2013-3-6 Defining Entropy Change Equation 6.2a allows the change in entropy between two states to be determined by thinking of an internally reversible process between the two states.But since enropy isa property,that value ofenropy change applies to any process between the states-internally reversible or not. Entropy change is introduced by the integral of Eq.6.2 for which no accompanying physical picture is given.Still the aim of Chapter 6 is to demonstrate that entropy not only has physical significance but also is essential for thermodynamic analysis. Entropy Facts Entropy is an extensive property. Like any other extensive property,the change in entropy can be positive,negative,or zero: >0 S2-S:{=0 <0 By inspection of Eq.6.2a,units for entropy S are kJ/K and Btu/R. Units for specific entropy s are kJ/kg-K and Btu/Ib.R. 52013-3-6 5 Defining Entropy Change ►Equation 6.2a allows the change in entropy between two states to be determined by thinking of an internally reversible process between the two states. But since entropy is a property, that value of entropy change applies to any process between the states – internally reversible or not. ►Entropy change is introduced by the integral of Eq. 6.2a for which no accompanying physical picture is given. Still, the aim of Chapter 6 is to demonstrate that entropy not only has physical significance but also is essential for thermodynamic analysis. Entropy Facts ►Entropy is an extensive property. ►Like any other extensive property, the change in entropy can be positive, negative, or zero: ►By inspection of Eq. 6.2a, units for entropy S are kJ/K and Btu/oR. ►Units for specific entropy s are kJ/kg·K and Btu/lb· oR