热力学第二定律 熵的定义 Second law Uses entropy, S, to identify the spontaneous(irreversible) changes among the permissible changes Entropy is a measure of molecular disorder in a system, letting us assess whether one state is accessible from another via spontaneous change 需设计 w:有序,对S无贡献 熵的表达式 Why g, not w? rev △S re\ infinitessimal change measurable change熵的表达式 熵的定义 Why q, not w? 热力学第二定律 需设计 w: 有序, 对S无贡献