[Joe L. Ogan (OP)]

Will hot water ever freeze faster than cold water.  If it does, why does it freeze faster than cold water?  Thanks for comments.  Joe L. Ogan

[RD]

Try searching for "Mpemba".

[Joe L. Ogan (OP)]

Yes, I am familiar with this URL but there appears to be some uncertainty about "Why" hot water freezes faster than cold water.  Do you know?  Thanks for comments.  Joe L. Ogan

[lightarrow]

Hot water can freeze faster than cold water in a lot of ways:
1. Put hot water inside a freezer, while put cold water inside a fridge   []
2. Allow hot water to vaporize so that a little amount of water will be really refrigerated, it will freeze faster than a large amount of cold water   []
...
...
explore the many possibilities.

Hot water cannot freeze faster than cold water!

What's happened to schools/colleges in the last years?  []

[Joe L. Ogan (OP)]

The fact that hot water will freeze faster than cold water is an established fact.  The reason "WHY" has never been established.  Thanks for comments.  Joe L. Ogan

[lightarrow]

An established fact by who? Where are scientific papers about that? Where is written in physics books? Which are the universities or the physics professors at university who claim this?

[Joe L. Ogan (OP)]

Look at Mpemba physics effect.  Thanks for comments.  Joe L. Ogan

[tommya300]

.
Wow Whoo wee. Sorry Lightarrow I have jumped before looking to many times and needed people to slap the back of my head and tell me more then once, thanks you all, and I hope I can help here!

 I have seen and did an experiment using a glacial substance, relating to this, but it was a long time and is foggy to remember. I do remember graphing delta Temp vs. time and the surprising thing was the hotter water lost heat faster then the cooler water over time. I know that is not what was asked here.

So I searched through allot of things, including the suggested, Mpemba physics effect, which I just learned here, and would of never knew it if it were not for this Site and all of you people.
Thank You Joe and RD...
I read that it is easier to explain that water melts at 32 F than it is to say it freezes at 32 F.

Special conditions are the key.
Changing liquid water to a solid ice form, I read that ice crystallization starts at 40 degrees F.
 I also read that super cooling water to below 32 F it can still be a liquid and then flash freeze to a solid.
Conditions:
This Question needs conditions to place any definite answer to it.

I read that there is "no one Mechanism" can cover all the conditions and give an absolute result.
Mpemba physics effect is the closest and the most recognized condition that the science communities can see yet!

I drink my sodas without ice but at temperatures as close to 32 F as I can or even from a bottle
I think, in my younger day, reading a beer label, Michelob beer label suggests to serve the brew at 42 degrees; they may be observing the frosty phenomena? If I opened a can of beer that was cold enough a slushy ice would form in a glass as I poured it out. Oh yea that happened when I put salt in the ice of my cooler and then stuck the cans of beverage and waited an hour or so.


Does anyone still stick a hot poker in their Yard or Mug of beer? Hot beer?

 Stumbling again I found a U-Cal has a write-up that can help here.

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

[tommya300]

An exhibit of conditional freezing, ice solid forming before your very eyes

[hotdigittydogger]

I did the experiment... cold water froze first.  Try it yourself.  Why would anyone think hot water freezes faster?  Let's give it a quick thought.  If you start with water that is 1 degree above freezing, and another that is 30 degrees above freezing, is it not common sense that the water that only needs to drop 1 degree will do so faster than that which needs to drop 30?

[Joe L. Ogan (OP)]

Well, Aristotle, Descartes and many others have performed the experiment and their hot water froze first.  Later experiments have verified the fact.  Please look at Mpemba.  Thanks for comments.  Joe L. Ogan

[lightarrow]

To the school-didn't-teach-us-anything fan: if water at 40°F takes 1 minute to go down to 32°F and freezes, water at 41°F will need x time to go down to 40°F and then 1 minute to freeze. Do you mean that x is a negative value?

[Joe L. Ogan (OP)]

I am not trying to prove the phenomenon.  It has already been proven!  I am trying to find out "WHY" it works that way.  Thanks for comments.  Joe L. Ogan

[tommya300]

I am not trying to prove the phenomenon.  It has already been proven!  I am trying to find out "WHY" it works that way.  Thanks for comments.  Joe L. Ogan

"JLO'n'Mpemba" physics effect, a catchy label for the future physics books discribing the phenomenon and the reason why.

[tommya300]

Producing a miniature weather pattern:
Steamy energetic water, in  a container, producing water vapors, is placed in a freezer.
The surface of the water in the container is cooling as the vapors escape.
But not all water vapors are lost, some condense and circulate above in a cycle to attempt to gain a lattice crystal structure, precipitates, dropping to the surface and transfers the exchange of heat.
When the water surface reaches its highest density the lattice crystallization begins at the condensed vapor level  and begins to displace the warm water below it. As this happens water begins to freeze at the surface first.
It is the vapors of the hot water creating an additional heat sink.
Note it is slushy not solid ice.
The other room temperature water does not have the abundance of energetic water vapors to do this extra heat sink exchange

[JP]

I am not trying to prove the phenomenon.  It has already been proven!  I am trying to find out "WHY" it works that way.  Thanks for comments.  Joe L. Ogan

"Proven" wouldn't be the phrase I'd use.  It seems that in certain cases, you can get hotter water to freeze faster than colder water, though this isn't the case all the time.  Clearly, if average temperature is the only factor that matters (i.e. if the hot and cold water always have an even distribution of temperature, particulates, etc. throughout), then Lightarrow's argument holds: hot water first has to take time to cool to the cold water temperature, and then it takes the same time as the cold water did to freeze, so it can't possibly win the race to freeze first.  The problem is that apparently temperature isn't the only factor that matters, but that makes coming up with a good model difficult, since modeling water's exact behavior is complicated. 

The explanation that makes the most sense to me is that water isn't even in temperature throughout: hot water tends to rise and cold water to sink.  This can cause cooling to proceed at a faster rate than expected due to convection currents.  When the hot water reaches the cold water's starting temperature, it might have more hot water at the top and cold water at the bottom due to these currents than the cold water did when it started.  This will cause it to take less time to go from "cold" to freezing than the cold water does. 

But modeling and experimenting to test this are both very complicated, so the effect isn't well understood.  Usually people just throw out the fact that "hot water freezes faster than cold water," which isn't true.  It can do so under certain conditions, but it's not a general rule.

Edit: I see that the link tommya300 pretty much says the same thing I do, but in better detail.

[Joe L. Ogan (OP)]

Producing a miniature weather pattern:
Steamy energetic water, in  a container, producing water vapors, is placed in a freezer.
The surface of the water in the container is cooling as the vapors escape.
But not all water vapors are lost, some condense and circulate above in a cycle to attempt to gain a lattice crystal structure, precipitates, dropping to the surface and transfers the exchange of heat.
When the water surface reaches its highest density the lattice crystallization begins at the condensed vapor level  and begins to displace the warm water below it. As this happens water begins to freeze at the surface first.
It is the vapors of the hot water creating an additional heat sink.
Note it is slushy not solid ice.
The other room temperature water does not have the abundance of energetic water vapors to do this extra heat sink exchange. 

This is the most logical explanation that I have seen in regard to the phenomenon.  Have you performed experiments to substantiate your conclusions?  If so, I believe you should write it up and submit it for consideration.  This is not a new subject.  I remember reading about it many years ago.  Thanks for comments.  Joe L. Ogan

[Mootle]

You might find this http://www.physorg.com/news188801988.html of interest.

You would be forgiven for thinking that water is pretty simple, when in fact water is really tricky stuff, it literally has hundreds on known properties. Some of these properties are more readily measured than others. This makes it is very difficult to be sure that you are comparing apples for apples, which goes someway to explain why this dilemma has vexed folk for so long.

However, if you start with two identical samples of water and expose them to identical conditions, and then apply heat to one of the samples, it would be the cooler of the two samples which goes on to freeze first, every time!

[Joe L. Ogan (OP)]

Yes, I am aware that it does not happen every time.  In fact, one may well say that it requires special arrangements for it to occur at all.  But the fact that it does occur is very intriguing to me and always has been.  When I first heard it, I did not believe it at all but the evidence is too much for it not to happen.  Thanks for comments.  Joe L. Ogan

[tommya300]

Producing a miniature weather pattern:
Steamy energetic water, in a container, producing water vapors, is placed in a freezer.
The surface of the water in the container is cooling as the vapors escape.
But not all water vapors are lost, some condense and circulate above in a cycle to attempt to gain a lattice crystal structure, precipitates, dropping to the surface and transfers the exchange of heat.
When the water surface reaches its highest density the lattice crystallization begins at the condensed vapor level and begins to displace the warm water below it. As this happens water begins to freeze at the surface first.
It is the vapors of the hot water creating an additional heat sink.
Note it is slushy not solid ice.
The other room temperature water does not have the abundance of energetic water vapors to do this extra heat sink exchange. 

This is the most logical explanation that I have seen in regard to the phenomenon.  Have you performed experiments to substantiate your conclusions?  If so, I believe you should write it up and submit it for consideration.  This is not a new subject.  I remember reading about it many years ago.  Thanks for comments.  Joe L. Ogan

Joe I do not have access to lab equipment anymore.
I have not the finances to get my own equipment.
The thermal measuring equipment can not make contact with any parts of the model.

IR camera is needed to focus into the center of the vapor front.
Like trying to take a picture of the inside of a cloud.
Hi tech equipment something like miniature Halographic Doppler radar imaging. If there is such a thing.
I think the solution to the question should be viewed from meteorological aspect, combined with thermal sciences of the properties of water as each important stage of the process, can be observed.
After your question on why it works I said the catchy name for the phenomenon JLO'n 
So I searched the net and read about water as it interacts in the air. I stumbled on a few edu articles    

"JLO'n'Mpemba" physics effect, a catchy label for the future physics books describing the phenomenon and the reason why.
.
If this were to become a solution, hope the proceeds go to help the children, tomorrows future.