# The Naked Scientists Forum

### Author Topic: What happens to the volume of a gas at absolute zero?  (Read 16090 times)

#### Tintin_Triton

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##### What happens to the volume of a gas at absolute zero?
« on: 07/10/2009 14:37:51 »
By Charles'Law we know that,
v=v0+(t/273)*v0

Therefore, at 0K (lowering from 273K) the volume of the gas in question, i.e. the ideal gas, will be 0
People say that the volume does not go 0. Thus it violates the Charles' Law! Yet people say it hold at all temperatures, and say(at least my teacher does) that there can be theoretically negative volume also!

But i want to know what exactly are the changes that happen when the temperature of such low degree, and if we should put a limit to the validness of this law.

Thank you!
And may it freeze! I am melting here! 313K here at this moment....

[MOD EDIT - PLEASE PHRASE YOUR THREAD TITLES AS QUESTIONS, IN LINE WITH FORUM POLICY. THANKS. CHRIS]
« Last Edit: 07/10/2009 19:47:26 by chris »

#### lightarrow

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##### Re: What happens to the volume of a gas at absolute zero?
« Reply #1 on: 07/10/2009 14:41:11 »

#### Bored chemist

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##### Re: What happens to the volume of a gas at absolute zero?
« Reply #2 on: 07/10/2009 18:57:32 »
Since, at 0K there are no gases (because they all liquefied or froze) the point is moot.
How can you apply the gas laws where there are no gases?

#### Soul Surfer

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##### What happens to the volume of a gas at absolute zero?
« Reply #3 on: 07/10/2009 22:58:29 »
The gas laws like many similar types pf physical "law" are approximations that are valid over a particular range of conditions.  in the case of gas laws the approximation is that the gas molecules are very small compared with the total volume that the gas occupies and that the molecules interact with simple elastic collisions.  Clearly this is true for high temperatures and low pressures as the temperature falls the gas contracts (at constant pressure) and eventually the interaction energy of the molecules gets close to the energy levels that allow the gas to liquefy and/or solidify and the properties will become more non linear as as the pressure rises (at constant temperature the volume will contract until the gas molecules will be forced together to become a liquid or a solid.  about the only exception to this is superfluid helium which is always a liquid until the atoms a crushed to become a plasma even though the temperature is low.
« Last Edit: 08/10/2009 09:43:02 by Soul Surfer »

#### yor_on

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##### What happens to the volume of a gas at absolute zero?
« Reply #4 on: 07/10/2009 23:10:20 »
Well you're discussing 'infinities' here i think :)

If you could 'freeze' a gas to absolute zero then it would have no energy, right?
And without any 'energy' to it no movement/vibration right?

Then you can look at it several ways. One would be to state that it still exist as a continuous geometric shape inside Spacetime which then would allow you to disregard Heisenberg's uncertainty principle (HUP) and allow you to 'pinpoint' every condensed 'particle' in that 'soup'. The other would be to define it as 'disappearing' which then allows it to not violate HUP.

Although if 'freezing' something to that level of 'zero energy' your equipment doing it will crave a 'infinite' amount of energy doing so (think fridge and you will see what I mean).

That is as long as we are discussing processes inside Spacetime. If you're considering 'virtual photons/particles' outside Planck length and negative/positive energy you're at a different ballgame. But those processes still don't allow for that 'negative energy' overpowering our Spacetimes demand of 'positive energy'. Check out “Charting the river of time” by Ken Olum at www.fqxi.org/data/articles/Olum_Ken.pdf for his experiments on it. My guess is that there always will be a slight bias for 'positive energy' inside our Spacetime

#### lightarrow

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##### What happens to the volume of a gas at absolute zero?
« Reply #5 on: 07/10/2009 23:26:36 »
If you could 'freeze' a gas to absolute zero then it would have no energy, right?
No, there is 'zero point energy':
http://en.wikipedia.org/wiki/Zero-point_energy
<<...an atomic system at absolute zero retains an energy of ½hν.>>

#### Mr. Scientist

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##### What happens to the volume of a gas at absolute zero?
« Reply #6 on: 07/10/2009 23:30:31 »
By Charles'Law we know that,
v=v0+(t/273)*v0

Therefore, at 0K (lowering from 273K) the volume of the gas in question, i.e. the ideal gas, will be 0
People say that the volume does not go 0. Thus it violates the Charles' Law! Yet people say it hold at all temperatures, and say(at least my teacher does) that there can be theoretically negative volume also!

But i want to know what exactly are the changes that happen when the temperature of such low degree, and if we should put a limit to the validness of this law.

Thank you!
And may it freeze! I am melting here! 313K here at this moment....

[MOD EDIT - PLEASE PHRASE YOUR THREAD TITLES AS QUESTIONS, IN LINE WITH FORUM POLICY. THANKS. CHRIS]

Any value you can formulate for a particle at zero-temperatures will evaluate itself a quantity for each quantum oscillator half the given energy. So even at zero-temperatures there is still a massive amount of energy residing for any quantum oscillating system.

#### yor_on

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##### What happens to the volume of a gas at absolute zero?
« Reply #7 on: 08/10/2009 01:05:42 »
Yes Lightarrow, there is a theoretical 'zero point energy' but as Ken Olum states.

"But negative energy is hard to get and harder to keep. The cosmos is punctilious about balancing the energy books, a truth physicists recognize by referring to the ANEC, or Averaged Null Energy Condition.

The ANEC essentially says that, though you can borrow a little negative energy on your route through space-time, you wind up paying it back with the positive type.

Exotic phenomena are unlikely because they require some form of energy with a density that violates the ANEC—“they require that the total energy density be negative when we add up all the contributions over the complete path of the light ray,” as Olum describes it. Which is to say, a little trading in the energy margins is fine, but the end result will still be positive—or at least not negative enough, for long enough, over a large enough region to make any difference.

Along with Noah Graham, a Junior Faculty Fellow at Middlebury College, Olum has already shown that the ANEC still obtains between Casimir plates, even if you put holes in the plates so a photon can pass through in the most negative energy-friendly direction. “What we found was the striking result that the region near the hole always contributed enough positive energy to overwhelm the ANEC violation,” said Graham.

“This result could be a coincidence of this particular system, but it certainly suggests there is a deeper principle at work.” With Fewster and Pfenning, Olum showed that there is such a principle at work in flat space, a finding confirmed by his work with Graham. If it applies to more complex systems as well, that principle may be the barrier to time travel.“No collection of Casimir-type systems in flat space can violate the ANEC,” Olum said. “This we succeeded in showing. So the next thing to do is to try this for interacting fields, and curved space.”

So you might be right, but I'll bet you my teddy-bear you're wrong.
Not that I would have one of course :)

Well, at least it would have a blue hanky ::))
Aggh, if I had it. . Which I don't.

--

But if I mean...

--
And I see that as similar (if it would be right) to CP-violations as it is about how Spacetime can keep its existence.
http://www.physics.uc.edu/~kayk/cpviol/CP_A2a.html

« Last Edit: 08/10/2009 01:16:57 by yor_on »

#### wanhafizi

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##### What happens to the volume of a gas at absolute zero?
« Reply #8 on: 08/10/2009 03:06:11 »
I don't think it is possible to reach this temperature.

Even every corner of the space has been touched by photons/EM waves.

Probably the only place where photons haven't come in contact with is where space haven't exists yet.

But, the place where space didn't exists cannot exists, because nothing exists in nothingness. Therefore, absolute zero is never possible!

I duno...

#### Bored chemist

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##### What happens to the volume of a gas at absolute zero?
« Reply #9 on: 08/10/2009 19:08:53 »
If you could get to 0K (and you cannot) there would be no gas.

#### The Naked Scientists Forum

##### What happens to the volume of a gas at absolute zero?
« Reply #9 on: 08/10/2009 19:08:53 »