Thermodynamics Laws and Concepts

Zeroth Law: Establishes thermal equilibrium; if A is in equilibrium with B, and B with C, then A is in equilibrium with C.
First Law: Energy cannot be created or destroyed (Law of Energy Conservation).
- Formula: ΔU = Q - W (Change in internal energy = heat added - work done by the system).
Second Law: Entropy of an isolated system always increases; energy transformations are not 100% efficient.
- Heat flows naturally from hot to cold bodies.
Third Law: As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.

Enthalpy (H): A measure of total heat content, defined as H = U + PV (internal energy + pressure × volume).
- Used in processes occurring at constant pressure.
Entropy (S): A measure of disorder or randomness in a system.
- ΔS = Q_rev / T (change in entropy = heat exchanged reversibly / temperature).
- Higher entropy indicates greater disorder and energy dispersal.

Carnot Cycle: Idealized cycle consisting of two isothermal and two adiabatic processes; sets the maximum efficiency for heat engines.
Otto Cycle: Ideal cycle for gasoline engines; consists of two adiabatic and two isochoric (constant volume) processes.
Diesel Cycle: Similar to Otto but uses constant pressure for heat addition.
Rankine Cycle: Used in steam power plants; consists of two isobaric (constant pressure) and two isentropic (constant entropy) processes.

Phase Diagram: A graphical representation showing the phases of a substance at various temperatures and pressures.
- Key points include triple point (where all three phases coexist) and critical point (end of phase boundary).
Phase Changes: Includes melting, freezing, evaporation, condensation, sublimation, and deposition.
- Energy changes during phase transitions are represented by latent heat (heat absorbed or released without temperature change).

Conduction: Transfer of heat through direct contact; governed by Fourier's law.
- Rate of heat transfer depends on temperature gradient, area, and material properties (thermal conductivity).
Convection: Transfer of heat by the movement of fluids; can be natural (due to density differences) or forced (using pumps or fans).
Radiation: Transfer of heat through electromagnetic waves; does not require a medium. Governed by Stefan-Boltzmann law.
- All objects emit radiation based on their temperature.

Zeroth Law: Fundamental principle establishing that if two systems are in thermal equilibrium with a third system, they are in equilibrium with each other.
First Law: Principle of energy conservation stating that energy cannot be created or annihilated, only transformed. Periodic changes in internal energy are governed by the equation ΔU = Q - W, where Q is heat added and W is work done by the system.
Second Law: States that in any energy transfer or transformation, the total entropy of an isolated system can only increase over time, indicating that energy conversions are never 100% efficient. It is highlighted that heat will naturally flow from a hotter object to a cooler one.
Third Law: As temperature approaches absolute zero, the entropy of a perfect crystalline structure also approaches zero, implying that there is a minimum possible entropy value.

Enthalpy (H): Represents the total heat content of a system, calculated using H = U + PV, where U is internal energy, P is pressure, and V is volume. It is particularly relevant in constant pressure processes.
Entropy (S): A quantification of disorder and randomness, with its change described by ΔS = Q_rev / T, indicating that it measures heat exchanged reversibly with temperature. Higher entropy suggests increased disorder and greater dispersal of energy.

Carnot Cycle: An idealized thermodynamic cycle consisting of two isothermal processes (constant temperature) and two adiabatic processes (no heat exchange), setting the theoretical maximum efficiency for heat engines.
Otto Cycle: Represents the ideal thermodynamic cycle found in gasoline engines, featuring two adiabatic (no heat exchange) and two isochoric (constant volume) processes.
Diesel Cycle: Similar structure to the Otto Cycle, but characterized by heat addition at constant pressure.
Rankine Cycle: This cycle is crucial for steam power generation, combining two isobaric (constant pressure) and two isentropic (constant entropy) processes.

Phase Diagram: Visual representation of the physical states of a substance across different temperature and pressure conditions. It includes key features like the triple point, where all three phases coexist, and the critical point, which marks the end of phase boundaries.
Phase Changes: Encompasses various transitions such as melting (solid to liquid), freezing (liquid to solid), evaporation (liquid to gas), condensation (gas to liquid), sublimation (solid to gas), and deposition (gas to solid).
Latent Heat: Represents the energy absorbed or released during phase transitions, occurring without any change in temperature.

Conduction: The process of heat transfer through direct physical contact between materials, described by Fourier's law. The rate is influenced by the temperature gradient, area of contact, and thermal conductivity of the materials involved.
Convection: Involves the transfer of heat through fluid movement, which can be natural (due to differences in density) or forced (through mechanical means like pumps or fans).
Radiation: The transfer of heat via electromagnetic waves, which does not require any medium to occur. Governed by the Stefan-Boltzmann law, it asserts that all objects radiate energy based on their temperature.