Thermodynamics Concepts and Laws

Thermodynamics

Definition: Thermodynamics is the branch of physics that deals with heat, work, temperature, and the laws governing energy transfer.
Key Concepts:
- System and Surroundings:
  - System: The part of the universe being studied.
  - Surroundings: Everything outside the system.
  - Types of systems: Open, closed, and isolated.
- Types of Energy:
  - Kinetic Energy: Energy of motion.
  - Potential Energy: Stored energy based on position.
  - Internal Energy: Total energy contained within a system.
Laws of Thermodynamics:
1. Zeroth Law: If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other.
2. First Law (Law of Energy Conservation): Energy cannot be created or destroyed, only transformed. ΔU = Q - W (where ΔU is the change in internal energy, Q is heat added to the system, W is work done by the system).
3. Second Law: In any energy transfer, the total entropy of a closed system can never decrease, meaning energy transformations are not 100% efficient.
4. Third Law: As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.
Processes:
- Isothermal: Occurs at constant temperature (ΔT = 0).
- Adiabatic: No heat exchange with surroundings (Q = 0).
- Isochoric: Volume remains constant (W = 0).
- Isobaric: Pressure remains constant (typically involves heat exchange).
Thermodynamic Functions:
- Enthalpy (H): Total heat content of a system; H = U + PV (where P is pressure and V is volume).
- Entropy (S): Measure of disorder or randomness in a system; influences the direction of energy transformations.
- Free Energy (G and A): Gibbs Free Energy (G) indicates spontaneity at constant temperature and pressure, while Helmholtz Free Energy (A) indicates spontaneity at constant volume and temperature.
Applications:
- Heat engines (conversion of heat into work).
- Refrigerators and heat pumps (transfer of heat from cooler objects to warmer objects).
- Biological processes (metabolism and energy transformation in living organisms).
Equations:
- Clausius Inequality: ΔS ≥ Q/T (where T is temperature).
- Carnot Efficiency: η = 1 - (T_C/T_H) (where T_C is the absolute temperature of the cold reservoir and T_H the hot).

These notes provide a concise overview of the fundamental aspects of thermodynamics, essential for understanding energy systems and their applications.

Thermodynamics

Definition: Thermodynamics is the study of how energy is transferred and transformed in physical systems.
System and Surroundings:
- System: The specific part of the universe being studied.
- Surroundings: Everything outside the system.
- Types of systems: Open, closed, and isolated:
  - Open system: Allows transfer of both matter and energy.
  - Closed system: Allows energy transfer but not matter.
  - Isolated system: No exchange of energy or matter.

Types of Energy

Kinetic Energy: Energy of motion.
Potential Energy: Stored energy based on an object's position.
Internal Energy: The sum of all kinetic and potential energy within a system.

Laws of Thermodynamics

Zeroth Law: If two systems are at the same temperature as a third system, then they are all at the same temperature (thermal equilibrium).
First Law (Law of Energy Conservation): Energy cannot be created or destroyed, only transformed. This is represented by the equation: ΔU = Q - W, where:
- ΔU is the change in internal energy.
- Q is the heat added to the system.
- W is the work done by the system.
Second Law: In any energy transfer, the total entropy (disorder) of a closed system always increases. This means energy transformations are not 100% efficient and some energy is lost as unusable heat.
Third Law: As the temperature of a system approaches absolute zero, the entropy of a perfect crystal approaches zero. This is the point of absolute zero temperature (0 K).

Processes

Isothermal: Process occurs at a constant temperature (ΔT = 0).
Adiabatic: Process with no heat exchange with the surroundings (Q = 0).
Isochoric: Process where the volume remains constant (W = 0).
Isobaric: Process where the pressure remains constant, often involves heat exchange.

Thermodynamic Functions

Enthalpy (H): The total heat content of a system. It's calculated using the formula: H = U + PV, where:
- U is internal energy.
- P is pressure.
- V is volume.
Entropy (S): A measure of disorder or randomness in a system. It influences the direction of energy transformation and often increases as energy transfers occur.
Free Energy (G and A):
- Gibbs Free Energy (G): Indicates whether a process is spontaneous at constant temperature and pressure.
- Helmholtz Free Energy (A): Indicates whether a process is spontaneous at constant volume and temperature.

Applications

Heat engines: Convert heat into work.
Refrigerators and heat pumps: Transfer heat from cooler objects to warmer objects.
Biological processes: Metabolism and energy transformations in living organisms.

Equations

Clausius Inequality: ΔS ≥ Q/T. This shows that the change in entropy (ΔS) is greater than or equal to the heat transferred (Q) divided by the temperature (T).
Carnot Efficiency: η = 1 - (T_C/T_H). This equation calculates the theoretical maximum efficiency of a heat engine working between a hot reservoir (T_H) and a cold reservoir (T_C).