Boiling water with Ice
Boiling water with ice
This is a jar full of only water (liquid and vapor). It boils at any temperature when you apply something cold enough to the top, like ice.
cross-posted from: https://lemmy.sdf.org/post/2697716
I put water in a jar and sealed it while it was boiling, and now it boils at any temperature. Super fun demo to try.
I've read the video description several times, and I still don't understand. This bit in particular:
Whenever there is a heat transfer from the bulk water to the lid (condensing the vapor), the water boils, no matter the absolute temperature.
Is the idea that water condenses at a lower energy state, so when cold is applied, the water vapor turns to liquid? If so, what does that have to do with the water boiling?
I don't understand.
When the water vapor inside the jar comes in thermal contact with the ice outside, it condenses and precipitates. This decreases the vapor pressure inside the jar, which then causes the water to boil.
Boiling is not just a temperature-based phenomenon, it's also a pressure-based one: a water body maintains an equilibrium between liquid water and water vapor right above its surface. If you remove the water vapor from above the surface, it decreases the vapor pressure and shifts the equilibrium away from the liquid state, which is essentially boiling. Note that this is different from evaporation since the liquid water is not using heat from an external source to vaporize. You can also see this in daily life, for example, in that water boils at a different temperature on mountains due to pressure difference.
That is a cool chemistry experiment! Thank you for sharing!
Now I wonder if the pressure inside is low enough that you could reach the water's triple point If you cool it down to 0,01°C
Yes definitely. The pressure will drop along the vapor pressure curve all the way to the triple point, gently boiling all the way if you remove the heat from the vapor and not directly from the water.
Hmm. I wonder if you could make a higher-quality vacuum this way by adding a getter. You'd think it would still be safe-ish with reactive metals because bulk liquid water never needs to be anywhere near the chamber (air will remove heat too, just somewhat slower).
