# wrote on Nov 18
th, 2013 at 2:46pm:
Chimp_Logic wrote on Nov 17
th, 2013 at 8:35pm:
# wrote on Nov 17
th, 2013 at 6:31pm:
Chimp_Logic wrote on Nov 17
th, 2013 at 6:07pm:
... how does one discuss sublimation without referring to a pressure-temperature phase diagram?
...
Experience?
You're saying that, in theory, ice cannot sublime at standard pressure. I'm pointing out that,
in practice, it does.
Try this experiment:
- put a naked ice cube in a freezer (a freezer with a fan to circulate the cold will work best);
- come back in a month or two and you will find that the cube is measurably smaller.
What do you think happened to the ice that's gone missing?
is this a closed system?
1
why do you need circulating air?
2
what temperature is the air?
3
What humidity is in the freezer?
4
Do you open the door during the few months you conduct this meticulous experiment?
5
Are the seals on the freezer perfect?
6
where do you think your little ice cube is located on this phase diagram?
7
Who are you?
8
Chimp, you're evidently struggling to rationalise your blunder.
1
As closed as any real-world freezer.
2
Did I say it was necessary?
3
As I said elsewhere, most freezers are set at around -18C.
4
What would be the humidity in any domestic freezer? Probably a good deal higher than Antarctica, I'd guess.
5
Why would I?
6
Is anything?
7
No idea. I'm not pretending to pontificate on science. Just reporting real world experience.
8
Myself.
Are you honestly saying that you've never noticed that ice cubes left in a freezer slowly sublime? That foods inadequately sealed lose their moisture in a freezer (AKA freezer burn)?
On another tack: can water vaporise below its boiling point? If so, how? If not, how come it does?
who am I talking with now?
explain the mechanism whereby ice can undergo sublimation at atmospheric pressures.
youre not going to discuss your answer with muso and start to waffle on about monolayers of water without really explaining anything - AGAIN?
(the boiling point of water is also dependent ont eh ambient pressure - so you can get water to boil at room temperature if you like, by decreasing the pressure - but that's the point, you change the PRESSURE. You are stating that water can undergo sublimation at atmospheric pressures, two orders of magnitude higher than the Triple Point pressure. Explain the mechanism muso)
# can you see how the boiling point decreases on this graph as you lower the ambient pressure?
P-T phase diagrams are very useful tools in describing basic science don't you think?
Now explain your complicated pseudo-sublimation process at pressures above the Triple Point pressure