Misplaced Electrochemistry Our home has two smoke detectors, both powered by 9-Valkaline batteries. When their output falls below a certain level, they activate a noise device, and replacements are purchased. On one such recent occasion, I placed the "dead" battery in a pocket so I would rememher my mission at the hardware store (absent-minded professors do indeed exist!). After checking to compare the battery type numbers, I returned the old one to the side pocket of my pants. After paying for the new battery, I added the change to the same pocket. As I was driving home, a copper penny apparently made contact with the anode and cathode of the "dead" hattery. I suddenly felt a burning sensation against my upper thigh. This unexpected event occurred in the midst of traffic and caused intense excitement! Fortunately it did not cause an accident. I could imagine the local headlines andmy reputation in ruins. The "dead" battery was not quite a t its minimum in free energy (recall that AG = -nFE). A sufficient voltage remained to remind me that W = EIt, or the product of voltage X current (amps) X time (seconds) gives joules. Perhaps you may recall Murphy's famous Heat Theorem: too many joules in the wrong place a t the wrong time can cause one hell of a problem. There is a moral to this story: "dead" batteries and loose change should not mingle, or someone may have to retire your shingle.
Allen A. Denlo Unlverslty of Wisconsin-Esu Claire Eau Claire. WI 54701
1020
Journal of Chemical Education
