wrote:
ve3... wrote:

Household tip: For some unknown reason, hot water pipes freeze
before cold water pipes.
A trickle of water will prevent pipes from freezing.
Thed Global warming debate will resume in July.

This arctic air has hit the left coast as well.

The deal with the hot water pipe freezing first is due to the lack of
dissolved gasses in the water. That is, the heating process takes the
dissolved gasses out of the water, which in turn makes it easier to
freeze.
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Alas, It ain't so simple. The finest scientific minds of our time have
been unable to come up with a theory that can be proved by experiment.
Current theories include:
- evaporatve cooling
-convection
-dissolved gases
-surrounding environment

The finest scientific minds of our time fool around with experiments
for a while, find that they cannot isolate the variables, and go back
to their lucrative defense dept contracts where things go boom and life
is much simpler.
Aristotle noticed the freezing effect around 350bc but not much was
known about scientific method then and his deduction worked for him.
The modern name for the phenomena is "the Mpemba effect" after an
African student who found that he could freeze hot milk faster than
cold milk. ( to make ice cream)

For those who have way too much time on their hands Google
Why do hot water pipes freeze before cold water pipes?
You will get 1,100,000 hits.

For those with limited time an instructive article from Physics Web
"Does Hot Water Freeze First?"
can be found at:
http://physicsweb.org/articles/world/19/4/4

A scholarly article," Hot water Can Freeze Faster Than Cold?!?", can be
found at:::
http://arxiv.org/ps_cache/physics/pdf/0512/0512262.pdf

This would be a great subject for a science project or even a Phd
thesis.