Thermodynamics Laws

Study Notes

Zeroth Law: If two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other.
First Law (Conservation of Energy): Energy cannot be created or destroyed, only converted from one form to another. ΔE = Q - W
- ΔE: change in energy
- Q: heat added to the system
- W: work done on the system
Second Law: The total entropy of an isolated system always increases over time. ΔS = ΔQ / T
- ΔS: change in entropy
- ΔQ: heat added to the system
- T: temperature
Third Law: As the temperature of a system approaches absolute zero, the entropy of the system approaches a minimum value.

Closed System: Energy can be transferred across boundaries, but matter cannot.
Open System: Both energy and matter can be transferred across boundaries.
Isolated System: No energy or matter can be transferred across boundaries.

Isothermal Process: Temperature remains constant.
Adiabatic Process: No heat is transferred between the system and surroundings.
Isobaric Process: Pressure remains constant.
Isochoric Process: Volume remains constant.
Cyclic Process: The system returns to its initial state after a series of changes.

Internal Energy (U): The total energy of a system, including kinetic energy, potential energy, and potential energy associated with the molecular structure.
Enthalpy (H): A measure of the total energy of a system, including internal energy and the energy associated with the pressure and volume of a system. H = U + pV
Entropy (S): A measure of the disorder or randomness of a system.
Free Energy (G): The energy available to do work in a system. G = H - TS

Heat Engines: Convert thermal energy into mechanical energy.
Refrigeration: Transfer heat from a colder body to a hotter body.
Thermodynamic Cycles: A series of processes used to convert energy from one form to another.

Zeroth Law: Thermal equilibrium is a transitive relation, meaning if two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other.
First Law (Conservation of Energy): Energy cannot be created or destroyed, only converted from one form to another, represented by the equation ΔE = Q - W, where ΔE is the change in energy, Q is the heat added to the system, and W is the work done on the system.
Second Law: The total entropy of an isolated system always increases over time, described by the equation ΔS = ΔQ / T, where ΔS is the change in entropy, ΔQ is the heat added to the system, and T is the temperature.
Third Law: As the temperature of a system approaches absolute zero, the entropy of the system approaches a minimum value.

Closed System: Energy can be transferred across boundaries, but matter cannot be transferred.
Open System: Both energy and matter can be transferred across boundaries.
Isolated System: No energy or matter can be transferred across boundaries.

Isothermal Process: Temperature remains constant during the process.
Adiabatic Process: No heat is transferred between the system and surroundings.
Isobaric Process: Pressure remains constant during the process.
Isochoric Process: Volume remains constant during the process.
Cyclic Process: The system returns to its initial state after a series of changes.

Internal Energy (U): The total energy of a system, including kinetic energy, potential energy, and potential energy associated with the molecular structure.
Enthalpy (H): A measure of the total energy of a system, including internal energy and the energy associated with the pressure and volume of a system, represented by the equation H = U + pV.
Entropy (S): A measure of the disorder or randomness of a system.
Free Energy (G): The energy available to do work in a system, represented by the equation G = H - TS.

Heat Engines: Devices that convert thermal energy into mechanical energy.
Refrigeration: The process of transferring heat from a colder body to a hotter body.
Thermodynamic Cycles: A series of processes used to convert energy from one form to another.