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Freezing Speed of Hot Versus Cold Water

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Nominal Animal:

--- Quote from: magic on February 21, 2022, 10:51:13 am ---That makes no sense.
--- End quote ---
Then read the linked paper.

magic:
It's not the paper which made the statement that two samples at the same momentary temperature are conducting different amount of heat through (presumably) identical containers to (presumably) identical external environment. That's a statement about containers, not about water.

Nominal Animal:

--- Quote from: magic on February 21, 2022, 04:01:19 pm ---It's not the paper which made the statement that two samples at the same momentary temperature are conducting different amount of heat through (presumably) identical containers to (presumably) identical external environment. That's a statement about containers, not about water.

--- End quote ---
Sigh.

Here's a snippet from the abstract of the Zhang et al. paper:

--- Quote ---Numerical reproduction of observations, shown herewith, confirms that water skin supersolidity [Zhang et al., Phys. Chem. Chem. Phys., DOI: 10.1039/C1034CP02516D] enhances the local thermal diffusivity favoring heat flowing outwardly in the liquid path. Analysis of experimental database reveals that the hydrogen bond (O:H–O) possesses memory to emit energy at a rate depending on its initial storage. Unlike other usual materials that lengthen and soften all bonds when they absorb thermal energy, water performs abnormally under heating to lengthen the O:H nonbond and shorten the H–O covalent bond through inter-oxygen Coulomb coupling [Sun et al., J. Phys. Chem. Lett., 2013, 4, 3238]. Cooling does the opposite to release energy, like releasing a coupled pair of bungees, at a rate of history dependence. Being sensitive to the source volume, skin radiation, and the drain temperature, the Mpemba effect proceeds only in the strictly non-adiabatic ‘source–path–drain’ cycling system for the heat “emission–conduction–dissipation” dynamics with a relaxation time that drops exponentially with the rise of the initial temperature of the liquid source.
--- End quote ---

Note the part where it mentions "Cooling [releases] energy, [...] at a rate of history dependence"?

The skin supersolidity is a related phenomenon discussed for the last decade or so, starting at Sun, et al. "Density, Elasticity, and Stability Anomalies of Water Molecules with Fewer than Four Neighbors". J. Phys. Chem. Lett. 2013, 4, 15, 2565–2570. https://doi.org/10.1021/jz401029z.

CatalinaWOW:

--- Quote from: magic on February 21, 2022, 10:51:13 am ---
--- Quote from: Nominal Animal on February 21, 2022, 12:06:53 am ---To simplify what happens in the real Mpemba effect, is that the liquid at hand is far from an equilibrium state, and because of recently been at much higher temperature, can lose heat energy much faster than the same liquid at the same temperature in an equilibrium state would.  Simply put, the recently-hot liquid has smaller heat capacity.  (The reality is more interesting, especially when the sample starts getting nearer to an equilibrium state of the heat bath, as localized heating can often be detected due to the latent heat.  But close enough for an intuitive understanding, the interesting parts and the actual mechanism, are more like technical details.)

If we had some kind of device or meter that could measure the net energy flow between the heat bath (freezer) and the (originally liquid) sample, we'd find that at the same temperature, the energy flow from the recently-hot sample to the heat bath is higher than for the sample that was not originally that hot.
--- End quote ---
That makes no sense. You are now making claims about the container or surrounding environment having higher thermal conductivity because it "knows" something about the water inside.

Reduced heat capacity means that at the same temperature and the same energy flow, dT/dt is faster. Not quite as you explained it.

Another explanation you could reasonably attempt is increased thermal conductivity of water, i.e. less internal gradient across its volume.

--- End quote ---

The way I read Nominal's comments you have hit upon what he is saying.  The water loses heat faster.  Which would indeed slow heat transfer through the container.  But if the heat transfer through the container is not the dominant term you get the observed effect.  Remember that it is observed and repeatable (albeit with care and difficulty).  Arguments about possibility are just silly unless you are invoking experimental error.  That invocation requires supporting data just as anything else would.  Nominal has provided a credible theory, which may or may not be what is really going on, but can be modelled and fits the data.

m k:
Take hot enough water and sling it up to cold enough air and you get ice dust.
If you're under and temperature difference is not enough you'll get wet.

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