Experiment

This is what happens when chemistry teachers get tired of doing the same old Elephant's Toothpaste demo over and over again. Wally Keesecker from Heritage High School shared this demo on television with Steve Spangler during a Halloween Science episode. Here are Wally's directions…

1. Fill a small beaker with 30 mL of hydrogen peroxide (30%) and add a squirt of liquid dish soap. Add a few drops of food color for effect.
2. Place the beaker inside a carved pumpkin and secure it so that the beaker doesn't accidentally tip over.
3. Fill a plastic syringe with 10 mL of the catalyst – a 2M solution of sodium iodide. Attach a small piece (approximately 30 cm) of plastic tubing onto the end of the syringe.
4. Poke a small hole through the backside of the pumpkin just large enough to feed the plastic tubing through.
5. Feed the tubing through the hole and place the end of the tubing into the beaker (make sure that there's not even a drop of the catalyst on the end of the tubing or you'll accidentally trigger the reaction).
6. Don't forget to replace the top of the pumpkin! When you're ready to go, gently squeeze the syringe, pushing the catalyst into the beaker with the hydrogen peroxide and soap. If everything goes according to plan, the pumpkin will ooze with expanding foam.

As always, be careful not to touch the foam with your bare hands. Always wear safety glasses and protective gloves… and remember to cover your demo surface with a sheet of plastic for easy clean-up.

How Does It Work?

You might remember Mom treating your scraped knee or a cut with a 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 foam that erupts from the cylinder is actually soap bubbles filled with oxygen gas.

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.