Re: cooling water

[Hugh Logan <hlogan@ix.netcom.com>]

LUDWIK KOWALSKI wrote:
> The issue of "hot water freezing faster" can be resolved by an experiment.
> Put a glass of 50 C water into a freezer and measure the time it takes
> Put a glass of 30 C water into a freezer and measure the time it takes
> to reach the temperature of -1 C, for example. Then do the same with
> 5 C wate, under identical conditions. A CBL thermistor could be used to
> monitor the temperature from outside. My prediction is that it will take
> longer when the initial temperature is higher. But I am ready to rething
> to rethink this if the experiments show I am wrong.

Jearl Walker states that it is common knowledge in cold regions such as 
Canada or Iceland that hot water left outside will freeze faster than
cool water. (_The Flying Circus of Physics with Answers_ by Jearl
Walker, Wiley, 1977, p.55, Item 3.40. Walker gives several references). 
My father, who told me about this at an early age, was born in Canada.
According to Walker this phenomenon was observed by Francis
Bacon (1561-1626), who, according to the science educators of the
1940's, if not the present day ones, was often regarded as the inventor
of the scientific method (for whatever that is worth). 

Walker suggests "putting warm and cool water in various containers
either outside on a freezing night or in your freezer. If in any of your
tests the warm water freezes first, then you'll have to explain why."

I think your proposed test represents just one possible set of
conditions under which the experiment can be performed. Very likely your
prediction is correct. But what if the air above the container is set in
motion by a fan? I think the outdoor test is more likely to show that
hot water freezes first, but you will have to wait until next winter to
try that.

Hugh Logan