Answer to Question #269542 in Molecular Physics | Thermodynamics for Masuvhe

Question

What is a thermodynamic state?

What is a thermodynamic process?

Answer 1

In thermodynamics, a thermodynamic state of a system is its condition at a specific time; that is, fully identified by values of a suitable set of parameters known as state variables, state parameters or thermodynamic variables. Once such a set of values of thermodynamic variables has been specified for a system, the values of all thermodynamic properties of the system are uniquely determined. Usually, by default, a thermodynamic state is taken to be one of thermodynamic equilibrium. This means that the state is not merely the condition of the system at a specific time, but that the condition is the same, unchanging, over an indefinitely long duration of time.

A thermodynamic process is defined as a change from one equilibrium macrostate to another macrostate. The initial and final states are the defining elements of the process. During such a process, a system starts from an initial state i, described by a pressure pi, a volume V_i and a temperature T_i , passes through various quasistatic states to a final state f, described by a pressure pf, a volume V_f , and a temperature T_f. In this process energy may be transferred form or into the system and also work can be done by or on the system. One example of a thermodynamic process is increasing the pressure of a gas while maintaining a constant temperature. In following section, there are examples of thermodynamic processes that are of highest importance in engineering of heat engines.