Fundamental Concepts of Thermodynamics Flashcards

Vocabulary flashcards covering the fundamental concepts, laws, and definitions from the DJJ30293 Thermodynamics lecture notes.

Thermodynamics

The study of energy, heat, and work on a system; derived from the Greek words therme (heat) and dynamis (power).

Zeroth Law of Thermodynamics

If two bodies are in thermal equilibrium with a third body, they are in thermal equilibrium with each other.

First Law of Thermodynamics

Energy can be neither created nor destroyed but can only be converted from one form to another.

Second Law of Thermodynamics

Energy has quality as well as quantity, and actual processes occur in the direction of decreasing quality of energy.

System

A quantity of matter or a region in space chosen for study.

Boundary

A real or imaginary surface that separates the system and its surroundings; it can be fixed or movable.

Surroundings

The mass or region outside the system.

Closed System

Also known as a control mass, it consists of a fixed amount of mass where no mass can cross the boundary, but energy (heat or work) can.

Open System

Also known as a control volume, it involves mass flow where both mass and energy can cross the boundary.

Intensive Properties

Properties that are independent of the mass of a system, such as temperature, pressure, and density.

Extensive Properties

Properties whose values depend on the size of the system, such as total mass, total volume, total momentum, and enthalpy.

Specific Properties

Extensive properties expressed per unit mass, such as specific volume ($v = m^3/kg$) or specific enthalpy ($h = kJ/kg$).

Kelvin Temperature Conversion

The formula used to convert Celsius to Kelvin: $T (K) = T (^{\circ}C) + 273$.

Pressure Unit Conversion

The equivalence where $1 \, \text{bar} = 100 \, \text{kN/m}^2$ or $100 \, \text{kPa}$.

State

The set of properties that completely describes the system’s condition at a given time.

Process

Any changes that a system undergoes from one equilibrium state to another.

Isobaric Process

A process during which the pressure ($P$) remains constant ($P_1 = P_2$).

Isochoric (Isometric) Process

A process during which the volume ($V$) remains constant ($V_1 = V_2$).

Isothermal Process

A process during which the temperature ($T$) remains constant ($T_1 = T_2$).

Adiabatic Process

A process during which the entropy ($s$) remains constant ($s_1 = s_2$) and no heat transfer occurs ($Q = 0$).

Polytropic Process

A process that follows the mathematical law $PV^n = C$.

Reversible Process

A process that can be reversed such that both the system and surroundings return to their original states with no other change in the universe.

Irreversible Process

A process that cannot return both the system and surroundings to original conditions; common factors include friction and heat transfer through a finite temperature difference.

Path

The series of states through which a system passes during a process.

Cycle

Occurs when a system returns to its initial state at the end of a process, making all final properties identical to initial properties.

Thermodynamic Equilibrium

A condition existing when a system is in thermal, mechanical, phase, and chemical equilibrium simultaneously.

Thermal Equilibrium

A state where the temperature is uniform throughout the entire system and no temperature differential exists.

Mechanical Equilibrium

A state related to pressure where there is no tendency for pressure to change at any point over time.

Phase Equilibrium

A state where different phases (solid, liquid, gas) of a substance coexist at equilibrium.

Chemical Equilibrium

A state where the concentrations of reactants and products have no tendency to change over time.

Internal Energy ($U$)

The sum of all microscopic forms of energy a fluid possesses and stores within itself; measured in $kJ$.

Kinetic Energy ($KE$)

A macroscopic form of energy resulting from a system's motion, expressed as $KE = m \left( \frac{C^2}{2} \right)$.

Potential Energy ($PE$)

A macroscopic form of energy resulting from a system's elevation in a gravitational field, expressed as $PE = mgz$.

Heat ($Q$)

Energy transferred between systems by virtue of a temperature difference; positive if flowing into the system and negative if flowing out.

Work ($W$)

Energy transfer defined as the product of force and distance moved in the direction of the force; positive if transferred from system to surroundings.