Robt R Pries
Tue, 13 Nov 2007 12:58:22 PST
Several people have mentioned that water gives off
heat as it freezes. If I remember my physics
accurately it is quite a lot of heat. 1 calorie is the
amount of heat it takes to raise one cc of liquid
water 1 degree F. It takes 80 calories to change from
ice to water and vice versa. In other words the amount
of heat it would take to raise the temperature 80
degrees is what is absorbed by melting ice or given
off by freezing water. Just imagine the tremendous
number of calories that are being absorbed presently
by the melting ice caps at the North Pole. Once that
ice is gone imagine how hot it could get without
something out there to absorb the excess.  
 Bob Pries, zone 5-6 having a rather warm November
day. And we our normal hard frost is about 20 days
--- Jonathan Knisely <> wrote:

> I tend to favor Jim McKenney's explanation.
> What I have observed, and what I have read, is that
> there may be a difference
> among plants in their ability to tolerate
> subfreezing temperatures based upon
> the presence of 'antifreeze-like' soluble compounds
> that can prevent the
> nucleation of ice crystals in plant cells. 
> Differences between kale and
> lettuce might be partially explained by something
> like this.  I don't believe
> that the cells would 'want' to deplete themselves of
> water--what would they do
> when the temperature got higher at midday?
> I wonder whether the anecdotal benefit of dousing
> frosted plants (that are not
> frozen) with water is because of the significant
> heat capacity of water as it
> undergoes a phase change from liquid to solid.  The
> splash of water would
> prevent the nucleation of intracellular ice--all
> that 'outside' water would
> need to freeze before the intracellular water (with
> those special solutes)
> would freeze.
> Jonathan Knisely
> Coastal Connecticut, USDA 6a
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