From: utzoo!decvax!harpo!floyd!rjs
Newsgroups: net.physics
Title: A different ice question (summary of answers)
Article-I.D.: floyd.1440
Posted: Fri Apr 15 11:15:46 1983
Received: Sat Apr 16 06:39:48 1983


I received a number of letters regarding my inquiry as to whether or
not warm water freezes faster than cold water.  Many of them refered
to a Scientific American Amature Scientist article on the subject, so
I looked back through my old issues and found it in the September 1977
issue.  This was the special issue on microelectronics which may explain
why so many people knew about it.  This article does make the claim
that hot water freezes faster than cold.  It also says that the explaination
is still the subject of controversy.  The possible reasons offered are
better circulation of hot water, hot water contains less dissolved gas, and
that hot water loses a substantial amount of mass to evaporation, so you
are actually freezing less water.

The author then goes on to present the results of his experiments, which
show a definite drop off in freezing time after a certain temperature
which depends on the conditions (amount of water, size of container, type
of freezer, covered or uncovered container).  In any case, looking at
his data, it still seems that cold tap water (usually < 20 deg. C.) than
water that is warmer (but still water i.e. < 100 deg. C.).  The turnover
point on his data occurs in the 60-80 deg. C. range.

My conclusion is that you are still better off using cold water as you
don't have to pay to heat the water then cool off that heat.  Also,
you don't want to run the risk of getting rid of all the dissolved
gasses or the ice won't float (just kidding).

Thanks to all who answered.

	Robert Snyder
	floyd!rjs