Chapter 24 Entropy and the second law of thermodynamics
Chapter 24 Entropy and the second law of thermodynamics
24-1 Two kinds of processes and entropy 1. Irreversible processes(不可逆过程) (a)All naturally occuring processes proceed in one direction only. They never, of their own accord, proceed in the opposite direction See动画库\力学夹\5-08过程的方向性 Such spontaneous one-way processes are irreversible (b) Although the wrong-way events do not occur, none of them would violate the law of conservation of energy
24-1 Two kinds of processes and entropy 1. Irreversible processes（不可逆过程） (a) “All naturally occuring processes proceed in one direction only. They never, of their own accord, proceed in the opposite direction.” Such spontaneous one-way processes are “irreversible”. (b) Although the “wrong-way” events do not occur, none of them would violate the law of conservation of energy. See动画库\力学夹\5-08过程的方向性
2. Reversible process.(可逆过程) See动画库\力学夹\5-09可逆过程 In reversible process, we make a small change in a system and its environment by reversing that change, the system and environment will return to their original conditions In a truly reversible process, there would be no friction, turbulence(a#), or other dissipative effects which will cause non-compensatory losses of energy
2. Reversible process（可逆过程） In reversible process, we make a small change in a system and its environment; by reversing that change, the system and environment will return to their original conditions. In a truly reversible process, there would be no friction, turbulence(紊乱), or other dissipative effects, which will cause non-compensatory losses of energy. See动画库\力学夹\5-09可逆过程
3. Entropy(s Entropy is a physical quantity that controls the direction of irreversible processes It is a property of the state of a system; like t, P, v, eint Entropy principle: If an irreversible process occurs in a closed system the entropy of that system al ways increases; it never decreases
3. Entropy (S) Entropy is a physical quantity that controls the direction of irreversible processes. It is a property of the state of a system; like T, P, V, Eint. Entropy principle: “If an irreversible process occurs in a closed system, the entropy of that system always increases; it never decreases
24-2 Entropy change for reversible processes 1.The definition of entropy change for a reversible process △S f d@(reversible)(24-1) T Here dQ is the increment of heat energy that is transferred into (or out)of the closed system at temperature T. If the process is isothermal △S (24-2) e>0,AS>0,the entropy of that system increases. if Q<0, AS<0)
24-2 Entropy change for reversible processes 1.The definition of entropy change for a reversible process: (reversible) (24-1) = f i T dQ S Here dQ is the increment of heat energy that is transferred into (or out) of the closed system at temperature T. If the process is isothermal, (24-2) , , the entropy of that system increases.( if Q<0, ). T Q S = Q 0 S 0 S 0