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Here and in the 'list of Phases of matter' article there is confusion between the usage of 'phase' to denote the difference of liquid vs. solid as opposed to the the difference between diamond and graphite. The liquid vs. solid distinction is properly a difference in 'state of matter' -- yes they are necessarily different phases, too. However, in the diamond vs. graphite case, both ate the same state of matter (solid) but different phases.
There is much in the first two paragraphs which do not belong in an article on phases, but which should instead be part of an article on 'states of matter'. Although there may be some contexts where 'phase' and 'state of matter' may be used interchangeably, it only adds to the confusion here.
I propose that the solid/liquid/gas/Bose-Einstein condensate part of this article be removed to another article dealing with states of matter, and this article focus on the other meaning (diamond vs. graphite, fcc-iron vs. bcc-iron, liquid miscibility issues like oil/water, etc.) Olof
So I've gone and done the disambiguation between state of matter and phase. I believe a number of other articles now are more coherent, and a number of links make more sense.. However, there are plenty of loose ends to do -- and I'm not really sure what to do with the states of matter template -- Olof ( talk • contribs) 10:01, 11 January 2007 (UTC).
Some careful rewriting is certainly necessary, but note that there is a real distinction between a 2-phase system and a 2-state system. For example an oil-water system has 2 phases (for certain compositions) but only one (liquid) state. Dirac66 ( talk) 01:42, 9 November 2008 (UTC)
Hi there. I was reading this article, and found myself amazed with those two sentences which seem contradictory to me :
So my question is : How can we have a phase as as set of states when two states have necessarily two different phases ?
Does the first sentence may in fact be "a state is a set of phases" (which is not as correct as "a system can have multiple phases which are in equilibrium with each other and also in the same state of matter" -I think the best "all-in-one" of this article)
Am I missing something or is my comment right ? -- JcDenaes
Thank you a lot ! I understand now. -- JcDenaes
There are several misconceptions of phases, and specifically phase transitions in this article. Mostly, it completely ignores second-order phase transitions, in which the free energy function stays differentiable, even at the transition. This also means, that the latent heat (energy related to the change in phase) is zero at the critical value. A perfect example of this is mentioned just above here: the superconducting phase transition. At some critical temperature (or critical magnetic field strength, but this is a bit touchy, as some energy is related to displacing the magnetic field around the superconductor), metallic superconductors become superconducting, which, as mentioned, is a different phase of matter. However, no energy is released in the process, nor is any taken up. This is in clear contradiction to a number of statements in the "General definition..." section. The page on phase transitions has a much clearer description, which should be linked to in stead. 195.215.65.50 ( talk) 21:59, 28 November 2007 (UTC)
Further to a discussion above, I undertook a significant rewrite.
The definition of a phase as a "set of states" is now gone. The definition seems to be based on looking at phase diagrams and is not commensurate with the definition in my references, which I know is widely used. The "set of states" definition works poorly when you watch what happens to liquid and gas phases around and "above" the critical point.
I also took out the definition of phase boundaries in terms of the free-energy becoming "non-analytic" That definition seems to derive from experiments where you observe sudden changes in things such as heat capacity as your system moves from a single phase into a two phase region (or back the other way). This type of behavior gets treated in a different guise by the new version. Non-analytic seems to be meant with reference to the phase diagram (derivatives with respect to pressure and temperature), not with respect to space (derivatives with respect to spatial coordinates). Again, the definition based on phase diagrams and phase experiments is certainly not universal. I also wonder whether it is practical outside the study of phase diagrams.
Another problem with the old description and definition is that it was of little or no practical use to anyone who might consult this page. I know I did not understand it the first few time I read it in spite of my have background in this area.
The description under "phase separation" also received the axe. The removed material referred to a mathematical model of fluid movement in a dynamic process of phase separation. It was not a model describing when phase separations would occur. It was distracting, meaningless, and useless to nearly anyone who might consult this page. Also, the content was only remotely related to the main topic.
I removed material about solubility, which is a different topic.
If you are looking for a description of the exemplary system having eight immiscible liquid phases, check the footnotes. My reason for removing most of that description was that it did not add enough to the discussion to deserve the space it was taking. Paul V. Keller ( talk) 17:17, 25 November 2008 (UTC)
I agree that the rewritten article is at a better level for most readers including chemistry students, and that much of the deleted material was overly mathematical for this article.
I think the next step is to add references to appropriate sections of some standard physical chemistry books, for example Atkins and de Paula. Dirac66 ( talk) 23:12, 25 November 2008 (UTC)
First, I realized that the reference which you did add (Modell and Reid) did not appear in the article because your rewrite accidentally omitted the ==References== section with the source code which makes references appear. I have now fixed this.
As for distinct phases vs. distinct states: The enumeration of phases is clear because a phase is well defined as a region with uniform properties. So ice I and ice III are two distinct phases because their density is different, as are normal aluminum and superconducting aluminum because their conductivity is different (one finite, one infinite). Counting phases this way is necessary to satisfy the phase rule: ice I and ice III are in equilibrium on a curve (1 degree of freedom) just like ice I and water, so F=C-P+2 requires that P=2.
The word "states" has several different meanings, as we have already discussed at Talk: State of matter#States of matter vs. Thermodynamic state. The "set of states" definition refers to "thermodynamic states", e.g. ice I at -10oC and 1 atm, ice I at -9.9oC and 1 atm, etc. These refer to one and the same phase whose properties vary slowly. If you want to put this definition back in the article, then "thermodynamic states" would be much clearer.
As for different "crystal states" such as ice I and ice III, their enumeration is variable depending on the author and often the context for the same author. Sometimes "state (of matter)" is used as a synonym for "phase", and other times phrases such as "solid state" imply that ice I and ice III are in the same state. Similarly for normal and superconducting phases of a metal. This is a confusing and unfortunate situation, but Wikipedia cannot impose precision upon the scientific world. Best I think to use "phase" (and perhaps "thermodynamic state") in this article, and keep "states of matter" in the other article without a precise enumeration. Dirac66 ( talk) 03:32, 30 November 2008 (UTC)
(continues previous section: Fall 2008 re-write)
In chemistry the recognized authority for definition of terms is IUPAC, at least for the limited number of terms they consider. The IUPAC Gold Book defines "Phase" as "An entity of a material system which is uniform in chemical composition and physical state." [1] This is similar to what we have now, and I think we should use the words of IUPAC as the initial definition to start the article, with a link to the Gold Book.
IUPAC does not refer to a set of states, but we could add a remark after the definition. Perhaps something like "For systems in equilibrium, a phase may be considered as a set (or range) of thermodynamic states whose properties vary continuously." Yes, I did forget about non-equilibrium states until reading your last edit; if we follow IUPAC and do not present this remark as a general definition, then we can just exclude them with the initial phrase "For systems in equilibrium".
Unfortunately the Gold Book does not help with state of matter, which is not among the 6852 terms it defines. Dirac66 ( talk) 01:30, 1 December 2008 (UTC)
Well, the Modell-Reid definition is certainly clearer, and close enough to the official IUPAC version so that I think it is acceptable. I agree that "entity" is certainly a confusing word, and "region" is much clearer. The important point is that the basic definition should contain the idea of a uniform subsystem (entity or region in physical space), rather than the idea of a set of states (in parameter space) which is more complicated and also only applies to equilibrium systems. Dirac66 ( talk) 04:09, 1 December 2008 (UTC)
According to [2] doi: 10.1126/science.1227224 there should be more than 500+ phases -- 70.24.247.127 ( talk) 01:27, 25 December 2012 (UTC)
Yes, there are more than 500+ phases. In fact, the Inorganic Crystal Structure Database has 161,030 entries, each of which represent a phase (although some might not have a phase boundary between them). As the authors of the Science paper state in their abstratc, by symmetry arguments alone, there are 230 possible different crystal structures, each of which would need to be its own phase. More phases are indeed possible when one considers additional degrees of freedom. Are you asking us to clarify the number of topologically distinct phases possible in general? Mgibby5 ( talk) 14:44, 5 February 2015 (UTC)
I would like to have all known phases of matter listed somewhere, either in the form of a bullet list or as a table. Currently, you just have to read the text in hope of finding them all implicitly listed somewhere, although they are not. Could anyone who know which all these phases are please make a list of them? — Kri ( talk) 21:03, 21 July 2014 (UTC)
It is fairly inconvenient to list all possible, distinct phases: each different crystal structure is a different phase, by symmetry arguments. Further, several different phases can exist in equilibrium with each other, but each have the same crystal structure, just as liquids can exist in equilibrium with one another (oil and water are separate phases, despite possessing the same symmetries). It is not useful in practice to provide a list of all possible phases. Mgibby5 ( talk) 14:37, 5 February 2015 (UTC)
Can we have a section on the history of the discovery of phase structures, please? — Preceding unsigned comment added by 176.252.227.106 ( talk) 13:08, 25 January 2015 (UTC)
In the last paragraph under number of phases is the following: "By charging the right amount of water and applying heat, the system can be brought to any point in the gas region of the phase diagram. "
1) The syntax of charging the right amount of water seems a bit clunky and probably refers to a specific experimental apparatus? I interpret it to mean controlling the amount (mols I assume - but that is problematic because we don't have a vloume) of water in the described system.
2) Going from the amounts issue above: the relative amounts of material in a system is a variable that can affect phase but is not what is represented in the attendant 2D phase diagrams (only T & P are). It is probably best to avoid adding compositional axes too for this discussion.
Suggestion: Could we edit this to say something like "By controlling the temperature (degrees K) and the magnitude of pressure (here shown in MPa) the system can be brought to any point on the phase diagram. From a point in the solid stability region (left side of diagram) increasing the temperature of the system would bring it into the region where a liquid or a gas is the equilibrium phase (depending on the pressure).
By CrispGeochem — Preceding unsigned comment added by 151.213.119.209 ( talk) 16:27, 1 May 2020 (UTC)
![]() | This ![]() It is of interest to the following WikiProjects: | |||||||||||||||||
|
Archives: 1 |
|
Here and in the 'list of Phases of matter' article there is confusion between the usage of 'phase' to denote the difference of liquid vs. solid as opposed to the the difference between diamond and graphite. The liquid vs. solid distinction is properly a difference in 'state of matter' -- yes they are necessarily different phases, too. However, in the diamond vs. graphite case, both ate the same state of matter (solid) but different phases.
There is much in the first two paragraphs which do not belong in an article on phases, but which should instead be part of an article on 'states of matter'. Although there may be some contexts where 'phase' and 'state of matter' may be used interchangeably, it only adds to the confusion here.
I propose that the solid/liquid/gas/Bose-Einstein condensate part of this article be removed to another article dealing with states of matter, and this article focus on the other meaning (diamond vs. graphite, fcc-iron vs. bcc-iron, liquid miscibility issues like oil/water, etc.) Olof
So I've gone and done the disambiguation between state of matter and phase. I believe a number of other articles now are more coherent, and a number of links make more sense.. However, there are plenty of loose ends to do -- and I'm not really sure what to do with the states of matter template -- Olof ( talk • contribs) 10:01, 11 January 2007 (UTC).
Some careful rewriting is certainly necessary, but note that there is a real distinction between a 2-phase system and a 2-state system. For example an oil-water system has 2 phases (for certain compositions) but only one (liquid) state. Dirac66 ( talk) 01:42, 9 November 2008 (UTC)
Hi there. I was reading this article, and found myself amazed with those two sentences which seem contradictory to me :
So my question is : How can we have a phase as as set of states when two states have necessarily two different phases ?
Does the first sentence may in fact be "a state is a set of phases" (which is not as correct as "a system can have multiple phases which are in equilibrium with each other and also in the same state of matter" -I think the best "all-in-one" of this article)
Am I missing something or is my comment right ? -- JcDenaes
Thank you a lot ! I understand now. -- JcDenaes
There are several misconceptions of phases, and specifically phase transitions in this article. Mostly, it completely ignores second-order phase transitions, in which the free energy function stays differentiable, even at the transition. This also means, that the latent heat (energy related to the change in phase) is zero at the critical value. A perfect example of this is mentioned just above here: the superconducting phase transition. At some critical temperature (or critical magnetic field strength, but this is a bit touchy, as some energy is related to displacing the magnetic field around the superconductor), metallic superconductors become superconducting, which, as mentioned, is a different phase of matter. However, no energy is released in the process, nor is any taken up. This is in clear contradiction to a number of statements in the "General definition..." section. The page on phase transitions has a much clearer description, which should be linked to in stead. 195.215.65.50 ( talk) 21:59, 28 November 2007 (UTC)
Further to a discussion above, I undertook a significant rewrite.
The definition of a phase as a "set of states" is now gone. The definition seems to be based on looking at phase diagrams and is not commensurate with the definition in my references, which I know is widely used. The "set of states" definition works poorly when you watch what happens to liquid and gas phases around and "above" the critical point.
I also took out the definition of phase boundaries in terms of the free-energy becoming "non-analytic" That definition seems to derive from experiments where you observe sudden changes in things such as heat capacity as your system moves from a single phase into a two phase region (or back the other way). This type of behavior gets treated in a different guise by the new version. Non-analytic seems to be meant with reference to the phase diagram (derivatives with respect to pressure and temperature), not with respect to space (derivatives with respect to spatial coordinates). Again, the definition based on phase diagrams and phase experiments is certainly not universal. I also wonder whether it is practical outside the study of phase diagrams.
Another problem with the old description and definition is that it was of little or no practical use to anyone who might consult this page. I know I did not understand it the first few time I read it in spite of my have background in this area.
The description under "phase separation" also received the axe. The removed material referred to a mathematical model of fluid movement in a dynamic process of phase separation. It was not a model describing when phase separations would occur. It was distracting, meaningless, and useless to nearly anyone who might consult this page. Also, the content was only remotely related to the main topic.
I removed material about solubility, which is a different topic.
If you are looking for a description of the exemplary system having eight immiscible liquid phases, check the footnotes. My reason for removing most of that description was that it did not add enough to the discussion to deserve the space it was taking. Paul V. Keller ( talk) 17:17, 25 November 2008 (UTC)
I agree that the rewritten article is at a better level for most readers including chemistry students, and that much of the deleted material was overly mathematical for this article.
I think the next step is to add references to appropriate sections of some standard physical chemistry books, for example Atkins and de Paula. Dirac66 ( talk) 23:12, 25 November 2008 (UTC)
First, I realized that the reference which you did add (Modell and Reid) did not appear in the article because your rewrite accidentally omitted the ==References== section with the source code which makes references appear. I have now fixed this.
As for distinct phases vs. distinct states: The enumeration of phases is clear because a phase is well defined as a region with uniform properties. So ice I and ice III are two distinct phases because their density is different, as are normal aluminum and superconducting aluminum because their conductivity is different (one finite, one infinite). Counting phases this way is necessary to satisfy the phase rule: ice I and ice III are in equilibrium on a curve (1 degree of freedom) just like ice I and water, so F=C-P+2 requires that P=2.
The word "states" has several different meanings, as we have already discussed at Talk: State of matter#States of matter vs. Thermodynamic state. The "set of states" definition refers to "thermodynamic states", e.g. ice I at -10oC and 1 atm, ice I at -9.9oC and 1 atm, etc. These refer to one and the same phase whose properties vary slowly. If you want to put this definition back in the article, then "thermodynamic states" would be much clearer.
As for different "crystal states" such as ice I and ice III, their enumeration is variable depending on the author and often the context for the same author. Sometimes "state (of matter)" is used as a synonym for "phase", and other times phrases such as "solid state" imply that ice I and ice III are in the same state. Similarly for normal and superconducting phases of a metal. This is a confusing and unfortunate situation, but Wikipedia cannot impose precision upon the scientific world. Best I think to use "phase" (and perhaps "thermodynamic state") in this article, and keep "states of matter" in the other article without a precise enumeration. Dirac66 ( talk) 03:32, 30 November 2008 (UTC)
(continues previous section: Fall 2008 re-write)
In chemistry the recognized authority for definition of terms is IUPAC, at least for the limited number of terms they consider. The IUPAC Gold Book defines "Phase" as "An entity of a material system which is uniform in chemical composition and physical state." [1] This is similar to what we have now, and I think we should use the words of IUPAC as the initial definition to start the article, with a link to the Gold Book.
IUPAC does not refer to a set of states, but we could add a remark after the definition. Perhaps something like "For systems in equilibrium, a phase may be considered as a set (or range) of thermodynamic states whose properties vary continuously." Yes, I did forget about non-equilibrium states until reading your last edit; if we follow IUPAC and do not present this remark as a general definition, then we can just exclude them with the initial phrase "For systems in equilibrium".
Unfortunately the Gold Book does not help with state of matter, which is not among the 6852 terms it defines. Dirac66 ( talk) 01:30, 1 December 2008 (UTC)
Well, the Modell-Reid definition is certainly clearer, and close enough to the official IUPAC version so that I think it is acceptable. I agree that "entity" is certainly a confusing word, and "region" is much clearer. The important point is that the basic definition should contain the idea of a uniform subsystem (entity or region in physical space), rather than the idea of a set of states (in parameter space) which is more complicated and also only applies to equilibrium systems. Dirac66 ( talk) 04:09, 1 December 2008 (UTC)
According to [2] doi: 10.1126/science.1227224 there should be more than 500+ phases -- 70.24.247.127 ( talk) 01:27, 25 December 2012 (UTC)
Yes, there are more than 500+ phases. In fact, the Inorganic Crystal Structure Database has 161,030 entries, each of which represent a phase (although some might not have a phase boundary between them). As the authors of the Science paper state in their abstratc, by symmetry arguments alone, there are 230 possible different crystal structures, each of which would need to be its own phase. More phases are indeed possible when one considers additional degrees of freedom. Are you asking us to clarify the number of topologically distinct phases possible in general? Mgibby5 ( talk) 14:44, 5 February 2015 (UTC)
I would like to have all known phases of matter listed somewhere, either in the form of a bullet list or as a table. Currently, you just have to read the text in hope of finding them all implicitly listed somewhere, although they are not. Could anyone who know which all these phases are please make a list of them? — Kri ( talk) 21:03, 21 July 2014 (UTC)
It is fairly inconvenient to list all possible, distinct phases: each different crystal structure is a different phase, by symmetry arguments. Further, several different phases can exist in equilibrium with each other, but each have the same crystal structure, just as liquids can exist in equilibrium with one another (oil and water are separate phases, despite possessing the same symmetries). It is not useful in practice to provide a list of all possible phases. Mgibby5 ( talk) 14:37, 5 February 2015 (UTC)
Can we have a section on the history of the discovery of phase structures, please? — Preceding unsigned comment added by 176.252.227.106 ( talk) 13:08, 25 January 2015 (UTC)
In the last paragraph under number of phases is the following: "By charging the right amount of water and applying heat, the system can be brought to any point in the gas region of the phase diagram. "
1) The syntax of charging the right amount of water seems a bit clunky and probably refers to a specific experimental apparatus? I interpret it to mean controlling the amount (mols I assume - but that is problematic because we don't have a vloume) of water in the described system.
2) Going from the amounts issue above: the relative amounts of material in a system is a variable that can affect phase but is not what is represented in the attendant 2D phase diagrams (only T & P are). It is probably best to avoid adding compositional axes too for this discussion.
Suggestion: Could we edit this to say something like "By controlling the temperature (degrees K) and the magnitude of pressure (here shown in MPa) the system can be brought to any point on the phase diagram. From a point in the solid stability region (left side of diagram) increasing the temperature of the system would bring it into the region where a liquid or a gas is the equilibrium phase (depending on the pressure).
By CrispGeochem — Preceding unsigned comment added by 151.213.119.209 ( talk) 16:27, 1 May 2020 (UTC)