| MadSci Network: Physics |
First, I must admit that I am not in any way an expert on this subject!! If you have read any of the articles referenced in the hot link of this answer then you already know more than I do! However, I want to add some comments based on my 30 years of experience as a scientist.
The discussion here (which is at the hotlink given in the answer I gave above!) indicates five factors that may have something to do with the effect, but several others are mentioned without specifically calling them out as "factors". Among these others are: 1) surface roughness of the container, 2) size, shape, and thickness of the container, 3) starting temperatures, and 4) the "freezing" temperature (the ambient temperature in which the containers are placed). Other factors that I can think of, which are not specifically mentioned in this article, are 5) purity of the water, 6) cleanliness of the containers, 7) air movement around the containers, 8) relative humidity of the ambient air, and 9) the characteristics of the surface on which the containers sit. I'm sure there are many other factors!!!!
With all these factors, it is probably impossible to totally isolate each one in any experiment that can be devised, and so an accurate model would be hard to make. But, if I were going to actually make a model (on my computer, probably!) using the most important factors my guess is that the model would be 80% to 90% accurate. That's just a guess! My model would use container size and thickness, ambient (final) temperature, starting temperatures, amount of water, vapor pressure (which is a function of temperature and is the major factor in evaporation), a simple model of convection, ambient relative humidity, and the movement of air around the containers.
After having said all that, I have not actually constructed a computer model. So I can not specifically answer your question about at what temperatures the cold water would actually freeze first. Keep in mind, though, that since there is a lot of discussion about the effect then the effect itself is probably difficult to reproduce. For one thing, it would be difficult to know exactly when all the water has actually frozen!! But don't let me discourage you from trying it!! Another thing you might try, if you are at all practiced at writing computer programs (or using spreadsheets), is to make a model and see the outcome of various starting parameters. I would be extremely interested in knowing anything you discover, and if the results are significant we would actually post them on our site!
Happy freezing!!
John Link, MadSci Physicist
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