9.1 Freezing Point Depression(2) S.J.T.0. Phase Transformation and Applications Page 15/36 At the temperature lower than Tm,the I.纯A在某个温度T熔化自由能变化 value of Gibbs free energy change for the L melting of pure A L=TnAS melung AGmcing=AHmclung-TASmelung-L-TASmcling L:latent heat of fusion L(T-T) Assuming no difference in heat capacity between liquid and solid AC,=0 AGmeling =RT In at.pureL(Tn-T) as,pure T At melting temperature Tm △melting =0 At the temperature below Tm,the activity of pure liquid A is greater than SJTU Thermodynamics of Materials Fall 2011 ©X.J.Jin Lecture 14 Phase diagram IPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Fall 2011 © X. J. Jin Lecture 14 Phase diagram I Page 15/36 9.1 Freezing Point Depression (2) At the temperature lower than Tm, the value of Gibbs free energy change for the melting of pure A ΔGmelting = ΔH melting −TΔS melting = L −TΔS melting L: latent heat of fusion Assuming no difference in heat capacity between liquid and solid Δ = 0 Cp At melting temperature Tm Δ = 0 Gmelting m m melting melting T L L = T ΔS or ΔS = m m m melting T L T T T T G L ( ) 1 − =⎟⎟⎠⎞ ⎜⎜⎝⎛ Δ = − m m s pure l pure melting T L T T a a G RT ( ) ln , , − Δ = = At the temperature below Tm, the activity of pure liquid A is greater than ? I. 纯A在某个温度T熔化自由能变化