Tuesday, February 20, 2007

Can hot water freeze before cold water?

Joel's camelbac, what a work of insulation.

Check out that insulated tube on Joel's camelbac.


Hi Cheryl and Pierre,

At the pre-race meeting you mentioned that we should not fill our water containers with hot water because hot water freezes before cold water. Anyone who is around a hockey arena knows this to be true because flooding is always done with hot water for this very reason.

Many of the racers were sceptical when you said this and some even voiced their opinion and said that you were wrong. Here is a good website link which explains the phenomenon which is called the Mpemba Effect.

http://math.ucr.edu/home/baez/physics/General/hot_water.html

Personally, I've experimented with using both cold and hot water in my camelbac and found that tube takes longer to freeze when cold water is used.

Thought that you might be interested.

Bill

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Thanks, Bill. Interesting but hard to follow. I think we saw something about it once on a TV science show. It is easier just to put two dog dishes out on the porch and watch (as any of us who lived in Northern MN or Canada already know).

Did you ever try throwing boiling water into the air when it is well below zero outside? It explodes/disappears in a poof of gas or crystals. Cold water doesn’t do this, so I always thought it must have something to do with instability of boiling water or evaporation or something like that.
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As the article mentions, it must be a complex interaction of a variety of conditions that come into play. The amount and depth of the water and how much surface is exposed to air, etc. must have something to do with it. I grew up on the shore of Lake Superior and when it got below zero the Lake would steam like it was boiling. It also froze over on the surface most every year for a few weeks so we could ice skate and would make eery creaking noises as the ice cracked and piled up on shore.

There are some cool photos of the Lake ice in the Duluth paper today.

http://www.duluthnewstribune.com/photography/includes/gallery.cfm?id=105

regards,
Cheryl

1 Comments:

Blogger AM said...

Interesting. Evaporative cooling of the hot water would help explain the dog dish or hockey rink examples, but water does not evaporate out of a reservoir. My experience has been that luke-warm water in a reservoir takes longer to freeze up than cold water... Guess I need to experiment some more.

1:53 PM  

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