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Author Topic: What freezes first, hot or cold water - part 1  (Read 15811 times)

sharkeyandgeorge

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What freezes first, hot or cold water - part 1
« on: 08/03/2005 10:57:53 »
heres a experiment for all you scientists out there take boiling water and room temp water and put them in the freezer at the same time you should find the boiling water freezes first anyone know why that is my guesses are

oxegen in the water slows the freezeing process
or
it takes time for the radiation of heat to start but boiling you kick start this process and though it has further to go it gets there faster

i dont know if either is close to the right reason

ps in the line of the whats the largest organ on the body question whats the freezing temp of water? its probably not what you think

Interesting, no the other thing... tedious.
The philosopher Bender


 

Offline chris

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Re: What freezes first, hot or cold water - part 1
« Reply #1 on: 08/03/2005 18:12:58 »
Sorry mate, but this is a MYTH.

Although the boiling water loses heat more rapidly than the cold water, because the thermal gradient is much greater, the cold water will still reach freezing temperature first, and form an ice cube.

The only reason that you might see this effect is if the two samples of water are different i.e. are different volumes, or of different compositions. For instance if the cold water has not been boiled first and then allowed to cool - this is important because boiling removes temporary hardness (bicarbonates) which could otherwise lower the melting point.

Chris

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Offline gsmollin

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Re: What freezes first, hot or cold water - part 1
« Reply #2 on: 08/03/2005 18:42:35 »
The largest organ in the body is the skin. That one's easy. The freezing temperature of water is a fuzzy target, depending upon how you cool it. I assume the water sample is pure, distilled water. The water usually freezes somewhat below the usual 0 C number because of supercooling. Likewise, it boils somewhat above 100 C because of superheating. The Celsius scale is not calibrated by freezing water, but rather the triple point.

That bit about hot boiled water freezing before room temp water, has been making the rounds for years. You can probably google it and finds more hits than you care to chase down. I did do such a search a couple of years ago and found a lot of "scientists" who claim to have done "scientific" experiments to prove it is true. However, I never saw the kind of data I need to persuade me. To wit: Details about the water chemistry, its preparation, the experimental apparatus, the procedure, and not even a data set of the water temperatures during the experiment. Just a claim that the boiled, "hot" water froze first. I don't even know what their definition of "frozen" was. An ice skin? Frozen solid? <0 C?

Anyway, I lost interest since I cannot support or refute a claim that is not backed up by a REPEATABLE experiment.
 

sharkeyandgeorge

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Re: What freezes first, hot or cold water - part 1
« Reply #3 on: 08/03/2005 20:52:58 »
fair enough about the boiling water but im only repeating what ive heard from several sources sorry if im wrong but i thought the sources were reliable
 

Offline chris

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Re: What freezes first, hot or cold water - part 1
« Reply #4 on: 09/03/2005 10:30:47 »
That's alright - it's what we're here for, and it stimulated some discussion, which is the point of this forum.

Chris

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Offline gsmollin

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Re: What freezes first, hot or cold water - part 1
« Reply #5 on: 09/03/2005 10:52:34 »
You don't have to be sorry. There was no flame in my response, although perhaps frustration was evident. I really did spend some time trying to find out the details of the claims, and how these experiments were carried out, but there was a dearth of actual detail. Lots of anecdotes. If you have some "sources" for this I would be glad to look again, but you may find, when you look critically, that the claims are un-substantiated.
 

sharkeyandgeorge

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Re: What freezes first, hot or cold water - part 1
« Reply #6 on: 09/03/2005 21:20:34 »
i have one tv source open university rough science and my high school physics teacher who didnt show us it but told us about it and asked us why(we never came up with an answer) ive also heard it many time anecdotally though of course that is not reliable. ive decided to try it myself and will be doing it first thing in the morning when i can watch

Interesting, no the other thing... tedious.
The philosopher Bender
 

Offline DrPhil

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Re: What freezes first, hot or cold water - part 1
« Reply #7 on: 09/03/2005 23:26:02 »
Here's an answer by some guys that Scientific American thought were at least credible enough to ask.
sciam.com ASK THE EXPERTS
 

Offline gsmollin

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Re: What freezes first, hot or cold water - part 1
« Reply #8 on: 10/03/2005 16:31:13 »
That link amply illustrates the points in my previous post. It is full of anecdotal information, but no actual data. The authors suggest people try this at home without telling them how to do it, and what to measure. Then they go on about all the variables that cause people to get different answers. So different home investigators will get the two different possible answers: 1) hot water freezes before cold water, and 2) hot water freezes after cold water. Confusion reigns.
 

Offline DrPhil

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Re: What freezes first, hot or cold water - part 1
« Reply #9 on: 10/03/2005 20:30:37 »
I agree.

Seems that all the folks who have the qualifications and proper lab equipment to conduct the experiment have never bothered to actually do it. They can explain in great detail what they think should happen but have nothing to back it up. The only people that have ever tried the experiment are the ones staring at their ice cube trays in the kitchen fridge.
 

sharkeyandgeorge

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Re: What freezes first, hot or cold water - part 1
« Reply #10 on: 11/03/2005 20:48:40 »
Well i went and tried it and IT WORKED!

In an indusrial freezer room(-20C) at work I put two full ice cube trays one of hot water just of the boil 92.3C and another out the tap 15.4c on a wire trolly in the middle of the room after 20mins the boiling water tray had frozen solid and the tap water was still slushy .4C Idont know if this satisfies you but it DOES seem to work
 

Offline chimera

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Re: What freezes first, hot or cold water - part 1
« Reply #11 on: 11/03/2005 21:45:31 »
So, would it maybe have to do with the fact that temperature is a kind of information, and that 'spreads faster' in a hotter medium? Like learning a trick, sort of?
 

Offline gsmollin

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Re: What freezes first, hot or cold water - part 1
« Reply #12 on: 12/03/2005 00:29:25 »
What's the water hardness of the tap water. What was the water hardness of the boiled water? What was the mass of the water in the trays at the start of the chilling, and at the "end"? How long was the chilling? Do you have a temperature vs time dataset? Was the cold water straight from the tap, or was it boiled first, then cooled to 15.4 C.
 

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Re: What freezes first, hot or cold water - part 1
« Reply #12 on: 12/03/2005 00:29:25 »

 

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