On Friday, December 5, 2014 4:52:30 PM UTC-5, micky wrote:
On Fri, 5 Dec 2014 05:53:54 -0800 (PST), TimR
wrote:

On Thursday, December 4, 2014 5:12:54 PM UTC-5, micky wrote:
Take the same care with the hot water pipes you do with the cold. It
turns out hot water pipes can freeze sooner than cold water.


I'm familiar with the Mpemba effect, but didn't know it applied to water pipes. Is there evidence for this?

I think I first heard about it on this ng, wrt water pipes. It wasn't
called by any special name then, so to search for the post one would
have to look for freeze or frozen and hold and cold water and pipe, and
it's probably not worth it. I don't remember for sure if the poster was
telling about what he heard or what he had happen at his own home.

I think it's for real. Wikip gives a bunch or reports for this as far
back as Aristotle and including Francis Bacon and Descartes.


Go repeat the shot glass experiment in my previous post. Let us know
the results.


Wikip things the definition of freezing is important.

Maybe. But so far, I haven't seen an agreed on reference experiment
that reliably shows the effect, that many other credible scientists
have been able to then reproduce and agree, verify that it is happening.
Have you?


Agreement on what
is freezing would be important to duplicate these earlier reports, but
it's not important otherwise. Whatever definition is used for hot water
should be used for cold water, Duh.

Agree, that's why I said maybe, above.



Of course if you leave the cold water running and don't run the hot
water until it freezes, the hot water will freeze first. No one is
talking about that. It certainly seems possible to me that when water
is heated it changes physically so that it then cools more quickly.

But what is hard to fathom is how such small changes could overcome
the fact that the hot water still has so much more energy to lose before
it can freeze. If we were talking about some special conditions, where
one is just a few degrees different, I could see that happening. But the
M effect is alleged to occur with a big temp difference, eg like that
between hot tap water and cold being talked about here.



That's a lot less strange than 1000 other things that happen on earth.
I've never been close enough to a bunch of water molecules to see what
happens.


But modern science pretty much has been to that level and way beyond.
The problem here, AFAIK, is that the proponents of the M effect don't
have a simple reference experiment, reproduceable, verifiable by the
scientific community to show that the effect is real. Certainly not
with water at 140F and 70F, in a beaker or similar, placed into a
0F, controlled freezing environment, that's for sure.