made up of two hydrogen atoms and two oxygen atoms. H₂O₂ looks like ordinary water (H₂O), but the addition of that extra oxygen atom turns the molecule into an extremely powerful oxidizer. The hydrogen peroxide found at the grocery store is a low grade 3% solution which is safe to touch but powerful enough to kill bacteria, viruses, and fungi on surfaces.

The hydrogen peroxide used in this demonstration is ten times stronger than the over-the-counter hydrogen peroxide you can find at the store. Low grade hydrogen peroxide (3%) will not produce the massive amount of foam seen in the Elephant's Toothpaste demonstration. The secret ingredient is actually sodium iodide which acts as a catalyst - something that speeds up the decomposition of hydrogen peroxide. When hydrogen peroxide (H₂O₂) decomposes, it breaks down to form water (H₂O) and oxygen (O₂). The soap bubbles that erupt from the cylinder are actually filled with oxygen. As the reaction takes place, you'll also see steam rising from the erupting foam. This shows that the reaction is exothermic (gives off heat).

Hydrogen peroxide (30% strength) will act as an oxidizing agent with practically any substance. This substance is severely corrosive to the skin, eyes, and respiratory tract. Sodium iodide is slightly toxic by ingestion. Given these safety precautions, it's best to leave this one to the experts. Just befriend a chemistry teacher and ask her to perform the famous Elephant's Toothpaste experiment.

Additional Info

Check out the Halloween version with oozing pumpkins!