Timeline for Is combustion a phase transition?
Current License: CC BY-SA 4.0
20 events
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| Nov 11, 2021 at 14:33 | comment | added | Alchimista | I actually meant that the kinetics and the thermodynamics are treated separated, not that thermodynamics is less important. I was trying to find a criterion. For instance the common example of transition I know are reversible. But I am not sure if it suffice. And finally, the topochemical polymerisation (I worked with) is certainly a reaction as well as a phase transition, it might lack a distinct discontinuity point but I am not sure. Thermally it started just below the monomer mp, but hard to tell if the behavior was due to kinetics or a transition point. | |
| Nov 11, 2021 at 13:54 | comment | added | Roger V. | @Alchimista thank you for giving it a thought - your comment touches all the points that came to my mind. Chemistry indeed focuses on the kinetics (how the transition happens), which is not the focus of equilibrium thermodynamics. Non-equilibrium phase transitions - like which path the reaction chooses - are perhaps of interest to chemists, but not the point here | |
| Nov 11, 2021 at 13:33 | comment | added | Alchimista | ... classical way. It seems an interesting discussion unless I forgot/don't see at the moment a trivial point that would answer your question. However, I would like to mention en.m.wikipedia.org/wiki/Topochemical_polymerization that seems an example in which reaction and a classical intended phase transition are one and the same. Again one cannot return to the monomer, though, if this has importance. Also worth trying at Chemistry SE. | |
| Nov 11, 2021 at 13:28 | comment | added | Alchimista | I am a chemist and this made me realise that I don't know exactly what is the difference between a transition and a reaction if I neglect the high school level definition that we all know. The poon is that thermodynamics as I know put time under the carpet. The energy barrier you wrote about is what determine kinetics. But then even transitions as traditionally intended have they own kinetics. Also the reversibility issue might be or not a issue. Certainly you can go back and forward with a combustion reaction, controlled or not. So I don't see benefit from treatment other than the classical | |
| Nov 11, 2021 at 4:24 | answer | added | bbrink | timeline score: 1 | |
| Nov 10, 2021 at 17:24 | comment | added | Roger V. | @SolomonSlow Please take no offense as well. | |
| Nov 10, 2021 at 17:00 | comment | added | Solomon Slow | @RogerVadim, I'm just saying, it's a term of art. It saves time and mental energy every time someone uses it in conversation. There's a lot of newbies here, and then there's some people here who know real physics but, who don't have the patience to deal with "dumb" questions. I try to help noobs ask questions that won't get dumped on. If someone spends time and energy describing what could have been said with a word or two, that can be a clue. Sometimes, I misjudge, or I fail to thoroughly read what they wrote. I hope I did not offend. | |
| Nov 10, 2021 at 16:36 | comment | added | Roger V. | @EdV Good idea. Phase transition and thermodynamics seem very much physics to me... besides this is my native language. But surely chemists might know about it quite a bit. | |
| Nov 10, 2021 at 16:21 | comment | added | Ed V | Thanks for the opportunity, but why not ask it over at chemistry SE? We have some folks there who can answer much better than I can. | |
| Nov 10, 2021 at 16:12 | comment | added | Roger V. | @EdV You might be right: if you can clearly explain why it is not a phase transition, please write an answer. | |
| Nov 10, 2021 at 16:03 | comment | added | Ed V | I am a chemist, I have detonated hydrogen and oxygen mixtures (without injury) and, quite frankly, there is no way it is a phase change. As well, evaporation is not a chain reaction. Activation energies for chemical reactions are of great importance in chemistry, along with the associated kinetics and thermodynamics, but chemical reactions are not all phase changes, no matter how broadly that may be defined. | |
| Nov 10, 2021 at 15:47 | comment | added | Roger V. | @SolomonSlow Activation energy is discussed at length in my question (although I didn't use exactly this term anywhere - it was understood that it is clear). | |
| Nov 10, 2021 at 15:27 | answer | added | akhmeteli | timeline score: 2 | |
| Nov 10, 2021 at 15:26 | comment | added | Solomon Slow | Re, "...they convert with explosion to water," "Explosion" is a physical descriptionāsomething disintigrates and the pieces of it fly off in different directions. The name of the chemical process that could cause a container filled with hydrogen and oxygen to explode is detonation. | |
| Nov 10, 2021 at 15:23 | comment | added | Solomon Slow | Re, "š»2 and š2 may remain a gaseous mixture for a very long time, unless we heat it or..." Read about activation energy. | |
| Nov 10, 2021 at 15:09 | comment | added | Roger V. | @DavidWhite that's because it is first order - one minima in Landau free energy is lower. | |
| Nov 10, 2021 at 15:08 | comment | added | Roger V. | @EdV I don't think that the two viewpoints are mutially exclusive: one can discuss the kinetics of phase transitions, like evaporation/condensation, melting/crystallization or remagnetization via formation of domains - all of them can be viewed as chain reactions. | |
| Nov 10, 2021 at 15:07 | comment | added | David White | I agree with Ed V. You can't take hot combustion products (e.g., water vapor), cool them down, and end up with the starting reactants. | |
| Nov 10, 2021 at 15:02 | comment | added | Ed V | Combustion is not a phase transition! Think more like a chain reaction involving free radicals. Burning hydrogen gas in oxygen gas results in water vapor. | |
| Nov 10, 2021 at 14:55 | history | asked | Roger V. | CC BY-SA 4.0 |