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I have observed my daughter throw a flask of near-boiling water into the air outside at -20C. The water appears to turn into "steam" which actually appears to be ice crystals. She also tried with cold-water and the result was different - the water just fell to the ground as a liquid.

I have searched online for an explanation and most are "hand waving" and I don't think explain the phenonemon correctly e.g. https://phenomena.iowapbs.org/item/throwing-boiling-water-freezing-air

I am a physicist by training and asked my colleagues. We reckong the following

  1. Water is near boiling point and has low viscosity and surface tension as compared to colder water
  2. Due to low viscosity the water has an increased tendancy over lower temperature water to break into small drops/droplets
  3. Water vapourises at the surface interface between the liquid and the air - and vapour will be at the "ambient" vapour pressure.
  4. In a closed system there would an equilibrium where vapour exists at vapour pressure above the liquid.
  5. At normal temperatures and pressures the water would fall under the effect of gravity and as the "drops" of water fall vapour would be displaced by air and, therefore, more water vapour would be produced. In the second or so it takes the water to fall some would evaporate but, ordinarily, this would be unobservable as the amounts would be negligible
  6. In the case discussed the air temperature is so low that the water vapour instantly freezes - this is known as deposition (opposite of sublimation). With this deposition the vapour pressure drops (tends to zero) and more water evaporates. This "cycle" repeats rapidly such that all the water evaporates and undergoes deposition before it has fallen to the ground.
  7. If the water temperature is too low then this "cycle" still occurs but does not happen quickly enough before the water reaches the ground.
  8. If the air-temperature is too high then there is not enough "deposition" and the effect does not occur.

So I think that this effect is driven by viscosity/surface-tension, deposition (opposite of sublimation) and air temperature. I suspect there is a threshold water temperature and also air temperature which could be determined by experimentation.

I'd like people to comment on my "theorem" which I name the "Jeffery-Moss-Beanie" effect after it's investigators

Please pull my ideas apart !

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    $\begingroup$ Try looking into the Mpemba effect, which is what you are describing. Unfortunately there is no undisputed or simple theory of why this happens. $\endgroup$
    – Matt Hanson
    Commented Dec 10 at 13:24
  • $\begingroup$ Ordinarily I think Qs like this would be off-topic as personal theories but there is actually a lot of legitimate thinking to be done on this topic. I’ve asked upvoted questions about “is this process explaining adequately this observed effect” before, and this doesn’t seem different, so +1 from me. I haven’t much to provide in terms of an answer but I hope someone else does. $\endgroup$
    – controlgroup
    Commented Dec 10 at 14:09
  • $\begingroup$ Tx. I asked as I have only seen hand-waving arguments with no real physical explanation. Hence my reasoning. It's not as simple as you first think! $\endgroup$
    – DJDJ
    Commented Dec 10 at 15:47

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