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Author Topic: Can Air Freeze ?  (Read 46208 times)

neilep

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Can Air Freeze ?
« on: 18/04/2008 23:51:57 »
Dear Airologists and Breathers Of Air,

Air is my all time favourite thing to breath !..I just luff it !!

Look, here's some !!



Nice eh ?....now that's quality air !

Could it get so cold that the very air in front of your face could freeze ?...or is that me just being a silly sheepy ?

ewe see, I just don't know !!

do ewe ?

Hugs and shmishes


Neil
Frozen Air Enquirer

xxxxxx




turnipsock

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Can Air Freeze ?
« Reply #1 on: 19/04/2008 00:07:42 »
Well you do know that you can get liquid nitrogen and air is about 80% nitrogen. I remember we had some at school, I remember leaning across and my school tie went into the liquid nitrogen with hilareous consequencies.

Supercryptid

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Can Air Freeze ?
« Reply #2 on: 19/04/2008 01:05:48 »
Yes, air can freeze. Air is composed of 21% oxtgen, 78% nitrogen, and 1% argon (roughly, since trace gases like carbon dioxide and water vapor can also be in air). Oxygen freezes at -360.9 F, nitrogen at -346.18 F, and argon at -308.7 F. Therefore, air will freeze if it gets cold enough to freeze oxygen. Such temperatures are never reached naturally on Earth.

As a matter of fact, the only substance that won't freeze at atmospheric pressure is helium. You have to put helium under higher pressure before it will freeze.

DoctorBeaver

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Can Air Freeze ?
« Reply #3 on: 19/04/2008 06:14:24 »
As a matter of fact, the only substance that won't freeze at atmospheric pressure is helium. You have to put helium under higher pressure before it will freeze.

But doesn't pressurising it cause it to heat up?

lyner

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Can Air Freeze ?
« Reply #4 on: 19/04/2008 09:04:04 »
Only because you have done work on it. It will soon cool down again and then you can do what you want with it.

science_guy

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Can Air Freeze ?
« Reply #5 on: 20/04/2008 02:43:51 »
well, there is a discrepency in the second law of thermodynamics...

it is marginally possible that the particles in the air that have a low temperature would condense at a single point (in front of your face, in your scenario).

this possibility, however, is very small.  something in the neighborhood of 1*10^-(insert high number here)

another_someone

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Can Air Freeze ?
« Reply #6 on: 20/04/2008 03:39:39 »
well, there is a discrepency in the second law of thermodynamics...

it is marginally possible that the particles in the air that have a low temperature would condense at a single point (in front of your face, in your scenario).

this possibility, however, is very small.  something in the neighborhood of 1*10^-(insert high number here)

How is this a discrepancy in the second law of thermodynamics?

The second law of thermodynamics only talks about isolated systems - what you are suggesting is not an isolated system.

The second law also merely states that entropy will tend to increase over time, it does not say it cannot momentarily reduce, only that the long term trend will be to increase.

lyner

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Can Air Freeze ?
« Reply #7 on: 20/04/2008 19:54:57 »
Quote
it does not say it cannot momentarily reduce,
Precisely; we wouldn't be here if it didn't!

science_guy

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« Reply #8 on: 20/04/2008 23:00:21 »
I was just pointing out that the temperature in are is defined in the average kinetic energy in a system.  the average suggests that there are some particles with high kinetic energy, and some with low kinetic energy.

the possibility is that the particles with low kinetic energy could condense at a single energy, thereby decreasing the temperature of that point.

but it is VERY unlikely

neilep

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Can Air Freeze ?
« Reply #9 on: 21/04/2008 15:52:04 »
Thank you all for your great posts.


lyner

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Can Air Freeze ?
« Reply #10 on: 21/04/2008 16:09:47 »
Quote
the possibility is that the particles with low kinetic energy could condense at a single energy, thereby decreasing the temperature of that point.
And a Maxwell demon would see it happen!

paul.fr

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Can Air Freeze ?
« Reply #11 on: 21/04/2008 16:30:00 »
Possibly not the answer you were after, but seeing as you opened the topic with a cloud picture...

this is a fall streak


which is a hole occurring in a cloud layer of supercooled water droplets; produced by the local freezing of some of the droplets and their coversion into fallout, frequently in a streak form. So yes...sort of...an area of a cloud can freeaze and fall from the sky, sort of like a tale by pooh bear.

this is Verga:



From Wikipedia, the free encyclopedia
Jump to: navigation, search
For the genus of grass skipper butterflies, see Virga (butterfly). See Virga (planetary geology) for virgae, a type of surface feature found on Titan.
 
Nimbostratus virga
Virga falling from AltocumulusIn meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is usually due to compressional heating, because the air pressure increases closer to the ground. It is very common in the desert and in temperate climates. It is also common in the Southern United States during summer.

Virgae can cause very interesting weather effects, because as rain is changed from liquid to vapor form, it removes heat from the air due to the high heat of vaporization of water. In some instances, these pockets of colder air can descend rapidly, creating a dry microburst which can be extremely hazardous to aviation.

Virgae also have a role in seeding storm cells whereby small particles from one cloud are blown into neighboring supersaturated air and act as nucleation particles for the next thunderhead cloud to begin forming.

Virga can produce dramatic and beautiful scenes, especially during a red sunset. The red light can be caught by the streamers of falling precipitation, and winds may push the bottom ends of the virga so it falls at an angle, making the clouds appear to have commas attached.

The word virga is derived from Latin meaning twig or branch and a popular backronym in meteorology is "Variable Intensity Rain Gradient Aloft."


neilep

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« Reply #12 on: 21/04/2008 17:15:12 »
AWESOME PAUL !!!


YOU are the Cloud Master !!

Thanks for a fascinating post !

animefreak

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Can Air Freeze ?
« Reply #13 on: 21/04/2008 20:10:56 »
the air is mainly made of nitrogen, carbon dioxide and oxygen so theoretically the air could freeze. oxgen freezes at 50.35 kelvin, nitrogen freezes at 63 kelvin and carbon dioxide freezes at 195 kelvin but any impurities in the air could affect the freezing point of air

Bored chemist

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Can Air Freeze ?
« Reply #14 on: 22/04/2008 19:32:06 »
There's a tiny trace of helium in air, about 5 parts in a million. The pressure isn't high enough for it to freeze no matter how cold it gets.

 

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