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Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,*,Chapter 7:Thermodynamic Driving Forces,“Thermodynamics is Two Laws and a Little Calculus,I.Definitions,Thermodynamic system-what we study,Open:can exchange U,V,n,Closed:can exchange U,V,but not n,Isolated:cannot exchange U,V,n,Surroundings-everything else,Boundaries,Semipermeable:allows some atoms to pass,Adiabatic:allows no heat to pass,Phase:homogeneous;uniform in p,T,A,More Definitions,Property:measurable of a system,Extensive=function of n,N,V,U,S,H,G,Intensive,function of n,N,T,P,A,Review,Degree of Freedom,Observation,(,max W),Driving Force,Ex.2.2,pressure,V,As V increases,gas expands.,p,Ex 2.3,diffusion,particle exch,N,j,As N,j,increases,gases mix and particle distrib,more uniform,Chem potential,j,Ex.3.4,U,Heat flows until T is uniform,T,II.Fundamental Thermodynamic Equations:Entropy,S(U,V,N,1,N,2,),dS=(,S/U),V,N,dU+,(,S/V),U,N,dV+,(,S/N,j,),V,U,Ni,dN,j,Eqn 7.1,dS=T,-1,dU+pT,-1,dV-,j,T,-1,dN,j,Eqn 7.5,Note:dV,dN,j,dU are differences in the degrees of freedom(DegF).p,j,T are the driving forces.As driving forces(DF)become more uniform,d(DegF),0.,Fundamental Thermodynamic Equations:Energy,U(S,V,N),dU=(,U/S),V,N,dS+,(,U/V),S,N,dV+,(,U/N,j,),V,S,Ni,dN,j,Eqn 7.2,dU,=TdS-pdV+,j,dN,j,Eqn,7.4,Note:(,U/S),V,N,=T means that the increase in energy per increase in entropy is positive;as S increases,so does U and in proportion to T.,III.Equilibrium:dS=0,Identify system,variables(DegF),constants,Identify constraints,relationships,Maximize total entropy,Apply constraint,Combine and rearrange to find requirement for equilibrium,Thermal Equilibrium(Ex.7.2),System=isolated=Object A(S,A,U,A,T,A,)+Object B(with similar properties);variables=U,A,U,B,;constant=V,N,S,T,(U)=S,A,+S,B,=S(,U,A,U,B,),U,T,=U,A,+U,B,=constant constraint dU=dU,A,+dU,B,=0 or dU,A,=-dU,B,To maximize entropy:dS,T,=0=,(,S,A,/,U,A,),V,N,dU,A,+,(,S,B,/,U,B,),V,N,dU,B,(,S,A,/,U,A,),V,N,=,(,S,B,/,U,B,),V,N,1/T,A,=1/T,B,Thermal Equilibrium(2),What does this mean?1/,T,A,=1/T,B,T,A,=T,B,In order to maximize entropy,energy or heat will transfer until the temperatures are equal.,Will heat flow from hot to cold or vice versa?Check dS,T,=(,1/T,A,-1/T,B,)dU,A,Mechanical Equilibrium(Ex.7.3),Complete,Chemical Equilibrium(Ex.7.5),Complete,Two Laws of Thermodynamics,First Law,dU=,q+,w,dU=T dS p dV(for closed system),Second Law,dS=,q/T,More Definitions,State variables(state functions),Process variables(path functions),Quasi-static process:such that properties,f(time,process speed),Reversible process:special case of quasi-static such that can be reversed with no entropy change(ideal case),Thermodynamic cycle:initial=final state,IV.Applications of Fundamental Thermodynamic Equations,Reversible and Irreversible,Work,w=-p,ext,dV(quasi-static process),V=0,p=0isobaric,T=0isothermal,q=0adiabatic,Entropy,Cycles,
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