This was known by many Antarctic scientists before 1963. I remember my dad telling me you could throw boiling water into the air and it would freeze into millions of tiny ice crystals before reaching the ground, but that the same wasn't true of cold water. I think he said it was due to thermal inertia.
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"Thermal inertia" is more formally known as specific heat capacity or volumetric heat capacity, which is a substance's resistance to change in temperature.
It's similar to (but different from) mechanical inertia, which is an object's resistance to change in velocity.
The latter includes the concept of momentum, that an object with nonzero velocity resists changing it's velocity. There is no such thing as thermal momentum, remove the temperature differential and a thermally uniform substance that's changing temperature at 10 degrees per second will stop getting colder instantly. For related reasons, there's no overshoot when you reach equilibrium, either.
That sounds like a totally DIFFERENT effect, almost certainly caused by droplet size.
It could be the same.
I always learned the explanation as: 1. Cool to freezing via evaporation. Because this goes as T^4, the time difference is negligible to reach 0°C. But...hot water loses more volume. 2. Freeze, bit now you need less energy to freeze less material.
I did this at home, and the simple check worked: volume was lower in the frozen hot water.
This explanation might be wrong! But it works out in simple tests and mathematically.
Many Canadians have known about this for a while, here is what it looks like...
I’ve done it before in -40C weather and the liquid water doesn’t freeze, just the vapor coming off.
Same effect as seeing your breath in cold weather.
It definitely can all freeze, -40 (conveniently the same in F and C) is about the point where the trick starts working well, but the effect gets more pronounced as the temperature goes lower.
I guess it depends on what you mean by “all”?
I did it with a cup of boiling water and most of it fell back down as water.
If it's cold enough, and you throw a cup of boiling hot water in to the air, every bit of the thrown water will turn in to something like snow, and no liquid comes back down. It seems like the size of the flung water droplets is important, like if the water is thrown more vigorously the effect is more pronounced.
I wintered at the South Pole in 2014, the year the ALS Ice Bucket Challenge was a big thing. One of our crew did it, outside. We discovered a similar effect: when it's even colder out, maybe -80s F: ice water makes what looks like a cloud of steam - in the video (sorry, can't find it quickly) it looked a bit like he was cheating.
Must depend on technique. I could never get it to completely freeze, but the coldest was -40C.
I could see if you can disperse it into small enough droplets it would work.