物理化学（共计3部分，共计611页）_部分2.pptx

1;2;;;;;Sketch for the distribution of energy;Sketch for the distribution of energy;(a) A ball resting on a warm surface; the atoms are under- going thermal motion; (b) For the ball to fly upwards, some of the random vibra-tional motion would have to change into coordinated, directed motion. ;The spontaneous changes are always accompanied by a dispersal of energy into a more disordered form.;The entropy of an isolated system increases in the course of a spontaneous change:;;The Second Law may be expressed in terms of the entropy, a state function that lets us assess whether one state is accessible from another by a spontaneous change. the Second Law uses the entropy to identify the spontaneous changes among those permissible changes. ;No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work.;;1). The thermodynamic definition of entropy;1). The thermodynamic definition of entropy;1). The thermodynamic definition of entropy; Example; Example 4.1- Calculating the entropy change for the isothermal expansion of a perfect gas;1). The thermodynamic definition of entropy;For any adiabatic change, qsur = 0, so; Illustration;2). The entropy as a state function;The Carnot cycle ;2). The entropy as a state function; 4.2 Entropy - The entropy as a state function;In the limit of infinitesimal cycles, the non-canceling edges of the Carnot cycles match the overall cycle exactly; the sum becomes an integral. This result implies that dS is an exact differential and S is state function.;;The Second Law may be expressed in terms of the entropy, a state function that lets us assess whether one state is accessible from another by a spontaneous change. the Second Law uses the entropy to identify the spontaneous changes among those permissible changes. ;The thermodynamic definition of entropy;The efficiency of a heat engine, ε :;Note that