Not that I'm doubting anyone's Physics knowledge, but a very similar question was posed on an exam I took in college...

Freezing air temperature outside, two buckets of the same amount of distilled H2O in each. One at room temp, one boiling. All other factors considered equal, which freezes first?

The answer given was similar to TartanBill's explanation of the hot water losing some mass by excited particles evaporating, therefore less mass freezes faster.

I'll talk to my pal today and see if he's got a better explanation for why he uses hot water.

[This message has been edited by kpmcd (edited September 14, 1999).]