This makes an excellent science demonstration for high school students when performed by a trained adult professional. Potassium chlorate (available through most chemical suppliers, such as Sigma-Aldrich – www.sigmaaldrich.com) is a white solid and perfectly safe to handle under normal conditions. Potassium chlorate is oxygen-rich, meaning it acts as a good “oxidizing agent”, causing materials mixed with the potassium chlorate to become “oxidized”. A striking example of this can be found in the infamous “Exploding Gummi Bear” demonstration. Don’t worry – the gummi bear doesn’t actually explode. However, it is rapidly and rather spectacularly consumed.
A test tube (wide enough to accommodate the gummi bear) is loaded with about an inch of potassium chlorate crystals. This test tube is clamped in tongs and then gently heated over a bunsen burner flame, keeping the open end pointed towards the back of a safety fume hood. Because potassium chlorate melts at approx. 350 degrees Celsius, by steadily heating it over the hottest part of the burner flame all the solid will melt, and you will soon have a cloudy liquid happily bubbling away in the tube. Pick up a gummi bear with a separate set of tongs (in reality, any candy made of sugar will work, but gummi bears are traditional) and drop it into the tube.
Instantly, a vigorous, even violent chemical reaction takes place. The oxygen given off by the heated chlorate rapidly attacks the sugars in the candy, transforming them into carbon dioxide gas and water. The resultant energy is given off as light – a *lot* of light as the case turns out. An ex-Army friend of mine compared it to a magnesium flare. The only other product is harmless potassium chloride salt.
It’s difficult to put into words just how vigorous this reaction is. Here is a link to a Youtube video showing this exact reaction in progress:
After the reaction is over, the contents (when cool – you don’t want to crack the test tube) can be safely washed down the drain with running water. Don’t attempt to reuse the contents of the tube for a second try. Potassium chlorate is extremely cheap and this makes a fantastic demonstration for kids of all ages, although extreme caution must be adhered to in that only an adult should handle the actual experimentation.
Have fun!
