State (thermodynamics)

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The state of a system in thermodynamics is characterized by the specification of all state variables necessary for the delimitation from other states .

State variables include pressure , volume , temperature , amount of substance . These sizes are divided into extensive (quantity-dependent) and intensive (not quantity-dependent).

The individual states are often entered in a phase diagram . Depending on the plot, a single point usually corresponds to a state in the state space , but sometimes all points of a phase line or area also belong to a single state.

Statistical Physics

In statistical mechanics (statistical thermodynamics) there is the following distinction:

  • In the case of the microstate , the individual locations and impulses of all particles are given, so the microstate corresponds to a point in phase space .
  • the macrostate is an indication of mean values such as temperature, pressure and density. A macrostate includes all microstates that are compatible with the specified state variables.

Example coin toss

KZKKZZKK is a special microstate.
5x  K and 3x  Z is then the macrostate to which microstates belong (the number results from the combinatorics as a permutation of objects of two classes  K and  Z, taking into account the sequence).

See also