Thermodynamics and Phase Rule Overview

Thermodynamics and Phase Rule

• Thermodynamics is the science of the relationship between heat, work, and the properties of systems.
• It allows us to understand energy flow into or out of a system.
• Important factors in thermodynamics include studying changes in system properties like temperature (T), volume (V), and composition.
• The phase rule equation, one-component systems, two-component systems (solid and liquid), compound formation, solid solutions, and three-component systems are part of the phase rule.
• Heat, energy, and work are fundamental concepts in thermodynamics.
• The laws of thermodynamics (first, second, and third), heat capacities, adiabatic processes, Joule-Thomson effect, thermochemistry, and the Carnot cycle are key areas of study.
• Entropy and free energy, along with properties of solutions, complete the study.
• Thermodynamics is crucial in designing various systems, including automotive engines, rockets, jet engines, power plants, solar collectors, and many more, up to complex systems like airplanes.
• Heat and work are forms of energy transfer.
• Work is done on a system by surroundings if the energy of the system increases, it's positive; if decreased, it's negative.
• Heat (q) is positive when it flows from surroundings into the system, and negative if it flows out of the system.

Basic Concepts of Thermodynamics

• Thermodynamics studies systems and their interactions to benefit humanity.
• Applying thermodynamic concepts, it's helpful to analyze physical or chemical changes under given conditions.
• Derivation of thermodynamic laws like those in physical chemistry is a core application.
• Thermodynamics is macroscopic; it doesn't account for the behavior of individual atoms or molecules.
• It deals with the rate of physical or chemical reactions (time factor).

System, Boundary, and Surroundings

• A system is the part of the universe under study.
• The boundary separates the system from its surroundings.
• The surroundings are everything outside the system.

Homogeneous and Heterogeneous Systems

• Homogeneous systems have uniform composition throughout.
• Heterogeneous systems have non-uniform composition, meaning different phases are present.

Types of Thermodynamic Systems

• Isolated systems do not exchange matter or energy with their surroundings.
• Closed systems exchange energy but not matter.
• Open systems exchange both matter and energy.
• Adiabatic systems don't exchange heat with their surroundings, so dq=0.

Intensive and Extensive Properties

• Intensive properties do not depend on the system's size. Examples: temperature and density,
• Extensive properties depend on the system's size. Examples: volume, mass, and energy.

State of a System

• The state of a system is described by its properties (pressure, temperature, volume, mass).
• For a gas in a standard state, PV = RT.

Equilibrium and Non-equilibrium States

• Equilibrium: All properties and state variables are uniform throughout the system
• Non-equilibrium: If state variables exhibit different values of the system.

Criteria for Equilibrium

• Thermal equilibrium: Uniform temperature throughout the system and its surroundings.
• Mechanical equilibrium: No net forces or pressure differences within or between the system and its surroundings.
• Chemical equilibrium: Uniform composition and no net chemical changes.

Types of Thermodynamic Processes

• Isothermal processes occur at a constant temperature (dT = 0).
• Adiabatic processes do not exchange heat with the surroundings (dq = 0).
• Isobaric processes occur at a constant pressure (dp = 0).
• Isochoric processes occur at a constant volume (dV = 0).
• Cyclic processes return to the initial state after a series of processes (dE = 0, dH = 0).

Reversible and Irreversible Processes

• Reversible process: A process that can be reversed with minimal changes in the system to return to its original state.
• Irreversible process: A process that cannot be reversed without substantial changes and substantial interaction of the system with the surroundings.

Nature of Heat and Work

• Energy transfer during a change in system state happens as heat or work.
• Units of work: Erg (CGS) and Joule (SI).
• Units of heat: Calorie (CGS) and Joule (SI).
• The relationship between calories and joules is 1 calorie = 4.184 joules.

Sign Conventions

• Heat transfer from the surroundings to the system (+q) and from the system to surroundings (-q).
• Work done on the system (+w) and work done by the system (-w).