https://cosmosmagazine.com/physics/mystery-solved-why-hot-water-freezes-faster-than-cold

ChrispenEvan said:

https://cosmosmagazine.com/physics/mystery-solved-why-hot-water-freezes-faster-than-cold

Interesting. An alternative way of viewing this is to consider that a beaker of water that is at 10°C and has been at this temperature for a long time is quite different to a beaker that has recently been cooled to 10°C from a somewhat higher temperature.

I don’t remember the details, but I’m pretty sure we discussed this about 100 years ago in the original SSSF.

The Rev Dodgson said:

I don’t remember the details, but I’m pretty sure we discussed this about 100 years ago in the original SSSF.

Yes, the Mpemba effect has been discussed on SSSF, but the current article provides what is probably the correct solution to the problem.

KJW said:

The Rev Dodgson said:

I don’t remember the details, but I’m pretty sure we discussed this about 100 years ago in the original SSSF.

Yes, the Mpemba effect has been discussed on SSSF, but the current article provides what is probably the correct solution to the problem.

Oh, I’m sure we did that ages ago :)

The Rev Dodgson said:

KJW said:

The Rev Dodgson said:

I don’t remember the details, but I’m pretty sure we discussed this about 100 years ago in the original SSSF.

Yes, the Mpemba effect has been discussed on SSSF, but the current article provides what is probably the correct solution to the problem.

Oh, I’m sure we did that ages ago :)

I don’t recall kurtosis being suggested as an explanation for the effect. I think I would remember that as perhaps the one way that two samples of water at the same temperature can be different.

Note that the Mpemba effect requires that there is a time at which the two samples have the same temperature. Of these two samples, the one that started from the higher temperature cools faster. But merely having started from a higher temperature can’t explain the effect unless the two samples at the same temperature remain different. And speed distribution of the water molecules provides a way in which the two samples can be different.

Interestingly, the sample that cooled the fastest cools the fastest. This enables the effect to be maintained throughout the entire cooling process, whereas the opposite effect would not be maintained due to the negative feedback
.

The Rev Dodgson said:

I don’t remember the details, but I’m pretty sure we discussed this about 100 years ago in the original SSSF.

Yes. Some of us even did the experiment, most (but not all) finding that the cold water froze first. It would appear to depend on various factors.

KJW said:

The Rev Dodgson said:

KJW said:

Yes, the Mpemba effect has been discussed on SSSF, but the current article provides what is probably the correct solution to the problem.

Oh, I’m sure we did that ages ago :)

I don’t recall kurtosis being suggested as an explanation for the effect. I think I would remember that as perhaps the one way that two samples of water at the same temperature can be different.

Note that the Mpemba effect requires that there is a time at which the two samples have the same temperature. Of these two samples, the one that started from the higher temperature cools faster. But merely having started from a higher temperature can’t explain the effect unless the two samples at the same temperature remain different. And speed distribution of the water molecules provides a way in which the two samples can be different.

Interestingly, the sample that cooled the fastest cools the fastest. This enables the effect to be maintained throughout the entire cooling process, whereas the opposite effect would not be maintained due to the negative feedback
.

—-

Where did the extra energy go?

KJW said:

Interestingly, the sample that cooled the fastest cools the fastest.

AMAZING

One thing that I think would be interesting is the extent to which the effect applies to other substances. In particular, I curious about whether hydrogen-bonding has an effect.

dv said:

KJW said:

Interestingly, the sample that cooled the fastest cools the fastest.

AMAZING

It is if one looks beyond the tautology. ;-)

tauto said:

Where did the extra energy go?

The environment.

It’s -1°C at the moment.

kii said:

It’s -1°C at the moment.

Wrong, but sort of right.

kii said:

kii said:

It’s -1°C at the moment.

Wrong, but sort of right.

You’re feeling pretty cool at the moment?

I don’t believe the Mpemba effect exists.
It’s just journalese.

“Six Year Old Uneducated Mongolian Girl Builds Worlds First Fusion Reactor in Yurt”

That one would get a lot of clicks I reckon.

“None of the explanations have been entirely convincing. Indeed, a recent study concluded “somewhat sadly” that it could find no evidence the effect even exists.”

And this Spanish experiment was a computer simulation not real world.
I’ll have no truck with it.

Peak Warming Man said:

“None of the explanations have been entirely convincing. Indeed, a recent study concluded “somewhat sadly” that it could find no evidence the effect even exists.”

And this Spanish experiment was a computer simulation not real world.
I’ll have no truck with it.

that is why i added the maybe to the thread title.

ChrispenEvan said:

Peak Warming Man said:

“None of the explanations have been entirely convincing. Indeed, a recent study concluded “somewhat sadly” that it could find no evidence the effect even exists.”

And this Spanish experiment was a computer simulation not real world.
I’ll have no truck with it.

that is why i added the maybe to the thread title.

I did notice the word left hanging.

Peak Warming Man said:

And this Spanish experiment was a computer simulation not real world.

And a grossly simplified one at that.

Which is not to say it shouldn’t be trucked, but I do this the journalistic habit of saying everyone else never had a clue and these guys totally solved it is going a bit far.

Peak Warming Man said:

“None of the explanations have been entirely convincing. Indeed, a recent study concluded “somewhat sadly” that it could find no evidence the effect even exists.”

And this Spanish experiment was a computer simulation not real world.
I’ll have no truck with it.

heh, says the guy who uses CAD programs to design things…

poikilotherm said:

Peak Warming Man said:

“None of the explanations have been entirely convincing. Indeed, a recent study concluded “somewhat sadly” that it could find no evidence the effect even exists.”

And this Spanish experiment was a computer simulation not real world.
I’ll have no truck with it.

heh, says the guy who uses CAD programs to design things…

I think you’ll find that any half way decent engineer works on the basis that all computer analyses are wrong.

The Rev Dodgson said:

poikilotherm said:

Peak Warming Man said:

“None of the explanations have been entirely convincing. Indeed, a recent study concluded “somewhat sadly” that it could find no evidence the effect even exists.”

And this Spanish experiment was a computer simulation not real world.
I’ll have no truck with it.

heh, says the guy who uses CAD programs to design things…

I think you’ll find that any half way decent engineer works on the basis that all computer analyses are wrong.

FMD, and the engineer themselves is usually out by an order of magnitude…how does anything stay upright…

poikilotherm said:

FMD, and the engineer themselves is usually out by an order of magnitude…how does anything stay upright…

Because engineers make sure the error is in the right direction.

It’s actually often quite a bit less than an order of magnitude as well, but that’s not the important bit.