Thermodynamics
1. Thermodynamic System and Surroundings
- A system is a part of the universe under observation.
- Everything outside the system is surroundings.
- Types of systems: Open, Closed, and Isolated.
2. Internal Energy (U)
- Sum of kinetic and potential energies of molecules inside the system.
- It changes when heat is added or work is done.
3. First Law of Thermodynamics
- Energy conservation principle applied to thermodynamic systems.
- ΔQ = ΔU + ΔW
- ΔQ = heat supplied, ΔU = change in internal energy, ΔW = work done by the system.
4. Specific Heat and Molar Specific Heat
- Specific heat: Heat required to raise temperature of 1 kg substance by 1 K.
- Q = mcΔT
- Molar specific heat: Heat required to raise temperature of 1 mole of substance by 1 K.
5. Thermodynamic Processes
- Isothermal: Temperature remains constant (ΔT = 0, ΔU = 0)
- Adiabatic: No heat exchange (ΔQ = 0)
- Isobaric: Pressure remains constant
- Isochoric: Volume remains constant (ΔW = 0)
6. Work Done in Thermodynamic Processes
- Work = PΔV (in isobaric process)
- In general: W = ∫PdV (area under P-V curve)
- Work is positive when done by the system, negative when done on the system.
7. Second Law of Thermodynamics
- Heat cannot flow from colder to hotter body without external work.
- Kelvin-Planck and Clausius statements express this law.
8. Reversible and Irreversible Processes
- Reversible: Can be reversed with no change in system or surroundings.
- Irreversible: Natural processes; cannot be completely reversed.
9. Heat Engine
- Converts heat energy into mechanical work.
- Absorbs heat Q1 from source, does work W, rejects Q2 to sink.
- Efficiency η = W / Q1 = 1 - (Q2 / Q1)
10. Refrigerator
- Device that transfers heat from cold region to hot region using external work.
- Coefficient of Performance (COP): β = Q2 / W