A system changes state in a thermodynamic process by undergoing changes in its thermodynamic properties such as pressure, volume, temperature, and internal energy. Here’s a more detailed explanation:
- Initial and Final States:
A thermodynamic process connects an initial state of the system to a final state. Each state is defined by properties like pressure (P), volume (V), temperature (T), and internal energy (U). - Energy Transfer:
The change of state happens because of energy transfer between the system and its surroundings. This transfer can be in the form of:- Heat (Q): Energy transferred due to temperature difference.
- Work (W): Energy transferred when the system does work on the surroundings or vice versa (e.g., expansion or compression work).
- Path of the Process:
The system moves from the initial to final state through a series of intermediate states, which define the process path (isothermal, isobaric, adiabatic, etc.). The properties change continuously along this path. - State Functions:
The change in state depends only on the initial and final states, not on the path taken. For example, the change in internal energy (∆U) is the same regardless of the path, because internal energy is a state function. - Thermodynamic Equilibrium:
At each point along the process (in an idealized reversible process), the system is considered to be in thermodynamic equilibrium — meaning its properties are well-defined.