Don't bet a pint on this

[ChrisR]

You want some ice quickly.
You have two mugs of water, one warmer than the other.
But only space in the freezer for one mug.

Would you be better to take the warmer water or the cooler?

 

[EliteHeat]

Cor, if I had a pint for everytime someone asked me about the Mpemba effect then I'd have almost have a pint by now.

P.S. It doesn't seem to work when trying to freeze a hot pipe though does it? - cah! physics!

 

[chrishutt]

In most circumstances, colder water would freeze more quickly for obvious reasons. However it is possible to contrive circumstances where warmer water will freeze more quickly (the Mpemba effect - Google this for more details).

I suspect the best strategy might be to put the colder water in the freezer, but first to put some water on the base of the mug to form a better contact with the cold shelf underneath.

 

[ChrisR]

Odd thing is, it doesn't have to be "contrived". It's common. Better convection, therefore coolth transfer, would be my guess as to the main reason.