TOPIC: Electrochemistry

Demo-032

Gummi Bear Terminator

This demonstration vividly and dramatically illustrates the concept of a strong oxidizer.

MATERIALS

A small package of gummi bears
Ringstand and clamp
One medium sized pyrex test tube
Around 25 g of solid potassium chlorate (KClO
3)
Safety shield and goggles
Fischer burner & striker
Tongs or long forceps

PRESENTATION

This can be used as a "gee whiz" demonstration, or better as an illustration of the basic idea of a strong oxidizer. If used for the latter purpose, it should be presented as part of a discussion of oxidation and reduction. The bottle label states that potassium chlorate is a strong oxidizer, and this demonstration shows what that means.

Fill the test tube to a depth of about one inch with potassium chlorate. Clamp the test tube in place at an approximately 45 angle. Set up the ringstand-clamp-test tube assembly behind a safety shield in front of the class. Connect the burner so that the test tube can be heated easily.

Light the burner and heat the test tube at the bottom until the solid melts (mp is around 350 C). Stand behind the safety shield and carefully drop one gummi bear into the test tube using tongs or forceps. A violent flame-shooting reaction ensues and lasts for about one minute. You class will remember it for years!

DISCUSSION

The gummi bear is mostly sugar, which is easily oxidized by something like molten potassium chlorate. Ideally, a balanced equation would show sucrose (C12H22O11) being converted to carbon dioxide and water while the KClO3 becomes KCl. The actual reaction does not seem to go to total completion since there is usually a little gunky residue left behind.

HAZARDS

Molten KClO3 can cause very severe burns. Think of your skin or the top of the lab bench as another gummi bear. Exercise your best safety technique while presenting this demonstration. It will set a good example for your class. There is also a lot of smoke produced during the oxidation (steam and KCl?), so this experiment should only be done in a room with good ventilation.

 

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