CHB-201: Physical Chemistry-I (Thermodynamics) Vocabulary

Flashcards covering basic terms, laws, and equations from the Physical Chemistry-I (Thermodynamics) lecture notes.

Thermodynamics

The study of the flow of heat, dealing with energy changes accompanying all types of physical and chemical processes.

System

Any specified portion of the universe or matter, real or imaginary, separated from the rest of the universe, selected for thermodynamic treatment.

Surroundings

The rest of the universe outside the system which may exchange matter or energy or both with the system.

Open system

A system which can exchange both energy and matter with its surroundings, such as water in an open beaker.

Closed system

A system that can exchange only energy (heat and work) and not matter with its surroundings.

Isolated system

A system which can neither exchange matter nor energy with its surroundings, such as reactants in a thermos flask.

Macroscopic system

A system consisting of a large number of atoms, particles, molecules, or radicals.

Macroscopic properties

Properties of a macroscopic system such as pressure, temperature, volume, density, and viscosity.

State of a system

Defined by macroscopic properties; when these properties have specific or definite values, the system is in a definite state.

Thermodynamic Equilibrium

A state where macroscopic properties like temperature, pressure, volume, and composition do not change with time.

Thermal equilibrium

A condition where the system's temperature does not change relative to the temperature of the surroundings.

Mechanical equilibrium

A state in which a system does not perform any mechanical work.

Chemical equilibrium

A state where a system's chemical composition remains constant throughout and does not change with time.

Extensive property

Properties that depend on the quantity or amount of matter present in the system, such as mass, volume, and enthalpy.

Intensive property

Properties that do not depend on the quantity or amount of matter present, such as temperature, pressure, density, and surface tension.

State function

A thermodynamic property whose value depends only on the initial and final states of the system, not the path taken, such as pressure or internal energy.

Path function

A property that depends on the specific path followed when a system passes from one state to another, such as work done.

Thermodynamic process

The operation by which a thermodynamic system changes from one state to another.

Isothermal process

A process where the temperature of the system remains constant throughout ($dT = 0$).

Adiabatic process

A process where no heat enters or leaves the system during any stage ($dq = 0$).

Isobaric process

A process where the pressure of the system remains constant throughout ($dP = 0$).

Isochoric process

A process where the volume of the system remains constant throughout ($dV = 0$).

Cyclic process

A process where a system returns to its initial state after completing various stages.

Reversible process

A process carried out infinitesimally slowly so that at every stage the system remains in equilibrium with the surroundings; it requires infinite time.

Irreversible process

A process not carried out infinitesimally slowly, meaning the system does not remain in equilibrium with surroundings at every stage.

First Law of Thermodynamics

States that energy can neither be created nor destroyed, only transformed; also known as the law of conservation of energy ($\Delta U = q + w$).

Internal Energy ($U$)

The sum of all possible types of energy present in a system; it is a state function.

Enthalpy ($H$)

The total heat content of a system, defined as the internal energy plus the product of pressure and volume ($H = U + PV$).

Heat Capacity ($C$)

The amount of heat ($q$) required to raise the temperature of a mass by a specific difference ($C = dq/dT$).

Specific heat

The heat capacity of a system when the mass is exactly one gram.

Molar heat capacity

The heat capacity of a system when the mass is exactly one mole.

Joule-Thomson effect

The cooling (or warming) of a gas as it expands adiabatically through a porous plug into a region of low pressure or vacuum.

Inversion temperature ($T_i$)

The temperature at which the Joule-Thomson coefficient changes sign ($T_i = 2a/Rb$).

Carnot Cycle

A reversible cycle consisting of four strokes: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression.

Entropy ($S$)

A state function that measures the disorder or randomness of a system ($dS = dq_{rev}/T$).

Second Law of Thermodynamics

States that the entropy of the entire universe always increases over time and changes in universal entropy can never be negative.

Third Law of Thermodynamics

States that the entropy of a perfectly crystalline solid at absolute zero ($0\,K$) is zero.

Work function ($A$)

Also known as Helmholtz free energy, defined as $A = U - TS$. Decrease in $A$ gives maximum work.

Gibbs free energy ($G$)

Defined as $G = H - TS$, it measures the maximum net work obtainable at constant temperature and pressure.

Maxwell Relations

A set of thermodynamic equations relating entropy, volume, temperature, and pressure derived from internal energy, enthalpy, and free energies.

Gibbs-Helmholtz Equation

Relates the change in Gibbs energy to temperature dependence and enthalpy change: $\Delta G = \Delta H + T[\partial(\Delta G)/\partial T]_P$.

Van't Hoff Equation

Relates the change in the equilibrium constant ($K_p$) of a chemical reaction to the change in temperature ($T$).

Nernst Heat Theorem

States that as the temperature is lowered toward absolute zero, the value of $\partial(\Delta G)/\partial T$ gradually approaches zero.

Residual Entropy

The finite entropy remaining in a crystal at $0\,K$ caused by alternative arrangements of molecules, such as in carbon monoxide ($CO$).