Elephant Toothpaste

Concept

A catalyst is used to start a chemical reaction. The catalyst aids to a reaction and speeds up the reaction process.

Materials

• • 2 grams of cobalt chloride
  • 2 g. sodium carbonate
  • 30 mL distilled water
  • 5 mL dish detergent
  • 15 mL of 30% hydrogen peroxide
  • Small beaker
  • Larger graduated cylinder
  • Bucket or pan to catch overflow
  • Plastic gloves
  • Safety goggles

Procedure:

• Prepare Steps 1, 2, and 3 right before the demo
• See safety precautions at the end before starting!!

1. Mix cobalt chloride and sodium carbonate in a small beaker.
2. Add the distilled water, stir to mix thoroughly, and then add the dish detergent to the beaker.
3. Stir until the solids dissolve somewhat.
4. Put the graduated cylinder into the pan or bucket and then pour the solution into the large graduated cylinder.
5. Making sure gloves and safety goggles are on; quickly pour the hydrogen peroxide into the cylinder and STAND BACK.
6. Foam will form, rise up the cylinder, and overflow into the pan or bucket. (Heat is also a product. DO NOT TOUCH).

Explanation & Reaction

A catalyst speeds up the reaction of an experiment. The cobalt chloride speeds up the chemical reaction because it speeds up the decomposition of hydrogen peroxide to form oxygen gas. The detergent captures the oxygen in bubbles, which is what we see as foam. A reaction that gives off heat, like this one does, is exothermic. I'm using hydrogen peroxide, like you might use at home, except this kind is much stronger. The hydrogen peroxide you might get from the drug store is only 3%, while the hydrogen peroxide I'm using is 30%. That is why I'm wearing gloves and safety glasses.

The point of this demo is to decompose the hydrogen peroxide (H₂O₂) as rapidly as possible, which generates gaseous oxygen (O₂). When combined with simple dishwashing soap, you get rapid formation of bubbles.

2 H₂O₂ (aq) --> 2 H₂O (l) + O₂ (g)  + energy

This decomposition reaction can be catalyzed with iodide ions by introducing KI (aq).

H₂O₂ (aq) + I^- (aq) --> OI^-(aq) + H₂O(l)

H₂O₂ (aq) + OI^- (aq) --> I^- (aq) + H₂O (l) + O₂ (g)

Another difference in this experiment is the difference between the symbols for hydrogen peroxide verses water. Water has the symbol H₂O, while hydrogen peroxide has the symbol H₂O₂. This difference is seems slight, but it is a huge difference when doing this experiment.

Safety

• Always wear plastic gloves when working with 30 % hydrogen peroxide. Also be extremely careful when working with this substance. It will burn your skin if you touch it.
• Always wear safety goggles when doing this experiment. The foam shoots very high out of the cylinder and could go towards you face.
• After the experiment, wait a considerable amount of time before handling. The cylinder does become hot and is dangerous to hold.

Waste Disposal

• The foam can be disposed of down the sink. And the empty beakers, as well, can be cleaned safely in the sink.
• Do not eat anything here. It may look tasty, but control yourself.

References

1. Stone, C. H. J. Chem. Ed. 1944, 21, 300.

Outside Links

• http://www.using-hydrogen-peroxide.c...oothpaste.html
• http://chemistry.about.com/od/chemis...phanttooth.htm

Contributors

• Charles Ophardt, Professor Emeritus, Elmhurst College; Virtual Chembook

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