What is Phase transition: Definition and 60 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. A

    What determines a system to experience crossover or phase transition?

    More specifically, consider a Hamiltonian with a changeable parameter a. When changing a, the ground state of the system will change. In some cases, one phase crossovers to another, like in other cases, there's a phase transition. What factor determines the difference? Actually I am now working...
  2. M

    Phase transition of a rubber band model

    Homework Statement In class we studied a phase transition in a model of a rubber band. For small applied tensions, f < f^*, the Helmholtz free energy of the band as a function of the length is A_1(L) = (\kappa_1 /2)L^2, while at large applied tensions, f > f^*, it is A_2(L) = (\kappa_2 /2)L^2...
  3. J

    First order phase transition (van der waals gas)

    I am looking at some of the notes but don't quite understand this. What are the physical explanation of the graphs (Fig 4(a) and 4(b)) on Page 4 ? http://www.pma.caltech.edu/~mcc/Ph127/b/Lecture3.pdf" Why V_{g} decreases with temperature but V_{l} increases with temperature?
  4. J

    First order phase transition (van der waals gas)

    Homework Statement Give the physical explanation of the graphs (Fig 4(a) and 4(b)) on Page 4 http://www.pma.caltech.edu/~mcc/Ph127/b/Lecture3.pdf" Homework Equations 1) Why V_{g} decreases with temperature but V_{l} increases with temperature 2) Why must phase transition happen at...
  5. S

    Why phase transition not possible in one dimension?

    can anybody tell me why in general phase transition is not possible in one dimension? and for a lattice gas at low temp. why it requires long range order to occur phase transition?
  6. S

    Goldstone bosons 1st order phase transition

    Hi! I read in Zinn-Justin, that first order phase transitions always have a finite correlation length. Since correlation length is the inverse of the smallest physical mass within a model, this would mean that there can be no Goldstone bosons for a 1st order phase transition. How can that be...
  7. P

    Why Can't the 1D Ising Model Have a Phase Transition?

    Homework Statement Can someone please explain to me why there can never be a phase transition in the 1D Ising model? Homework Equations The Attempt at a Solution I have read the argument that if we start at T=0, all spins along the 1D chain are aligned (say up). Then if we...
  8. J

    Phase Transition: Entropy vs Pressure & Energy vs Volume

    hi, I find that the point where the entalphy vs pressure curves of diferent phases crystaline of material is crossing corresponding at the presure where occurs a phase transition, also i find that by meant of the solope of the tangent of the curves of energy vs volume i can determine the...
  9. L

    Why Do Substances Undergo Radical Changes During Phase Transitions?

    Hi, I was wondering, what actually are phase transitions such as fusion or evaporation? I know thermodynamic definitions such as points where the Gibbs energy is non-analytic or heat capacity changes abruptly, but these say nothing about mechanism. Why does a substance suddenly change its...
  10. N

    What is a second-order phase transition?

    May someone please explain to me or define what a second-order phase transition is? Thank you
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