Phase equilibrium - beyond critical point

In summary: I would like to see more definitions on this, as I am not entirely clear on what you mean by "thermodynamic state".
  • #1
KLscilevothma
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phase equilibrium -- beyond critical point

In a phase diagram, at critical point, liquid phase is indistinguishable from vapour, and beyond which, only vapour can be found. Matter has four states, liquid, solid, gas and plasma. Can we include plasma state in a phase diagram? If yes, how should the phase diagram be drawn? Also, I'm not very clear of what plasma state is, could someone give me a URL/explanation on that please.
 
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  • #2


Originally posted by KL Kam
In a phase diagram, at critical point, liquid phase is indistinguishable from vapour, and beyond which, only vapour can be found. Matter has four states, liquid, solid, gas and plasma. Can we include plasma state in a phase diagram? If yes, how should the phase diagram be drawn? Also, I'm not very clear of what plasma state is, could someone give me a URL/explanation on that please.

A plasma is just an ionized gas. I don't think phase transitions apply here since this is not a thermodynamic state, ie. we don't arrive at this state through a thermodynamic process...less the fact that we need a gas. Ionization can only be explained through QM.

How's the studying coming along?
 
  • #3


Originally posted by Ivan Seeking
I don't think phase transitions apply here since this is not a thermodynamic state, ie. we don't arrive at this state through a thermodynamic process...less the fact that we need a gas. Ionization can only be explained through QM.

How's the studying coming along?
An elememtary question, what is a thermodynamic state? I know if we apply lots of energy to matter, say sodium, it will change from solid state to liquid state, then to vapour state, and then turn into plasma, but I don't understand the term "thermodynamic state".

The last exam paper that requires me to study beforehand will be finished in 5 hours.
 
  • #4


Originally posted by KL Kam
I know if we apply lots of energy to matter, say sodium, it will change from solid state to liquid state, then to vapour state, and then turn into plasma..

Hmmmm. True. I guess this gets to be risky business since it all come down to QM eventually. I guess what I meant was a state that can be described by the principles of thermodynamics - statistical calculations and such. I think the problem is that Classical Thermodynamics cannot address the formation of plasma. But you are correct that it is just another state dependent on the energy in the system. By this, I think that we could argue that fusion is a phase transition also. So, perhaps you touch on Quantum Thermodynamics with this question? I also think your point is valid. These do seem like other phase transitions. This could also be a simple matter of definition; the ones that we use fail to address your suggestion.
 

What is phase equilibrium?

Phase equilibrium refers to the state where two or more phases of a substance coexist in equilibrium with each other. This means that the substance is in a state where the amount of each phase does not change over time.

What is the critical point of a substance?

The critical point of a substance is the temperature and pressure at which the liquid and gas phases of the substance become indistinguishable from each other. At this point, the substance is in a supercritical state and exhibits unique properties.

What happens to a substance beyond its critical point?

Beyond the critical point, a substance no longer exists in distinct liquid and gas phases. It becomes a supercritical fluid, with properties that are in between those of a liquid and a gas. It also exhibits unique properties, such as increased solubility and diffusion.

How is phase equilibrium beyond the critical point different from that at lower pressures?

At lower pressures, phase equilibrium occurs between distinct liquid and gas phases. However, beyond the critical point, the substance exists as a single phase and the concept of phase equilibrium no longer applies. Instead, the substance reaches a state of thermodynamic equilibrium.

What are the applications of studying phase equilibrium beyond the critical point?

Studying phase equilibrium beyond the critical point has many practical applications, such as in the development of supercritical fluid extraction techniques, synthesis of nanoparticles, and in the chemical and pharmaceutical industries. It also has potential uses in energy production and storage.

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