This is such a frustrating article, given the lack of a lot of technical information that would make it so much more worthwhile. Is the water from the same source? How was the initial temperature difference established? What is the degree of termperature difference? What controls are being implemented on quantity of water? Exactly what do they mean by faster (ie: stick them in the freezer at the same moment and see which one forms ice first? Formation of first visible crystal/full surface freeze/solid freeze of entire quantity? Freezing at a higher temperature?)? Are the temperatures being monitored throughout the process? Has the given water been previously frozen? Boiled? Grr. Science, in general, requires a lot of details to be specified.
Hate to be a wet blanket (hot or cold), but the laws of thermodynamics haven’t been repealed yet.
All other things being equal, cold water freezes faster than hot water.
Take a given amount of liquid water. As far as its temperature at that moment, the water molecules have no “memory” of how it got to that temperature. In other words, knowing that a liter of water in a beaker is now 4 C tells you nothing about whether it used to have a temperature of 1 C or 99 C. Ten minutes, hours, or years ago.
For water at 99 C to start to freeze at around 0 C, some time has to pass as it cools past, say, 4 C. Thus, take two identical beakers with liquid water, one at a higher temperature and one at a lower temperature, and you can predict with confidence which will freeze first.
It’s at the margins of “all other things being equal” that this conversation has some legs. There are hypotheticals one can evoke:
–the warmer container losing water mass to evaporation
–minerals precipitating
–changing the solutes to promote supercooling
–and more (follow the links in the link).
But now, this isn’t really addressing the question “Why does hot water freeze faster than cold water?â€? It’s more “What factors might, under special circumstances, cause heating to change the nature of an aqueous solution to cause it to freeze faster than a similar solution that hadn’t been heated?”
You can deduce that discussion of question was a favorite parental torment as I was growing up!
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June 3rd, 2006 at 7:30:08 am
Interesting. You would have thought this would have been figured out a long time ago because it makes perfect sense.
June 3rd, 2006 at 9:38:27 am
There is only one way that hot water freezes faster than cold water
- In heating the water, you boil off enough of it to make fewer molecules to freeze
June 3rd, 2006 at 2:08:40 pm
This is such a frustrating article, given the lack of a lot of technical information that would make it so much more worthwhile. Is the water from the same source? How was the initial temperature difference established? What is the degree of termperature difference? What controls are being implemented on quantity of water? Exactly what do they mean by faster (ie: stick them in the freezer at the same moment and see which one forms ice first? Formation of first visible crystal/full surface freeze/solid freeze of entire quantity? Freezing at a higher temperature?)? Are the temperatures being monitored throughout the process? Has the given water been previously frozen? Boiled? Grr. Science, in general, requires a lot of details to be specified.
June 4th, 2006 at 7:37:13 am
Hate to be a wet blanket (hot or cold), but the laws of thermodynamics haven’t been repealed yet.
All other things being equal, cold water freezes faster than hot water.
Take a given amount of liquid water. As far as its temperature at that moment, the water molecules have no “memory” of how it got to that temperature. In other words, knowing that a liter of water in a beaker is now 4 C tells you nothing about whether it used to have a temperature of 1 C or 99 C. Ten minutes, hours, or years ago.
For water at 99 C to start to freeze at around 0 C, some time has to pass as it cools past, say, 4 C. Thus, take two identical beakers with liquid water, one at a higher temperature and one at a lower temperature, and you can predict with confidence which will freeze first.
It’s at the margins of “all other things being equal” that this conversation has some legs. There are hypotheticals one can evoke:
–the warmer container losing water mass to evaporation
–minerals precipitating
–changing the solutes to promote supercooling
–and more (follow the links in the link).
But now, this isn’t really addressing the question “Why does hot water freeze faster than cold water?â€? It’s more “What factors might, under special circumstances, cause heating to change the nature of an aqueous solution to cause it to freeze faster than a similar solution that hadn’t been heated?”
You can deduce that discussion of question was a favorite parental torment as I was growing up!