Re: Mpemba effect" ??

[Savinainen Antti <antti.savinainen@KUOPIO.FI>]

James McKey wrote:

> I've never heard of that name. I have heard the tale about hot water freezing
> faster than cold, but do not see how that's possible for equal starting and
> ending masses of water under equivalent external conditions.

My student did an Extended Essay on the topic few years ago in the
International Baccalaureate program.
She monitored cooling and freezing of the same amounts of water in the same
freezer in different kinds of containers. She used a computer based measurement
of temperature. I didn't believe in the effect before I saw how initially
warmer water actually did froze faster that colder water. The (initially)
colder water spend more time in a super cooled state under 0 degrees of Celsius.
Then the temperature raised to zero and started to drop again after all the
water had frozen. This took place repeatedly for certain kind of containers.
Why this happened remained a mystery.

Regards,

AnttI Savinainen
Kuopio Lyseo High School/IB
Finland