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Bogie
2008-Jan-19, 04:25 PM
Why is liquid helium (http://www-safety.deas.harvard.edu/services/helium.html) colder than liquid hydrogen (http://www-safety.deas.harvard.edu/services/hydrogen.html)?

antoniseb
2008-Jan-19, 04:44 PM
Because Hydrogen molecules have stronger van der waals forces than Helium.

01101001
2008-Jan-19, 04:48 PM
Why is liquid helium (http://www-safety.deas.harvard.edu/services/helium.html) colder than liquid hydrogen (http://www-safety.deas.harvard.edu/services/hydrogen.html)?

Couldn't tell you why, but boiling point clearly doesn't go by atomic number, elements sorted by boiling point (http://www.science.co.il/PTelements.asp?s=BP):


36 83.8 Krypton Kr -157 -153 1898 18 [Ar] 3d10 4s2 4p6 13.9996
8 15.9994 Oxygen O -218 -183 1.43 46.71 1774 16 [He] 2s2 2p4 13.6181
18 39.948 Argon Ar -189 -186 1894 18 [Ne] 3s2 3p6 15.7596
9 18.9984 Fluorine F -220 -188 1.7 0.029 1886 17 [He] 2s2 2p5 17.4228
7 14.0067 Nitrogen N -210 -196 1.25 1772 15 [He] 2s2 2p3 14.5341
10 20.1797 Neon Ne -249 -246 1898 18 [He] 2s2 2p6 21.5645
1 1.0079 Hydrogen H -259 -253 0.09 0.14 1776 1 1s1 13.5984
2 4.0026 Helium He -272 -269 1895 18 1s2 24.5874

grant hutchison
2008-Jan-19, 04:52 PM
What antoniseb says. I think perhaps there's a useful word omitted, though: hydrogen molecules have stronger van der Waals forces than helium atoms.
Because helium is a noble gas, it hangs around as individual atoms, and is therefore a smaller fundamental unit. It produces correspondingly smaller van der Waals forces, which are generated by transient unevenness of charge distribution.

Grant Hutchison

Bogie
2008-Jan-19, 05:03 PM
Thanks to all three of you for the quick response. A quick look at van der waals forces says they are the totality of intermolecular forces and are weaker than chemical bonding.

It is interesting about the boiling point, and about the inert noble gas.

Bogie
2008-Jan-19, 05:06 PM
I noticed that liquid helium is colder than the cosmic microwave background. Is it the coldest we can get something?

grant hutchison
2008-Jan-19, 05:23 PM
I noticed that liquid helium is colder than the cosmic microwave background. Is it the coldest we can get something?Laboratories routinely go colder than that: into the microkelvin range, IIRC.
Edit: Oops. I see they're down below a nanokelvin now.

Grant Hutchison

01101001
2008-Jan-19, 05:27 PM
I noticed that liquid helium is colder than the cosmic microwave background. Is it the coldest we can get something?

Why wouldn't that be, for instance, something like frozen solid helium -- or whatever atoms were used to attain the record cold (Wikipedia (http://en.wikipedia.org/wiki/Absolute_zero))


In September 2003, MIT announced a record cold temperature of 450 pK, or 4.5 × 10-10 K in a Bose-Einstein condensate of sodium atoms.

Bogie
2008-Jan-19, 05:53 PM
Yikes, nanokelvins. Burrrrrrrrrrr. Were going to have to find little winter jackets for those poor babies. I did see something about that. Was it an ion of helium?


In September 2003, MIT announced a record cold temperature of 450 pK, or 4.5 × 10-10 K in a Bose-Einstein condensate of sodium atoms.Is is funny you mention that. I have another Q&A thread about the BEC and have been struggling with a response but haven't been able to quite get to what is lurking there in my feeble brain.

I wonder what gas they were using when they isolated the BEC? Can sodium atoms be a gas?

01101001
2008-Jan-19, 06:13 PM
I wonder what gas they were using when they isolated the BEC? Can sodium atoms be a gas?

Is not the BEC its own form of matter, fluid-like, but none-of-the-above? Wikipedia (http://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate)


A Bose–Einstein condensate (BEC) is [B]a state of matter formed by a system of bosons confined in an external potential and cooled to temperatures very near to absolute zero (0 kelvin or -273.15 °C).

Bogie
2008-Jan-19, 10:13 PM
elements sorted by boiling point (http://www.science.co.il/PTelements.asp?s=BP):
Quote:
36 83.8 Krypton Kr -157 -153 1898 18 [Ar] 3d10 4s2 4p6 13.9996
8 15.9994 Oxygen O -218 -183 1.43 46.71 1774 16 [He] 2s2 2p4 13.6181
18 39.948 Argon Ar -189 -186 1894 18 [Ne] 3s2 3p6 15.7596
9 18.9984 Fluorine F -220 -188 1.7 0.029 1886 17 [He] 2s2 2p5 17.4228
7 14.0067 Nitrogen N -210 -196 1.25 1772 15 [He] 2s2 2p3 14.5341
10 20.1797 Neon Ne -249 -246 1898 18 [He] 2s2 2p6 21.5645
1 1.0079 Hydrogen H -259 -253 0.09 0.14 1776 1 1s1 13.5984
2 4.0026 Helium He -272 -269 1895 18 1s2 24.5874




Couldn't tell you why, but boiling point clearly doesn't go by atomic number, elements sorted by boiling point (http://www.science.co.il/PTelements.asp?s=BP):Thank you for the table and link. Your statement about the boiling point not directly related to the atomic number made me wonder if there was a relationship between the boiling point and some combination of data per atom of gas from the periodic table.

From the list you copied and pasted to your post, I tried to find a relationship.

They all follow my formula even when I add the next two gasses, Xe and Rn. But when I add Cl the formula isn't worth diddily :(.

If you sort the gasses using the atomic number minus the preponderance of neutrons (neutrons minum protons) you get a list where all of the nobel gasses fall in order by boiling point and all the non-nobel gasses fall in order by boiling point except when you add Chlorine.

Then if you want to get the whole list to fall in order by boinling point, divided the noble gas results by 2 and add 1. (It works with the excepton of Cl).


Symbol Noble? Boils@ Proton Neutron P-(N-P) /2,add1 Bogie'sformula
Cl Not -35 17 18 16 Not 16.0
Rn noble -62 86 136 36 19 19.0
Xe noble -108 54 77 31 16.5 16.5
Kr noble -153 36 48 24 13 13.0
O Not -183 8 8 8 Not 8.0
Ar noble -186 18 22 14 8 8.0
F Not -188 9 10 8 Not 8.0
N Not -196 7 7 7 Not 7.0
Ne noble -246 10 10 10 6 6.0
H Not -253 1 0 2 Not 2.0
He noble -269 2 2 2 2 2.0


I'm not saying this is a bid deal, not even a little deal, and I know all the reasons why there is no reason for this to mean anything. I just found it interesting. Is there something about Chlorine that would make it different from the other gasses and therefore require a change to the formula?

RussT
2008-Jan-19, 10:23 PM
I watched with facination and a healthy sense of skepticism the Nova program..."The Race To Absolute Zero". Google it...I could not find a written transcript for it...they were all vids.

I do not know much of the history of how Einstein and Bose wound up working on this, but the Einstein/Bose Condensate wound up being a prediction.

My healthy skepticism is not about the work...cooling the gas of oxygen to make it a liquid and then using that cooled liquid oxygen to cool the next gas? to make that a liquid, and then using that liquid to cool the next getting to liquid Hydrogen (the guy that did this really got short-changed when the last guy went from liquid Hydrogen to liquid Helium!)...

BUT, my skepticism is about what man can do in the laboratory VS what is really happening in nature itself.

Bogie, you are exactly on the right track to bring in the CMB, and if I had more time to be responding, I was going to compliment you on many of the very fine questions you have been asking.

SO, the question becomes...where in nature/out in space/in all the gas nebulae, does nature have any processes that can turn any of the noble gases into liquid...are there any processes that can "Cool" those gases below the CMB to actually accomplish what mankind can in the lab???

Bogie
2008-Jan-19, 10:38 PM
I watched with facination and a healthy sense of skepticism the Nova program..."The Race To Absolute Zero". Google it...I could not find a written transcript for it...they were all vids.

I do not know much of the history of how Einstein and Bose wound up working on this, but the Einstein/Bose Condensate wound up being a prediction.

My healthy skepticism is not about the work...cooling the gas of oxygen to make it a liquid and then using that cooled liquid oxygen to cool the next gas? to make that a liquid, and then using that liquid to cool the next getting to liquid Hydrogen (the guy that did this really got short-changed when the last guy went from liquid Hydrogen to liquid Helium!)...

BUT, my skepticism is about what man can do in the laboratory VS what is really happening in nature itself.

Bogie, you are exactly on the right track to bring in the CMB, and if I had more time to be responding, I was going to compliment you on many of the very fine questions you have been asking.

SO, the question becomes...where in nature/out in space/in all the gas nebulae, does nature have any processes that can turn any of the noble gases into liquid...are there any processes that can "Cool" those gases below the CMB to actually accomplish what mankind can in the lab???Thank you RussT. I'm watching it now, and there is a transcript (http://www.pbs.org/wgbh/nova/zero/program.html).