What happens if water falls from -196°C?

Answer

Dear Gabriel,

The state of a substance at a certain pressure and temperature can be read from a phase diagram (see the bottom image of the attached link: there is the phase diagram for H₂O given). If you look at this diagram, you can see that it is never possible to get water at that temperature, even if you are allowed to change the pressure. You can see this as follows: if you draw a vertical line at a temperature of -196 C, you will never intersect the green area (liquid water).

There is a phenomenon called supercooling, whereby liquids only solidify at a temperature lower than the freezing point. This process also cannot ensure that there is liquid water at -196 C, because at normal pressure this only works for a temperature down to -48 ºC. If you go below, ice will still form.

At a temperature of -196 ºC there is therefore only ice, and more specifically two types: I_c-ice cream and I_h-ice. I_hice cream is the ‘normal’ ice cream we know from our daily lives. I_cice is a metastable variant, which means it will transform into I_h-ice. The difference between the two types is in the structure of the ice crystals. Both variants have approximately the same mass density.

In conclusion: if H₂O falls from -196 C, it is likely to break.