# What is Phase transitions: Definition and 50 Discussions

In chemistry, thermodynamics, and many other related fields, phase transitions (or phase changes) are the physical processes of transition between the basic states of matter: solid, liquid, and gas, as well as plasma in rare cases.
A phase of a thermodynamic system and the states of matter have uniform physical properties. During a phase transition of a given medium, certain properties of the medium change, often discontinuously, as a result of the change of external conditions, such as temperature, pressure, or others. For example, a liquid may become gas upon heating to the boiling point, resulting in an abrupt change in volume. The measurement of the external conditions at which the transformation occurs is termed the phase transition. Phase transitions commonly occur in nature and are used today in many technologies.

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1. ### I Topological phase transitions for the whole Universe...?

Physicist Grigory Volovik has put forward some ideas about the universe undergoing a topological phase transition (especially in the early stages of the universe). He published a book called "*The Universe in a Helium Droplet*" where he explained his ideas. You can find a brief discussion here...
2. ### Phase Transitions in the Van Der Waals Gas

Hi, I am not quite sure if I have understood the second task correctly, but I proceeded as follows. It's about what happens to the isothermal compressibility when the free energy becomes minimal. In the first task there was already the equation ##\kappa_T=\frac{1}{V}\Bigl( \frac{\partial^2...
3. ### A What Are Examples of Exotic Order-Disorder Phase Transitions?

I am looking for possible examples and a variant of Landau's theory of phase transitions for an exotic order-disorder phase transition, in which a thermodynamic system jumps into a disordered (or less orderly) state by reaching the maximum critical value of the order parameter. That is, in one...
4. ### A Do gas-gas and/or liquid-liquid phase transitions exist?

I'm writing a short report about thermal storage using latent heat and the topic is liquid/solid phase transitions. I would however like to systematize all phase transitions in the intro and I'm curious if gas/gas and/or liquid/liquid phase transitions exist. For gas-gas I think that the...
5. ### A How do soft Pomerons become hard?

The exchange of soft Pomerons (and Reggeons) (##\alpha_R(0)=0.55## and ##\alpha_P(0)=1.08##) seem to describe total hadron-hadron cross sections pretty well in the Regge limit. See, for example: https://arxiv.org/abs/hep-ph/9209205 In this limit, QCD is of very little use since the exchanged...
6. ### A Is the cluster decomposition equivalent to no phase transitions?

I think the cluster decomposition states that products of space like separated observable decouple when sandwiched with states. An analogy with statistical mechanics seems to suggest that we are stating there are no phase transitions. For example, in the Ising model all spins are correlated in...
7. ### A Does the Material Cu2OSeO3 Have a Solid-Liquid Critical Point?

In many phase diagrams of a single substance, there is a triple point, where the solid, liquid and gas phases coexist in equilibrium, and there is a liquid-gas critical point beyond which, the transition between liquid and gas becomes continuous, and the substance is known as a super-critical...
8. ### Phase transitions in a superconductor

Homework Statement The phase transition to a superconducting state moves to lower temperatures as the applied magnetic field, H, increases. The magnetic moment, M, for a system of volume V is given by: $$M=-\frac{HV}{4\pi}$$ for ##H<H_C(T)## (superconducting) and $$M=0$$ ##H>H_C(T)## (normal)...
9. ### A Criticality, phase transitions and closing bandgap

At critical points, when correlation lengths diverge near a phase transition, people often say that the spectral gap closes, which is to my understanding just the energy difference between the ground state and the first excited state (the first two eigenvalues of the hamiltonian). How should we...
10. ### A Meaning of phase transitions in lattice gauge theories

Hi all Decided to post in 'beyond standard model' because lattice gauge theories are usually used to explore these models. Hope that's all right. So in lattice simulations, phase transitions in beta mass plane seem to have an important meaning. I understand phase transitions from a...
11. ### B Electroweak spontaneous symmetry breaking

This is a question that I have tried to pose several times without any success but, anyway, I would like to try again for the very last time. Asume for a moment that EW-SSB (electroweak spontaneous symmetry breaking) actually happened in our early universe. Imagine that our Standard Model of...
12. ### Condition for condensation from adiabatic expansion

Homework Statement I'm stuck on part (c) of this question. Homework Equations $$T\frac{d}{dT}\bigg(\frac{L}{T}\bigg) \equiv \frac{dL}{dT} - \frac{L}{T}.$$ Clausius-Clapeyron equation: $$\frac{dp}{dT} = \frac{L}{T\Delta V} \approx \frac{L}{TV_{vap}}.$$ The Attempt at a Solution My approach...
13. ### I Phase transitions university classes

There's something that I'd like to know and haven't been able to find in any book: 1.- Is the number of second order phase transition university classes known? 2.- Do we know quantitatively know the behavior of all such second order phase transition university classes? 3.- Do we know the...
14. ### How can phase transitions be physical equilibriums?

I have been told that phase transitions=physical equilibriums. How can phase transitions be physical equilibriums? For example, if you have liquid water going into gas phase, doesn't delta G have to be greater than 0 for the phase change to occur? Is physical equilibrium an assumption in phase...
15. ### Why does the temperature is invariant on phase transitions?

Hello there, this is a fact that I can't understand thinking about it... Energy has to be given so that the inter molecular bonds can be broken, and energy goes in when there are formed (even though that sounds very counter intuitive to me), but why is the energy all distributed to potential...
16. ### P28 of phase transitions and the renormalization group

Hi, I'm confused about the discussion on p28 of Nigel Goldenfeld's "Lectures on phase transitions and the renormalization group" (this question can only be answered by people who have access to the book.) The goal is to compute the potential energy of a uniformly charged sphere where the...
17. ### Examples of First-Order *Electronic* Phase Transitions?

Hi, I'm wondering if people could help me compile a list of ELECTRONIC phase transitions, that are FIRST-ORDER, that occur at room temperature and can be driven by things like doping, strain, magnetic fields, etc. rather than temperature. Any suggestions are greatly appreciated. Also, would...
18. ### Do Any Chemicals Undergo Reverse Phase Transitions?

Are there any chemicals that are liquid under high pressure (above 1 atmospheres) but solid when exposed to low pressures (below 1 atmosphere)? Are there any chemicals that have a similar reverse phase transition at any pressure with the solid extending down to vacuum?
19. ### Statistical Mechanics of Phase Transitions

Hello everyone! :) I am studying for an honours course in Statistical Physics. I have stumbled upon the book "Statistical Mechanics of Phase Transitions" by J.M. Yeomans. The layout of the book, as well as information, is exactly what I need. I want to work through the problems and was...
20. ### Where does energy go during phase transitions?

Sorry for such a simple question but where do we model the energy going during phase transitions? If I had a mercury thermometer in a pot of water, and I had a 200 degree Celsius heat reservoir in contact with the water, I would see the water temp hold steady during the phase transition...
21. ### Understanding Freeze-Drying: IR Radiations, Sublimation & Phase Transitions

Well! the material to be freeze-dried is irradiated with IR radiations before, why?? Also I am confused as to how can ice sublime at atmospheric pressure?? Isn't the triple point of water much lower? is the vacuum around the material created for this reason? ( to lower the pressure I mean) Also...
22. ### How to estimate latent heat of polymorphic phase transitions

Hello, I know that the latent heat of a first-order isothermal and isobaric phase transition is in general given by the difference in enthalpies between the two phases, but my question is: do you know if there is there a way to estimate its value "from first principles" for the case of a...
23. ### Question about phase transitions and PV, VT diagrams

Question: A) Explain what happens when a gas is kept in a cylinder under constant pressure while being cooled. Assume that constant pressure is less than critical pressure. Draw PT and VT diagrams for this? B) Describe and explain what is seen when a strong transparent container of constant...
24. ### Dynamics of phase transitions

I'm merely starting to research this field. Phase transitions have always been a mystery for me. Which kinds of dynamics govern when a material will undergo a phase transition? e.g., why is it exactly at the temperature T0 and pressure p0 that the substance X goes from one phase to the other...
25. ### Finite size effects at first order phase transitions

Hi. I am trying to understand some features related to the order of a phase transition. It is known that there are finite size effects in a finite system. The finite size scaling theory provides relations between some quantities with the length of the system L. At second order phase...
26. ### Dimension, fluctuations, and phase transitions

Hey all, I'm reading Chaikin's Principles of Condensed matter, and he's talking about the effect fluctuations have in various systems. He says: So I get why order is destroyed in 1D, and not in 2D. But I don't see why they destroy the phase transitions. Can anyone tell me? Thanks!
27. ### Exploring the Difference between KT and Ferro-Para Phase Transitions

i cannot see the reason what makes KT phase transition different from the ferro-para phase transition of the 2D ising model?

I realized yesterday that I don't know nearly as much as I would like about the physics of phase transitions. How do bubbles form when water boils? How do condensation nuclei work? I had a whole host of questions that I didn't feel adequately able to answer. Can anyone recommend a good...
29. ### Phase Transitions: Why is the pressure constant?

I have a question regarding phase transitions: It all textbook I've seen the assumption that dP=0 during a phase transition (so that for example dH=TdS is true during a phase transition). Could anyone explain why this should be true? I guess I could relate this question to a question I...
30. ### Explain 'bubbles' in cosmological phase transitions

Can someone, please, explain to me (in layman's terms, [ie no mathematics]) the theory behind early cosmological phase transitions and these supposed 'bubbles' ?
31. ### Critical Exponents for Quantum Phase Transitions

Hi All, I'm doing an undergraduate project regarding QPTs for some variation of a AF Heisenberg hamiltonian. I'm a little confused about the change in relations between the critical exponents for a QPT. Some books/papers state that the quantum system in D dimensions is mapped to a classical D +...
32. ### Observing Thermodynamic Phase Transitions Via Neutron Scattering

Hi, before I start this is not coursework or any work attached to my degree but part of an internship at a neutron research facility at a level appropriate for Masters students and higer, so I felt it necessary to post it here rather than the homework section (sorry if I'm mistaken). I've been...
33. ### Phase transitions between solid and liquid. Critical point CP

Look at a simple single - component system. And PT diagram for this system. Suppose that supstance we looking at has three phases solid, liquid and gas. In that case we have critical point between liquid and gas phase, but not between solid and liquid phase. Why? Why solid - liquid coexistence...
34. ### Phase Transitions: Melting from Heat Transfer

Hi, I am revising and I was wondering if it is correct to say: "Imagine we have a solid at a low temperature. If we allow it to interact thermally with a hotter body, energy will be gradually transferred from the hot object to the cold object. The colder object will take in the heat energy...
35. ### Phase Transitions Exist Only In the Thermodynamic Limit Or

It is often said that phase transitions only exist in the thermodynamic limit based on some proof like: -A system has time-reversal symmetry thus its TOTAL free energy F(H)=F(-H) (H is the field) therefore the magnetization is M(H)=\frac{\partial F(H)}{\partial H}=\frac{\partial...
36. ### What's Wrong With Landau's Theory of Phase Transitions

What's "Wrong" With Landau's Theory of Phase Transitions Every book under the sun tells you that the Landau method is wrong because it "fails to consider fluctuations" but I don't see how that's true. It's got a gradient term of the form (\nabla M )^2 and one could then include higher order...
37. ### Calculating Phase Transitions in a Water-Ice Mixture

Homework Statement Ice at 0°C is mixed with 5 x 10^2 mL of H2O at 25°C. How much ice must melt to lower the H2O temp to 0°C? Homework Equations mcΔt = -[mcΔt] The Attempt at a Solution (500ml)(4.186 kJ/kg*K)(-25) = m(2.1 kJ/kg*K)(25) 996 ml or gram equivalents I know this...
38. ### How to Solve an Energy Change Equation Involving Temperature?

Can you please show me the steps on how to solve this equation for change in energy I have tried but I don't get the answer in the back of the book. I am looking for T 7098+(0.02*4186)(T-0)=(0.1)(910)(25-T)+(0.2*4186)(25-T)
39. ### 1st and 2d order phase transitions

What's the difference between first and second order phase transitions. Could anyone give me some simple examples of both? Thanks.
40. ### Phase transitions: from the potential to the dynamical structure factor ?

Hi everybody, I've just started studying phase transitions and symmetry breaking for my PhD and I've met something I'd like to understand better. When we study the local potential vs. the order parameter in a structural phase transition I see there are two limiting cases, the one in which the...
41. ### Phase Transitions in Eutectic Combinations

for a given combination of metals phase transformations occurs at a variable temperature which is in between the phase change temperatures of constituting metals except at eutectic combination. why at this combination phase transformation is taking place at a constant temperature? what is the...
42. ### Phase Transitions and Chemical Potential

Hello, right now, I am learning thermodynamics with Reichl: "A modern Course in Statistical Physics" In chapter 3.C page 100 "classification of phase transitions", the text says: "As we change the independent intensive variables (p, T, x_1,... ,x_l) of a system, we reach values of the...
43. ### Phase Transitions and Critical Phenomena

Phase Transitions and Critical Phenomena! First 2 questions are not mathematical questions.So if there is someone who knows about what I am talking about i would be glad to hear what critical phenomena is about, i know i can use google for it and i actually did. But they are not really useful...
44. ### Phase Transitions and Critical Phenomena

Phase Transitions and Critical Phenomena! First 2 questions are not mathematical questions.So if there is someone who knows about what I am talking about i would be glad to hear the answers. Homework Statement (a) What is a renormalization-group transformation? (b) What is the...
45. ### Phase Transitions: Could Our Universe Be On the Brink of Change?

I've read a few books which talk about our universe's possible false vacuum energy state, and how our universe may, now or at some point in the future, undergo a phase transition as it moves from one vacuum state to a lower state via quantum tunneling, and how when such an event happens the...
46. ### Critical density of water - phase transitions

Hello people, I'm studying now phase transitions. I saw that the order parameter of water gas-liquid transition is the d[g]-d[c] or d[l]-d[c]. where d[g] is gas density d[l] is liquid density d[c] is the critical density Can someone please elaborate more about the critical density...
47. ### What Differentiates Crossovers from Phase Transitions in Thermodynamics?

Hi, Could anyone point me to a reference (textbook, review article...) with a clear explanation of the physics of crossovers? My main interest is to understand it in a microscopical level or in terms of a phenomenological effective potential a la second order phase transitions. I'd like to...
48. ### Phase Transition: Determine Order of Transitions

How does one determine the order of phase transitions?
49. ### Phase transitions from ising model

I'm having trouble understanding how changing parameters in the ising model leads to first order phase transitions. I understand how the intersection of \frac{kT}{2nJS} (\eta - \frac{g \mu_o H_o}{kT} ) = B_s(\eta) where B_s(\eta) is the Brouillion func leads (in the absence of a field H) to...
50. ### Phase transitions of space-time?

Don't you know what are http://motls.blogspot.com/2005/03/melting-crystals-and-quantum-foam.html" ? Horse-radish,:grumpy: you will understand that.:cry: What I imagine. At the beginning there was space-time and it was a solid, a crystal. Then there was the Big Bang, there came a Brane and...