Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Can a liquid or solid plasma exist?

  1. Oct 27, 2018 #1
    Excuse me if this is naive question :oldsmile:

    Plasma is gas where all atoms are ionized. I would like to know if liquid or solid plasma can exist. Let’s take chemical element Lithium, its atom has got 3 electrons and Lithium’s crystal lattice is arranged like this:
    So, if we somehow (but not with high temperature, otherwise this element will be melted) remove all 3 electrons from Lithium’s atom (under normal temperature 1 electron is removed as I am aware) we will receive solid plasma, right? Or if we do the same with Mercury (however removing 80 electrons would be much more difficult compare to Lithium) we will receive liquid plasma, right? :oldeyes:
  2. jcsd
  3. Oct 27, 2018 #2


    User Avatar
    Science Advisor

    The crystal lattice exists, because there are electrons on those shells. The moment you strip the Lithium atoms of all electrons, the nuclei start repelling each other with full might of their three protons, and the lattice breaks down.
    Asking for a solid plasma is like asking for a solid gas. If it's a solid, it's no longer a gas, no?
  4. Oct 27, 2018 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    2018 Award

    If you ionize a gas, then it is no longer a gas. It is now a plasma. It's not a gas that has been ionized in the sense that it is still a gas with just some different properties. It is an entirely different state of matter. It's like saying gas is just a liquid that has evaporated. It's true that a liquid evaporates to become a gas, but gases and liquids are different states of matter for a reason, just like gases and plasma.

    The main difference between plasma and gases is that plasma interacts strongly with electric and magnetic fields, while a gas does not. This leads to drastically different behavior in many situations, which is why we separate plasma from gases.

    No, the entire lattice falls apart and you end up with a plasma. The substance is no longer capable of maintaining its shape, which is one of the defining properties of a solid.

    Again, no. Removing the electrons turns the liquid into a plasma. It gains the properties that all plasmas share and loses the weak inter-atomic/inter-molecular bonds that liquids possess.
  5. Oct 28, 2018 #4
    This has already been stated in simpler form, but...

    Gas is gas

    Liquid is liquid

    Solid is solid

    Plasma is plasma

    These states can't be mixed, matter can only be in one form at a time, it can't be a combination of two or more forms.

    Although, matter in a certain state can "appear" to be in one of the other states or acting "as if" it is in another state, due to external forces or energies(even though it isn't) as long as the force or energy is maintained, such as a liquid under extreme pressures is "solid-like" or a gas that has been compressed to the point that the molecules are so close together that the volume acts "as if" it were a liquid, also known as supercritical fluids(but, I guess that could be argued that the state actually changes, instead of "appears" to change)
  6. Oct 28, 2018 #5

    Mister T

    User Avatar
    Science Advisor
    Gold Member

    A solid is a collection of atoms, so in your scenario you'd have to remove the electrons from a collection of lithium atoms. Temperature is not a property of a single atom, it's a property of collections of them. This collection of lithium ions has a high temperature if all of its electrons are missing. Moreover, without electrons there is no way for that collection to form a solid. Inter-atomic bonds are responsible for solidity, and electrons form those bonds.
  7. Oct 28, 2018 #6
    Is there a clearly defined phase boundary between gas and plasma?
  8. Oct 28, 2018 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    2018 Award

    Not as far as I know.
  9. Oct 28, 2018 #8


    User Avatar
    Science Advisor
    Gold Member

    There are certainly condensed matter plasmas (solid/liquid metals; semiconductors; etc), which is probably what you are interested in. An example book covering some of the physics is Statistical Plasma Physics volume 2 by Ichimaru:


    You should be able to read the first few pages on amazon, which provides an overview of the subject and some examples. I don't really know this book (or condensed matter plasma physics, for that matter) so would never recommend it; I just knew it existed because I had to use volume 1 for a class I took. I wouldn't recommend volume 1 either, by the way.

  10. Oct 28, 2018 #9


    User Avatar
    Staff Emeritus
    Science Advisor
    2018 Award

    How are they defining 'plasma' in condensed matter physics? I couldn't seem to find a definition using google. From the little I've read on the subject these plasmas are not plasmas in the sense they are another phase of matter, they are plasmas in the sense that inside a solid/liquid you can sometimes treat the electrons as an electrically conductive fluid.
  11. Oct 29, 2018 #10

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor

    Sort of- dusty plasmas:

  12. Oct 29, 2018 #11
    According to the book quoted by @jasonRF: "Plasmas are any statistical systems containing mobile charged particles".
    (vol II, section 1.1) According to this definition metals and semiconductors are plasmas.
    This is again a matter of accepted definition rather than some actual physics. I think that a book on plasma may be considered sort of "accepted definition".

    You don't need to go to some exotic states to realize that the boundaries between "states" are not so rigid. There are "solids" that have some properties of liquids, like glasses and amorphous solids, "liquids" that may show properties usually associated with solids and of course, there are liquid crystals. So the nature is more imaginative than just "solid, liquid and gas".
  13. Oct 29, 2018 #12
    How do you decide when the gas stops beeing a gas and turns into plasma without such a phase boundary? In contrast to the transition between solid and liquid or liquid and gas there is no phase transtion between gas and plasma. There is a continous increase of the degree of ionisation with rising temperature but not the sudden change of physical properties that characterises a phase transition. A classification of plasma as a state of matter is therefore at least questionable. It makes sense to refer to gas as a plasma if the ionisation is relevant. But that doesn't mean that it is not a gas anymore.
  14. Oct 29, 2018 #13


    User Avatar

    Staff: Mentor

    Amorphous (non crystalline) solids do not have well defined melting points either, so this isn't unique to plasma.
  15. Oct 29, 2018 #14


    User Avatar
    Staff Emeritus
    Science Advisor
    2018 Award

    I believe they call this a second order phase transition, whereas melting and evaporation are both first order phase transitions.

    Okay. Then you go around and tell all the scientists that they're all wrong and plasma shouldn't be another phase of matter. Or you can make an effort to actually look into the subject a bit and figure out why it's classified as a separate phase instead of just being classified as an ionized gas.
  16. Oct 30, 2018 #15
    Do you have any source describing the gas-plasma phase transition (or even mentioning it)?

    The plasma as the 4-th (or n-th) state of the matter is more likely a pop-science product.
    If there really is a real phase transition between gas and plasma, then plasma should be another phase rather than another state. Similar to solids having several crystalline phases while they are still in the solid state.
  17. Oct 30, 2018 #16
    This is to see if I'm understanding other things that have been mentioned in this thread....

    Differences in crystalline phases of solids are caused by the arrangement of atoms/molecules being different, but the atoms/molecules are still bonded in the traditional manner. Plasma atoms are ionized and lack electrons to form bonds, changing the arrangement of atoms and molecules or even density in the plasma doesn't really change anything about it's state or phase does it?

    That's a question, not a statement.
  18. Oct 30, 2018 #17


    User Avatar
    Staff Emeritus
    Science Advisor
    2018 Award

    About the gas-plasma phase transition:

    Any textbook on plasma physics should have a detailed analysis of this phase transition.

    References to plasma as a state of matter:

    Introduction to Plasma Physics, page 1.

    There is also a phase transition between solid and liquid form, liquid and gas, and other state transitions. Just because it's not named 'state transition' doesn't mean that it doesn't result in a change in the state of the matter. 'Phase' and 'state' are used quite interchangeably in many places, so it's not surprising that there is some confusion.
  19. Oct 30, 2018 #18


    User Avatar
    Staff Emeritus
    Science Advisor
    2018 Award

    I'd like to say that no, it doesn't, but there may be some subtleties about plasmas that I don't understand.
  20. Oct 30, 2018 #19
    Yeah, I hoped you have a paper or a book as a reference. I should have specified this.

    I looked in at least 4 books on plasma physics and the "phase transition" is not even mentioned.
    I hoped you have knowledge about some serious reference about this. It was not a challenging you, I just hoped you have some source that discuss explicitly this problem.

    Phase transition have a specific meaning in the thermodynamics of phase transitions. "State" is more like a common language term and is not equivalent to "phase". Solid state physics studies a lot of different phases that are all, well, solid state.

    Not every change in properties qualifies as a phase transition. And a second order phase transition is sometime called continuous but this means that the first derivative of the free energy is continuous at the transition and only the second derivative is discontinuous. It still have a specific transition temperature (like the Curie temperature for ferromagnetic-paramagnetic phase transition in solid state).
    If you heat up hydrogen gas, at what temperature the gas becomes plasma? Are the transition temperatures listed in plasma textbooks? Isn't the ionization of plasma more like the change in the viscosity of a glassy or waxy material?
  21. Oct 30, 2018 #20
    Well, in a gas the atoms are not bonded either. Or not significantly. But I am not sure I understand your question. What is the "traditional" manner of bonding? There are several different ways of bonding atoms in crystals, in terms of the bonding forces. Are these all "traditional"?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?