Is the popular belief that 100° steam is more injurious to the skin than boiling water just a wives tale?
There's more energy in the steam. To raise the temperature of one gram of water from 37'C (temperature of skin) to 100'C (the boiling point) requires 63 calories (one calorie per degree). To convert that gram of water to steam requires another 540 calories. So the energy in the steam is 9-fold greater than the energy in the same weight of water at the boiling point. This energy (as heat) is released when the steam condenses to water and the water cools to the temperature of skin. Steam will be substantially more injurious.
David Kessel, Ph.D., Professor, Wayne State University, Detroit
Steam burns do have to potential to cause more damage than scalding. The reason has to do with the latent heat of vaporization. This is the amount of heat energy necessary to change the phase or state of matter from liquid to gas. This energy is absorbed by the liquid, but does not change the temperature. Conversely, when a gas condenses, it must release this latent heat and become a liquid before it can cool below its boiling temperature. The latent heat of vaporization for water at sea level is about 2250 J/g, as compared to the specific heat of water of about 4 J/g''C. All that extra heat has to go somewhere, mostly to the surrounding air. If, however, you place your hand into a jet of steam, much of that heat will be absorbed by your skin - very unhealthy. And what's worse, as the steam condenses onto your skin, it will still be at 100'C!
Grant Coble, B.S., Physics Teacher, Hollywood High, Hollywood California.
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