System
Region of space, enclosed by a boundary.
- Open system: Mass, energy transfer is possible. Aka. control volume.
- Closed system: Energy transfer is possible, mass transfer is not possible
- Isolated system: Energy and mass transfer are not possible
Boundary
Can be imaginary or physical. Boundary can be flexible.
Surroundings
Everything outside the system.
Properties
Aka. point functions. Explains the state of the system.
Intrinsic properties
Do not depend on the size of the system. Examples:
- temperature
- pressure
- specific heat capacity
Extensive properties
Depend on the size of the system. Examples:
- mass
- volume
- internal energy
- entropy
- enthalpy
- heat capacity
Specific properties
Mass-normalized properties. Intrinsic properties. Prefixed with “specific”. Lowercase alphabets are used to denote these.
Examples:
- specific heat capacity
- specific entropy
- specific enthalpy
- specific volume
- specific internal energy
- specific entropy
- specific enthalpy
- specific heat capacity
State
An instance of the system. Defined by its properties.
If a system is free from gravitational, magnetic, surface tension effects, etc, only 2 independent properties are needed to define the state.
Thermodynamic equilibrium
A state of a system that experiences no change.
Mechanical, phase, chemical, thermal equilibriums are required for thermodynamic equilibrium.
Thermodynamic process
A change in the state of a system.
A thermodynamic cycle is series of thermodynamic processes that returns the system to its initial state.
Common thermodynamic processes:
- Isothermal process: system temperature remains constant
- Adiabatic process: no heat transfer
- Isobaric process: system pressure remains constant
- Isochoric process: system volume remains constant
- Polytropic process: system pressure and volume are related by a power law
- Quasi-equilibrium process: system is in equilibrium throughout the process
Reversible process
A thermodynamic process that can be reversed without any trace on the surrounding. Ideal case.
Irreversible process
A thermodynamic process that cannot be reversed without any trace on the surrounding.
Steady flow process
A thermodynamic process in which, at any fixed point, they remain the same during the entire process.