在热力学系统中,热能不可能无限制地转化为功,它只有在高温向低温流动时才对外作功,当温差趋近于零,整个系统热量分布均匀时,就不再作功,而这时体系的热量依然存在。用这不作功的热量去除以温度差,所得的商值就为熵。自然界中有许多体系,不加外力,总能自动地单向地趋向于平衡状态。例如,两种不同的气体能自动混合均匀,而混 In the thermodynamic system, the thermal energy can not be converted into power indefinitely, it only work at low temperature when the high temperature to work, when the temperature is close to zero, the system heat evenly distributed, no longer work, and this When the system of heat still exists. This heat is used to remove the temperature difference, the resulting quotient is entropy. There are many systems in nature that can always automatically unidirectionally balance without external force. For example, two different gases can be mixed evenly and mixed