Overview
This lecture introduces the fundamental concepts of thermodynamics, its scope, core principles, system types, properties, and the criteria for thermodynamic equilibrium, forming the basis for further study in the course.
Introduction to Thermodynamics
- Thermodynamics is derived from the Greek words 'therm' (heat) and 'dynamics' (force).
- Its scope includes energy transfer, energy conversion, and the laws governing these processes.
- Thermodynamics is based on fundamental natural laws observed through experience and experiments.
Directionality and Laws of Thermodynamics
- Natural processes occur with specific directionality; e.g., heat flows from high to low temperature.
- Not all energy conversions are equally efficient; 100% conversion of heat to work is impossible (Second Law).
- The Law of Conservation of Energy (First Law): energy can neither be created nor destroyed, only transformed.
Macroscopic vs. Microscopic Views
- Macroscopic (classical) thermodynamics studies matter without regard to molecular details; properties are measured or sensed.
- Microscopic (statistical) thermodynamics analyzes the behavior of molecules; macroscopic behavior is an average over molecular actions.
- Macroscopic theories must match observed behavior; microscopic models are calibrated to these.
Course Outline Highlights
- Basic definitions: systems, surroundings, properties, temperature, thermodynamic states.
- First Law: conservation of energy, internal energy, enthalpy, specific heats, open/closed systems.
- Second Law: directionality, reversibility, Carnot principle, entropy, availability, irreversibility.
- Thermodynamic property relations, pure substances, gases, gas mixtures, phase diagrams, and steam tables.
- Air standard and vapor cycles, thermodynamics of reactive systems, equilibrium conditions.
Types of Systems
- Control Mass System (Closed): Fixed mass and identity; no mass crosses the boundary, but energy can.
- Control Volume System (Open): Fixed region in space (control surface); allows both mass and energy transfer.
- Isolated System: No mass or energy transfer across the boundary.
Thermodynamic Properties
- Extensive Properties: Depend on mass (e.g., mass, volume, internal energy, enthalpy, entropy).
- Intensive Properties: Independent of mass (e.g., pressure, temperature, specific properties).
- Specific properties (per unit mass) are intensive versions of extensive properties.
Thermodynamic State & Equilibrium
- The state of a system is specified by independent properties uniform throughout and invariant with time.
- State variables are point functions that define system state; not all need to be specified, only a minimum set.
- Gibbs Phase Rule: Number of independent intensive properties, ( f = c - \phi + 2 ); for a single phase, single component, two properties suffice.
- Equilibrium requires uniform, unchanging properties; achieved either by isolation or matching properties with the surroundings (dead state).
- Practical systems are not fully in equilibrium; quasi-equilibrium is considered for analysis.
Key Terms & Definitions
- Thermodynamics — study of energy transfer and the laws governing it.
- System — defined quantity of matter or region in space for analysis.
- Surroundings — everything external to the system.
- Boundary — separates the system from its surroundings.
- Control Mass System — fixed mass, no mass transfer.
- Control Volume System — fixed space, allows mass/energy flow.
- Isolated System — no mass or energy exchange.
- Extensive Property — property dependent on system size or mass.
- Intensive Property — property independent of system size or mass.
- State — condition of a system as described by its properties.
- Quasi-Equilibrium — idealized process with properties nearly uniform and change slow enough to approximate equilibrium.
Action Items / Next Steps
- Review definitions of systems, properties, and equilibrium.
- Read recommended textbook chapters on system types and thermodynamic properties.
- Prepare questions on thermodynamic processes and equilibrium for next class.