Sunday, April 21, 2013

Does blowing air on a spoon of hot soup cool it?

As explained by Fenyman way back in 1960s, blowing acually speeds up evaporation from the surface of a hot liquid, causing molecules with more energy to leave the liquid and not return back. This decreases overall energy (and heat) in the liquid.

Beware this may reduce the overall soup you drink though :)

Another excerpt from an answer online:
"When you sit down to that steaming bowl of soup, the faster-moving, hotter particles "leap off the surface," evaporating and leaving the slower-moving, cooler particles behind. But these evaporated particles form a little cloud of vapor above your bowl, saturating the air and preventing any more evaporation. When you blow on your soup, you disperse the vapor cloud. This clears the air, so to speak, for more hot particles to evaporate, thus cooling the soup."


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