RSC Offers $1,600 for theory.
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Topic: RSC Offers $1,600 for theory.
Posted By: Horizons
Subject: RSC Offers $1,600 for theory.
Date Posted: June 27 2012 at 15:23
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http://www.rsc.org/AboutUs/News/PressReleases/2012/mpemba-effect-water-ice-hot.asp" rel="nofollow - http://www.rsc.org/AboutUs/News/PressReleases/2012/mpemba-effect-water-ice-hot.asp
Thought this was interesting.. Why does hot water freeze faster than cold water? ------------- Crushed like a rose in the riverflow. |
Replies:
Posted By: rushfan4
Date Posted: June 27 2012 at 15:25
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It is all about the Zambonis. ------------- 
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Posted By: Equality 7-2521
Date Posted: June 27 2012 at 16:24
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Before someone comes in saying they tried it and this doesn't work, or someone just get confused in general. This does not occur for all temperatures of water. The idea isn't that hotter water always freezes faster; it is that under certain conditions hotter water can freeze faster. So don't go boiling water to make some quick ice cubes. ------------- "One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. " |
Posted By: The Doctor
Date Posted: June 27 2012 at 16:50
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Warmer water has less density than cooler water, and therefore the same volume of water would contain less mass of the warmer water than the cooler water. Depending on if the density differential is enough to compensate for the differential in temperature, it seems that warmer water would sometimes freeze faster than cooler water. Not a proof of any sort, but that's my theory.
------------- I can understand your anger at me, but what did the horse I rode in on ever do to you? |
Posted By: Equality 7-2521
Date Posted: June 29 2012 at 17:46
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If that were the case, you would expect the effect to manifest itself in a wider range of initial conditions. Higher temperature water also freezes differently than the cooler temperature. This difference cannot be so much explained by density conditions. I'm not calling you wrong because I have no way of knowing that. However, it was an initial assumption of mine, but after reflecting on it for a bit I've abandoned it. I know too little about subatomic structures and chemistry to even theorize much. I would think that the heated water's molecular composition differs significantly by removing bound gases allowing the freezing process to occur more rapidly on the molecular level. It'd be cool if somebody figured this out. Some of the geniuses of the last millennium have been stumped by this, but we have a lot more accumulated knowledge to apply towards this. I think our ability to run controlled experiments should make this able to be done. ------------- "One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. " |
Posted By: The T
Date Posted: June 29 2012 at 18:07
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It clearly has to be related each substance's midichlorian count. ------------- 
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Posted By: Aaron Carter
Date Posted: June 29 2012 at 23:05
this doesn't work, or someone just get confused in general. This does not occur for all temperatures of water. The idea isn't that hotter water always freezes faster; it is that under certain conditions hotter water can freeze faster.
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Posted By: Equality 7-2521
Date Posted: June 29 2012 at 23:36
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^That's a weird bot. ------------- "One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. " |
Posted By: The Doctor
Date Posted: June 29 2012 at 23:49
I was thinking that was some kind of spam bot myself. One of his posts was really weird, an exact copy of part of someone else's post without any quote. But would he freeze faster than a real PA poster? That's the question we should all be asking. ------------- I can understand your anger at me, but what did the horse I rode in on ever do to you? |
Equality 7-2521 wrote:Posted By: Dean
Date Posted: June 30 2012 at 04:56
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[taking Pat's idea of bound gasses]
Ice made from heated water is clearer than ice made from cold water. This is also a known effect, partly due to the reduced http://en.wikipedia.org/wiki/Water_aeration" rel="nofollow - aeration of the water caused by boiling and partly by the way inpurities settle-out in the freezing water. It would be a good guess (and without accurate measurement of the aeration and impurity levels and appropriate controlled experiment it is only a guess) that the speed of freezing could be related to the amount of oxygen in the water at the moment of freezing. This could explain why it doesn't work for all temperatures and conditions. Also, pure water is an insulator, ice is also an insulator, poor conductors of electricity are also poor conductors of heat, how the water freezes determines how quickly an insulating layer of ice is formed that could slow down the freezing process, therefore another guess is that colder water freezes around the outside first, creating an insulating barrier slowing the freezing of the water inside the cube - you can see this effect in ice produced in bar ice-machines they put in your Cuba Libre (they are hollow) - it could be that hotter water (the molecules being more active) freezes more evenly and does not create this insulating barrier of ice.
/edit: the last part also raises questions of conduction vs. convection in removing the heat from the water and that leads to questions over fluid dynamics which, if memory serves, are non-linear. (and would cost a bit more than £1000 to solve). ------------- What? |
Posted By: Gamemako
Date Posted: June 30 2012 at 18:28
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Oh look, heat transfer problem! //BEGIN CHEMICAL ENGINEER// Hell if I know the answer. //END CHEMICAL ENGINEER// ------------- Hail Eris! 
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Posted By: Vompatti
Date Posted: June 30 2012 at 19:05
| Ants in the fridge! |
Posted By: Dean
Date Posted: June 30 2012 at 19:11
 ------------- What? |