<P> For example , gas in a container with known volume , pressure , and energy could have an enormous number of possible configurations of the collection of individual gas molecules . At equilibrium , each instantaneous configuration of the gas may be regarded as random . Entropy may be understood as a measure of disorder within a macroscopic system . The second law of thermodynamics states that an isolated system 's entropy never decreases . Such systems spontaneously evolve towards thermodynamic equilibrium , the state with maximum entropy . Non-isolated systems may lose entropy , provided their environment 's entropy increases by at least that amount . Since entropy is a function of the state of the system , a change in entropy of a system is determined by its initial and final states . This applies whether the process is reversible or irreversible . However , irreversible processes increase the combined entropy of the system and its environment . </P>
<P> For example , gas in a container with known volume , pressure , and energy could have an enormous number of possible configurations of the collection of individual gas molecules . At equilibrium , each instantaneous configuration of the gas may be regarded as random . Entropy may be understood as a measure of disorder within a macroscopic system . The second law of thermodynamics states that an isolated system 's entropy never decreases . Such systems spontaneously evolve towards thermodynamic equilibrium , the state with maximum entropy . Non-isolated systems may lose entropy , provided their environment 's entropy increases by at least that amount . Since entropy is a function of the state of the system , a change in entropy of a system is determined by its initial and final states . This applies whether the process is reversible or irreversible . However , irreversible processes increase the combined entropy of the system and its environment . </P>
entropy can be expressed as a function of
entropy can be expressed as a function of
the state of the system
the state of the system