R. A. Hettinga (2004-03-31 16:41Z) wrote:
At 10:26 AM -0500 3/31/04, Trei, Peter wrote:
* Evaporating LPG (liquids do not 'sublimate')...
As for "sublimate", when you toss a cup of boiling water into the air at extremely cold temperatures it converts straight into a gas, all at once. That's what I was talking about. A chemist I bumped into with that story called it sublimation, and when I said I thought "sublimate" was meant for solids only, he said no, that instantaneous conversion to a gas is sublimation whether origin state is a solid or liquid.
I very seriously doubt that. That "chemist" sounds full of shit. Boiling, evaporation, condensation, sublimation, melting, and freezing have nothing to do with the speed at which the phase change occurs. They refer to the qualitative aspect of state changes, notably the beginning, (transition,) and ending states. Sublimation is solid->gas with no intervening liquid state, that state being impossible due to prevailing pressure/temperature conditions. Haven't you ever seen a phase diagram? Furthermore, can you please explain how boiling water could change phase into a gas "all at once"? It takes energy for a compound to change to gas state, genius. Where's it going to get that energy, particularly when the surrounding air is at "extremely cold temperatures"? No macro-level events happen "instantaneously" in any reasonable sense of the word. Increase in atomic motion can only happen due to applied forces, and acceleration takes time. Even if one of those damned 50MT Russian thermonuclear bombs went off 100m away, a glass of water wouldn't vaporize instantaneously. -- "If you don't do this thing, you won't be in any shape to walk out of here." "Would that be physically, or just a mental state?" -Caspar vs Tom, Miller's Crossing