1 / 6

Phase transitions

Phase transitions. Qualitative discussion: the 1-component system water. specific volume. Clausius-Clapeyron Equation. Heat Reservoir R. T=const. Consider a system of liquid & vapor phases in equilibrium at given P and T. P=const. vapor phase contains N 2 particles.

chuong
Download Presentation

Phase transitions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Phase transitions Qualitative discussion: the 1-component system water specific volume

  2. Clausius-Clapeyron Equation Heat Reservoir R T=const. Consider a system of liquid & vapor phases in equilibrium at given P and T P=const. vapor phase contains N2 particles constant # of particles N=N1+N2 liquid phase contains N1 particles P and T fixed System in a state of minimum Gibbs free energy Gibbs free energy/particle = chemical potential

  3. N2= N - N1 with const. for Let´s discuss G  minimum for g1>g2, g1<g2 and g1=g2 Index 1: liquid Index 2: vapor g1>g2 G at minimum for N1=0 N2=N (only vapor phase) 1 g1<g2 G at minimum for N1=N N2=0 (only liquid phase) 2 g1=g2 G at minimum for all N1, N2 with N1+N2=N 3 equilibrium of vapor & liquid phase

  4. P=const g g1(T,P)=1 g2(T,P)=2 T0 T P=P(T) = g2(T,P) g1(T,P) At the phase transition “vaporization curve” Note: g1=g2  1=2(see equilibrium conditions) How does the pressure change with temperature for two phases in equilibrium

  5. 1  T defining the transition line g1(T,P(T)) = g2(T,P(T)) With -s1 v1 -s2 v2 and we see From dg=-s dT+vdP volume/particle entropy/particle Latent heat: heat needed to change system from phase 1 to phase 2 = = Clausius-Clapeyron equation T=const. at phase transition

More Related