Since I spend my days at work sticking my hand in liquid nitrogen (-219C, -321F) I found the Leidenfrost Effect, the effect that protects my hands from extreme temperature, pretty cool. Here is a demonstration with liquid nitrogen. The video below is the mythbusters jamming their hands into molten lead unharmed because of the effect. Not really busting a myth because it is already a scientific fact but still cool. Starts at 1:55.
Update-The Leidenfrost effect also allows you to pre-heat a skillet and add ingredients without sticking to the pan. Good kitchen tip.
5 comments:
This is not to be confused with the "lederhosen effect," which miraculously protects men wearing German leather breeches from any amorous advances from the opposite sex.
In addition to creating a bit of insulating water vapor, we learned in high school chemistry that, since it takes 540 calories for a gram of water to be converted to gas, putting your wet hand into molten lead is a good way to cool off.
Not good at recognizing jokes online but the heat transfer is from the steam to the hand not vice versa. So it would be like cooling off in a sauna, not really possible.
You're right about not being good at recognizing on-line jokes. (That's a joke.)
But even though it was a joke, the scientific theory is sound, if misplaced. During the Leidenfrost effect water will immediately be converted to water vapor. To do that it needs 540 calories of heat per gram of water. It needs the heat just for the conversion without raising its own temperature. Where does it get the heat? From your hand! ...Well, there is some molten lead nearby also.
So, of course you're right in saying cooling off in a vat of molten lead or a sauna is not a good idea, but I would be interested if anyone has ever done an experiment to see if your hand actually cools an infinitesimal amount for an infinitesimal amount of time, before it heats up (and burns off to a stump after the Leiderfrost effect is past).
I don't even recognize my own on-line jokes.
For example, I heard this recently: The job of a college dean is like that of a cemetery caretaker. You're over a lot of people, but good luck trying to get them to do anything.
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