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Old 10-26-2000, 09:55 PM
Collidingworlds Collidingworlds is offline
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Hi Cecil,

I just read your article questioning which freezes faster, hot water or cold water. I'd like to enlighten your readers. Water changes temperature at a constant level providing the heat or cooling source remains constant. Most
freezer's remain at the same temperature so we'll submit the cooling source is constant. The rate of freeze is relative to the volume of water (how much water needs to be cooled). Given that, logic concludes that if water
in ice trays cools at 5 degrees per minute (for example), then the cooler water will reach freezing temperature faster than the hot water. Duh?

The inquiry from Ellen about an article in Scientific American brings in a new variable. Heat contains energy. The more heat, the more energy. When extremely hot water, containing lots of energy, is cooled quickly, the energy disipation in the water accelerates the cooling process. The energy is visible in the form of evaporation (OK, it's the steam you see, not the evaporation). This was originally discovered by ancient Egyptians who would
soak cloth in water and hang it by a window (which were alreadys open since there was no plate glass to shut.) The arid climate of the desert and the wind blowing in the window would cause the cloths to evaporate quickly, so
much so that the energy disipation would cause the cloth to freeze over. Surprisingly, the room would be about 30 degrees cooler than the outside.

I think I'll go work on a new theory: How fast do you have to drink a can of beer before the warmth of your fingers warms the beer. Sounds like a challenge!
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Old 10-26-2000, 10:41 PM
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bare bare is offline
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Ahh, Lad...So much to learn and so little time. Keep looking.
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Old 10-27-2000, 11:01 AM
Arnold Winkelried Arnold Winkelried is offline
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don't forget the link to the online column

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Which freezes faster, hot water or cold water?

The column (including Slug Signorino's illustration) can also be found on pages 98-101 of Cecil Adams’ book «More of the Straight Dope».

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Old 10-27-2000, 11:03 AM
Arnold Winkelried Arnold Winkelried is offline
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Quote:
Originally posted by Collidingworlds
This was originally discovered by ancient Egyptians who would
soak cloth in water and hang it by a window (which were alreadys open since there was no plate glass to shut.) The arid climate of the desert and the wind blowing in the window would cause the cloths to evaporate quickly, so
much so that the energy disipation would cause the cloth to freeze over.
The cloth would freeze over even if the temperature of the room in which the cloth was hanging was above 0°C? I am skeptical.
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Old 10-27-2000, 11:17 AM
jab1 jab1 is offline
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Old 10-27-2000, 01:37 PM
Joe_Cool Joe_Cool is offline
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Quote:
Originally posted by Arnold Winkelried
The cloth would freeze over even if the temperature of the room in which the cloth was hanging was above 0°C? I am skeptical.
I'm not. I live in New Jersey now. In the summertime if you get wet it doesn't cool you off at all. It just means you're still hot, only now you're wet, too. But when I used to live in Albuquerque, NM, wet clothes could get really cold, to the point of extreme discomfort if there was a good breeze. And that's outside in 90 degree weather. It's probably even more noticeable in someplace like Arizona or the California deserts.

I don't know what part of the country you live in, but in a desert climate, water evaporates FAST, and evaporation is what drives refrigeration & air conditioning. To be honest I never thought it would freeze, but then Albuquerque is nowhere near as dry as Egypt. I could imagine it happening if the conditions were right (a really dry day with a good stiff wind).
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Old 10-27-2000, 01:51 PM
Joe_Cool Joe_Cool is offline
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Quote:
Originally posted by Joe_Cool
...in 90 degree weather...
Um, that's 90°F, of course.
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Old 10-27-2000, 03:05 PM
ZenBeam ZenBeam is offline
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Quote:
Water changes temperature at a constant level providing the heat or cooling source remains constant
No, the amount of heat transfer is proportional to the difference in temperature. This means the rate of change of temperature of the water will slow as the water gets closer to the freezer temperature.

As far as the cloth freezing, I suppose that's possible at night when the temperature isn't as much above freezing as during the day. I've had frost form on my car when parked outside, when the overnight low was above freezing.
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