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Iron as a gas.

  1. Feb 20, 2014 #1
    The way I understand plasma is that is almost a gas except some of the electrons of separated from the nuclei entirely making positively charged. Is there a temperature in which Iron is by definition a gas, and not a plasma?

    Also, can something like a noble gas become a solid?
  2. jcsd
  3. Feb 20, 2014 #2
    Sure. Neon, for instance turns solid at about 24.5 K.
  4. Feb 20, 2014 #3
    Would this have to be under pressure or could it be 24.5 kelvin in a vacuum and still be a solid?

    Also nice job on the 700 posts :D
  5. Feb 20, 2014 #4
    That's at standard pressure. Only helium does not turn solid at standard pressure. If memory serves, a minimum of 20 atmospheres is required (and extremely low temperatures) to produce solid helium
  6. Feb 20, 2014 #5
    The critical pressure of helium is 2.24 atm., so the equilibrium vapor pressure at the solidification temperature is lower than this.

  7. Feb 21, 2014 #6


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    Staff: Mentor

    There is no clear border between gas and plasma - if you increase the temperature, you just increase the fraction of ionized atoms.
    The first ionization energy of iron is 8 eV and iron becomes a gas at ~3000K or ~1/4 eV, at this temperature the fraction of ionized atoms is low (but still existent).

    Where is the relation between the critical pressure (=gas/liquid related) and the solid phase?

    Here is a phase diagram of helium
  8. Feb 21, 2014 #7
    Yikes. I've never seen a phase diagram like this before. I guess you learn something new every day. Thanks.

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