Genie in the Bottle

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As noted in previous posts, we use chemical magic to get the attention of the audience. However, we are not magicians in the strict sense. Magicians do not share their secrets. We use magic to get the attention of the audience then we reveal how the trick was done. Our aim is to emphasize that the magic is in the chemistry not the sleight-of-hand.

This approach is best illustrated in the classic demonstration: Genie in the Bottle. In this demonstration, the demonstrator points to an opaque flask (generally a stoppered, taped Florence flask) and tells the audience that there is a Genie locked up inside the flask. In order to release it, the stopper is removed. In a few seconds steam shoots from the flask as if the Genie is released.

In our version of this demonstration, we make no pretext about magic and show the audience how the demonstration is set up. We tell the audience that the flask contains 30% hydrogen peroxide. Separately, we have a coffee filter containing potassium iodide with a piece of string tied to it. The filter is placed inside the flask without touching the liquid. The string is held in place with the stopper (In the “trick” version, the excess string is cut off.). We remove the stopper allowing the KI to contact the liquid causing the reaction to occur.

We explain to the audience that the KI catalyzes the decomposition of the hydrogen peroxide generating heat and steam. We have just introduced a new word, “catalyze”, to many members of the audience. We explain to them how important catalysts are in chemistry. For example, converting a barrel of oil to dress shirts requires extensive use of catalysts.

WOW! What a transition – from divulging a simple, but eye-catching chemical magic trick to explaining catalysis!

Note of caution: 30% hydrogen peroxide is a strong oxidant and causes servere burns to the skin. An alternative version of this demo using 3% hydrogen peroxide is cited in the pdf document associated wih this video.

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