Hot water freezes faster than cold water?

[hillzagold]

http://math.ucr.edu/home/baez/physics/General/hot_water.html
http://everything2.com/index.pl?node_id=656818
http://en.wikipedia.org/wiki/Mpemba_effect

Discuss.

[Fenix]

I dunno about that, but cold water boils faster.

;)

[paragon]

I thought everyone knew this.

[hillzagold]

I thought nobody knew this. The average man wouldn't believe this.

[Fallrider]

I never really thought about it, but if you put your tongue on a frozen poll it freezes almost instantly. So it does make sense.

[paragon]

And if you put an ice cube on a freezing pole it melts :O

[Skylark]

Hot water will freeze faster than cold water, but only if impurities exist in the water itself. Of course, impurities are generally a given, so the theory is quite sound, but if we're talking pure water, then hot water will in fact freeze slower than cold water.

One of those weird little facts I learned in high school. Kinda like how distilled water will never boil.

[hillzagold]

One problem with this explanation is that many experiments pre-boiled both the initially hot and initially cold water, precisely to eliminate the effect of dissolved gasses, and yet they still saw the effect [5,13]. Two somewhat unsystematic experiments found that varying the gas content of the water made no substantial difference to the Mpemba effect [9,12].
are you sure of that?

[josh]

hmm. never thought of this before. nice one.

[DontHate]

interesting... i never knew this.

[coalescence]

I never really thought about it, but if you put your tongue on a frozen poll it freezes almost instantly. So it does make sense.


I don't see what that has to do with the topic. Thats just the freezing and the fact saliva cools very fast when its exposed to fresh air.
The thing you could better aks yourself is;
Will a cold tongue freeze slower to a poll than a warm tongue?

[hillzagold]

hell yes

a cold tongue will have had some of it's saliva freeze already, but a warm tongue will be covered in it. this is asuming that you mean 'covered in frost' when you say cold

[Warsaw]

Yeah i cant believe there are so many things i never knew about something as simple as water and now i have to pee....

[MarineCorp]

Interesting, i never learned about this before nice find :good: