Absolute zero is -273 C and hydrogens freezing point is -259 C, is there anything that will not freeze at even -273 C?
No. Everything freezes if you get it cold enough.
Wrong. Helium does not freeze.
http://www.encyclopedia.com/html/s1/superflu.asp
http://www.unm.edu/~quantum/quantum_2003/beyondthelimits.html
I’ll have to check out your links to see how they explain this. At absolute zero, all atomic motion (brownian motion) stops. It’s hard to fathom He can remain a liquid and has no solid phase. What about at higher pressures???
A precursory reply,
- Jinx
I found a different cite saying helium can freeze, but only under high pressure as well as low temperature… on the order of 20 times atmospheric pressure
http://www.technifab.com/helium.htm
still pretty impressive though, and qualifies as ‘something that can be at absolute zero’ (or as close as is physically reachable) and still be a liquid… also something that will not freeze just from being ‘cold enough’
Yeah, but you can’t actually reach absolute zero.
As cold as you can get in the lab, and at atmospheric pressure, helium is a liquid. And a pretty funky one too.
I remember reading in a scientific magazine how at least one isotrope (or allotrope?) of Helium becomes a mono-atomic powder within a few degrees of Absolute Zero.
Actually, this isn’t quite true – rather, at absolute zero, the system goes to the state with the lowest possible energy. You’d think that this would be “all atoms not moving”, but quantum mechanics rears its ugly head & says that that’s not quite the case. (This is broadly related to the uncertainty principle.) Instead, the atoms have to be thought of as (in some sense) fluctuating around some “average position”, and it’s these fluctuations that keep helium liquid at extremely low temperatures. The reason that this doesn’t happen for any other noble gases is that these fluctuations are inversely proportional to the mass of the atoms, and only for helium do the fluctuations get large enough to keep it from freezing.
At least, that’s how it was explained to me when I took Solid State Physics last fall. Do we have any condensed-matter physicists on the SDMB, perchance?
Doesn’t it all turn into squishy blobs of Bose-Einstein condensate at absolute zero?
Here’s what the first of GaryT’s links says:
If helium refuses to become solid at 0K, what about hydrogen? I’m guessing it would act much the same way.
After Googling, I found that Helium freezes at 100 MPa at 15 K.
I assume that means 100 Mega Pascals at 15 Kelvins.
I further assume a Pascal is some unit of pressure…like a gram or kilogram per square meter or square centimeter?
Did you not see the freezing point of hydrogen listed in the OP? Helium is unique in not freezing.
Yep! And, also according to Google, 100 megaPascals = 986.923267 atmospheres of pressure.
So, a lot.
Your assumptions are correct, on both counts (and you even used “Kelvins” correctly - not the incorrect “degrees Kelvin” which drives me bonkers). A Pascal is equal to one newton per square meter of pressure, or about .000145 PSI.
Bah. I know I shouldn’t skim, yet I still do.
Anyway, why does hydrogen freeze? Is it because it will form a diatomic molecule?
Why can’t temperatures reach absolute zero? Is it because it would require absolutley no motion of the atoms which is somehow impossible? Also, I’ve heard that a theory of the end of the universe says that the universe will continue to expand until all of the available energy is used up, at which point it will just stop. Would this lack of energy eventually get to absolute zero? Or does that whole “energy is neither created nor destroyed” thing keeping absolute zero from happening?
Yes (see especally the third bullet opint). The time for which the atom could remain at such a specific energy as E=0 would be uncertain.
I know that the old adage that says that isotopes of the same element are chemically identical is not quite true for deuterium – its chemical properties are almost the same as naturally occurring (mostly protium) hydrogen but differ in reaction speed (and indeed there are a couple of reactions which hydrogen must be noodged into reactivity that deuterium just plain won’t react at any reasonable rate).
I know that Helium-3 (“tralphium,” on the nuclide-naming system) will not go superfluid at all; does it have different properties with regard to freezing than Helium-4. (BTW, does the <1% admixture of He-3 in “natural helium” affect its behavior at all at cryogenic temperatures?)
And, because I feel silly this morning, if you are in the U.K. and pressure someone into betting £100 or so, could that be described as a Pascal-wager? 
I was about to say. I remember from my AP chemistry class all those phase diagrams and how Mrs. Thompson looked positively rapturous ranting on about how the curve in water going this way instead of that meant it expanded as it froze and thus ice floated and life was possible and… </ramble>
Anyhow, they all have two dimensions: temperature and pressure. We must interpret “never” as “under no condition of temperature and pressure”.
Now, are there any such substance with no solid phase?