h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Ok, so I am in the pub with a mate, a plumber, and he tells me hot water will freeze faster than water that is just a few degrees above zero. I say I dont believe it !
So who is correct?

It *can* do...

http://www.scientificamerican.com/article.cfm?id=is-it-true-that-hot-water

In certain experiments it does. If you put a container of cold water into your chest freezer it will just sit there and eventually freeze. If you put a container of hot water into the freezer, it will melt through the frost at the bottom of the freezer, make a really nice heat conducting contact with the base, and the freezer will come on full blast because of the heat. The heat will then be sucked out of the hot liquid through the heat-conducting contact. The result is that the hot water can freeze quicker.

But normally it doesn't.

It would appear that my mate may be correct What he actually said was ' If you throw a bucket of hot water and a bucket cold water on the ground. [ it was below zero outside ] The hot will freeze first ' Humph. Needs an experiment methinks

http://www.bbc.co.uk/news/world-europe-11877471

flash freeze a cup of hot water

what would happen with a cup of cold water????

Presumably it would be a cup of stiff water by then - you'd have to throw the cup with it. Not the same effect at all.

This evening I shall be conducting a LIVE ! experiment at midnight GMT. I shall place 2 shallow plates outside and pour a cup of hot water in one and a cup of cold water in the other. See which one freezes first. Its the coldest night of the year so far so an ideal time to try this out.

OK the plates are out ! 2 plastic plates filled with hot water and cold water respectively.

5 minutes have past. Some condensation on the edge of the hot plate. No sign of freezing yet.

10 minutes. Dipped my finger in each plate. Hot water now just luke warm. Cold water still just cold.

My breath is bated...

15 minutes. Hot water now only a little warmer than the cold.

20 minutes. Little change

25 minutes. little change

30 minutes, Still no sign of freezing. I will give it 10 minutes before looking again.

40 minutes. Both plates now very cold.

Obviously you'll have to do it at least forty times for it to have any statistical validity.

50 minutes. Still not frozen.

1 hour. Both plates very cold when I dipp my finger in.

I havn't managed it once yet.