4.2 Entropy 1). The thermodynamic definition of entropy a). Heat stimulates disorderly motion in the surroundings; work stimulates uniform motion of atoms in the surroundings, does not change the degree of disorder, and so does not change the entropy. b).A change in the extent to which energy is dispersed in a disorderly manner depends on the quantity of energy transferred as heat. 版权所有:华东理工大学物理化学教研
版权所有：华东理工大学物理化学教研室 16 1). The thermodynamic definition of entropy a). Heat stimulates disorderly motion in the surroundings; work stimulates uniform motion of atoms in the surroundings, does not change the degree of disorder, and so does not change the entropy. b). A change in the extent to which energy is dispersed in a disorderly manner depends on the quantity of energy transferred as heat. 4.2 Entropy
4.2 Entropy 1). The thermodynamic definition of entropy The thermodynamic definition of entropy is based on d do rev The units of entropy: JK- The units of Molar entropy:JK mol(the same as that of R) 版权所有:华东理工大学物理化学教研
版权所有：华东理工大学物理化学教研室 17 1). The thermodynamic definition of entropy T q S d rev d = The thermodynamic definition of entropy is based on The units of entropy: J K -1 . The units of Molar entropy: J K -1 mol –1 (the same as that of R) 4.2 Entropy
4.2 Entropy 1). The thermodynamic definition of entropy For a measurable change between two states i and f this expression integrates to f △S= rev To calculate the difference in entropy between any two states of a system, integrate the heat supplied at each stage of the path divided by the temperature at which the heat is supplied. 版权所有:华东理工大学物理化学教研
版权所有：华东理工大学物理化学教研室 18 1). The thermodynamic definition of entropy For a measurable change between two states i and f this expression integrates to: = f i d rev T q S To calculate the difference in entropy between any two states of a system, integrate the heat supplied at each stage of the path divided by the temperature at which the heat is supplied. 4.2 Entropy
D) Example Calculate the change in entropy when 50kJ of energy is transferred reversibly and isothermally as heat to a large block of copper at(0)℃,and(b)70℃ 版权所有:华东理工大学物理化学教研
版权所有：华东理工大学物理化学教研室 19 Example Calculate the change in entropy when 50kJ of energy is transferred reversibly and isothermally as heat to a large block of copper at (0) ℃, and (b) 70 ℃
D Example Method:△As=1 rev Answer: a)△S=4e_50×103J 1.8×102JK 273K bA、qm 50×103J =15×102JK1 T(70+273)K 版权所有:华东理工大学物理化学教研
版权所有：华东理工大学物理化学教研室 20 Example Answer: = = f i rev d rev T q q T S 1 Method: 2 1 3 rev 1.8 10 JK 273K 50 10 J Δ − = = = T q (a) S 2 1 3 rev 1.5 10 JK (70 273)K 50 10 J Δ − = + = = T q (b) S