the following info drawn from wikipedia may provide a field for further input- no doubt there can be other explanations but the effect seems to be real;
<https://en.wikipedia.org/wiki/Mpemba_effect>
<The effect is named after
Tanzanian Erasto Mpemba. He described in 1963 in Form 3 of Magamba Secondary School,
Tanganyika, when freezing ice cream mix that was hot in cookery classes and noticing that it froze before the cold mix.
He later became a student at Mkwawa Secondary (formerly High) School in
Iringa. The headmaster invited Dr. Denis G. Osborne from the University College in
Dar Es Salaam to give a lecture on physics.
After the lecture, Erasto Mpemba asked him the question "If you take two similar containers with equal volumes of water, one at 35 °C (95 °F) and the other at 100 °C (212 °F), and put them into a freezer, the one that started at 100 °C (212 °F) freezes first. Why?",
only to be ridiculed by his classmates and teacher. After initial consternation, Osborne experimented on the issue back at his workplace and confirmed Mpemba's finding.
They published the results together in 1969, while Mpemba was studying at the
College of African Wildlife Management.
[8]
A reviewer for
Physics World writes, "Even if the Mpemba effect is real — if hot water can sometimes freeze more quickly than cold — it is not clear whether the explanation would be trivial or illuminating." He pointed out that investigations of the phenomenon need to control a large number of initial parameters (including type and initial temperature of the water, dissolved gas and other impurities, and size, shape and material of the container, and temperature of the refrigerator) and need to settle on a particular method of establishing the time of freezing, all of which might affect the presence or absence of the Mpemba effect. The required vast multidimensional array of experiments might explain why the effect is not yet understood.
[1]
New Scientist recommends starting the experiment with containers at 35 °C (95 °F) and 5 °C (41 °F) to maximize the effect.
[16]
In a related study, it was found that freezer temperature also affects the probability of observing the Mpemba phenomena as well as container temperature. For a liquid bath freezer, a temperature range of −3 °C (27 °F) to −8 °C (18 °F) was recommended.
[14]
In 2012, the
Royal Society of Chemistry held a competition calling for papers offering explanations to the Mpemba effect.
[17] More than 22,000 people entered and Erasto Mpemba himself announced Nikola Bregović as the winner, suggesting that convection and supercooling were the reasons for the effect.
[18]>