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Freezing Speed of Hot Versus Cold Water

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IanB:

--- Quote from: Nominal Animal on February 23, 2022, 03:59:08 am ---This thread is making me really depressed, to be honest.  So much "I don't believe you, because it is not how I believe things to be", instead of just checking out the peer-reviewd articles and studies by actual chemists and physicists.
--- End quote ---

I'm not sure why you keep bringing up "peer reviewed", as if it conveys anything? There are many errors and omissions in published articles, and even plain bullshit in some cases.

If you can link to, or reference, one credible experiment where such an effect has been observed, then we can have a conversation.

So far in this thread, you have linked to articles describing mathematical and computer models that suggest, given suitable conditions, such an effect might be observed. This is not evidence, it is speculation.

Nominal Animal:

--- Quote from: IanB on February 23, 2022, 04:30:50 am ---There are many errors and omissions in published articles, and even plain bullshit in some cases.
--- End quote ---
Point a single one, and stop bullshitting by making unfounded claims, and we can have an useful conversation.

What you have been posting, isn't science: it is assertion of unfounded beliefs.

IanB:

--- Quote ---We conclude, somewhat sadly, that there is no evidence to support meaningful observations of the Mpemba effect.
--- End quote ---

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5121640/#:~:text=We%20conclude%2C%20somewhat%20sadly%2C%20that%20there%20is%20no%20evidence%20to%20support%20meaningful%20observations%20of%20the%20Mpemba%20effect.

bdunham7:

--- Quote from: Nominal Animal on February 23, 2022, 03:59:08 am ---Ha, ha.  Forgot about total energy?  You know, the electricity or fuel you pay for when using snow machines?

That was a pretty dumb post from you, I must say...

This thread is making me really depressed, to be honest.  So much "I don't believe you, because it is not how I believe things to be", instead of just checking out the peer-reviewd articles and studies by actual chemists and physicists.

Do you not realize when your arguments are not science, but religion?  Dammit, I'm out.

--- End quote ---

I've been avoiding this debate because I don't want to get sucked into another waste of time, but I now have an irresistible urge to call you out as a drama queen here.  You've taken a novel but arcane corner-case that might actually be interesting to a few people--including maybe even me-- and waved around a 'peer-reviewed' article that may or may not be meritorious but has a clickbaity title using 'Mpemba'.  To me, Mpemba is ice cubes in a freezer, period.  I realize he 'discovered' the effect making ice cream, but the ultimate question for me is whether I should use hot or cold water in my ice cube tray.  Go ahead, call me simple. If you bring up other situations that have obvious differences and claim they are somehow analogous, you should be ashamed of yourself considering how you claim to represent objective truth and reason.

My snow machine comment wasn't dumb, it was straight to the point.  When you toss boiling water in the air, the difference between that and cold water is not that the heat capacity of the hot water is temporarily (and drastically) reduced nor that some characteristic of the water has changed so as to reduce the enthalpy of ice formation from it.  The difference that does matter is resolved by the (non-heated) snow machine when it atomizes the water.  I think that neither the effect in your peer reviewed article nor in the snow video are going to matter in a more typical Mpemba experiment where you might take 90C and 10C water and cool it in a -20C freezer to equilibrium.  That--which the OP in this thread unfortunately did not do as he terminated the experiment too early--is where I believe you simply don't see the effect, or if you do it is due to other factors for which I'm not aware of any real consensus.  The PCCP article appears to address this, but I didn't read it in any detail. 

I think the whole issue can be simplified into two broad questions: 

If you form ice from hot and cold samples and cool it to some temperature well below freezing and you were to observe the Mpemba effect by the hot sample leading the way, is that due to the hot sample releasing less energy (less enthalpy) or due to the transfer of heat happening faster (or both)? 

If you observe the Mpemba effect, then at the end after they are cooled to say -20C, are the two samples in the same or equivalent state at the end with regard to enthalpy (and entropy) or are they in two different states?  So perhaps if I use hot water to make ice faster, that ice won't have as much cooling power?   ???

One thing to keep in mind is that if you start with a 90C and a 10C sample, classic assumptions lead you to the conclusion that the hot sample will need to release approximately twice the heat to form ice.  That's a big difference to account for.

Nominal Animal:

--- Quote from: bdunham7 on February 23, 2022, 05:14:19 am ---I've been avoiding this debate because I don't want to get sucked into another waste of time, but I now have an irresistible urge to call you out as a drama queen here.
--- End quote ---
Fine.  I've downgraded my opinion of you to "too stupid to interact with".  You're welcome; the ignore list functionality is there for a reason.

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