Chemical Thermodynamics – Key Vocabulary

A concise set of vocabulary flashcards summarizing essential terms and definitions from the Chemical Thermodynamics lecture. These cards cover systems, properties, thermodynamic processes, energy functions, and criteria for spontaneity.

Thermodynamics

Branch of physical chemistry that studies energy and its transformations during physical and chemical processes.

System

The specific part of the universe chosen for thermodynamic study.

Surroundings

Everything external to the system that can exchange energy or matter with it.

Open System

A system that can exchange both matter and energy with its surroundings.

Closed System

A system that can exchange energy but not matter with its surroundings.

Isolated System

A system that exchanges neither matter nor energy with its surroundings.

Extensive Property

Property that depends on the amount of matter present (e.g., mass, volume).

Intensive Property

Property independent of the amount of matter (e.g., temperature, pressure, density).

State Function

Property that depends only on initial and final states, not on the path taken (e.g., ΔU, ΔH, ΔS).

Path Function

Property that depends on the specific pathway followed (e.g., heat q, work w).

Isothermal Process

Thermodynamic process that occurs at constant temperature (ΔT = 0).

Isobaric Process

Process that occurs at constant pressure (ΔP = 0).

Isochoric (Iso-volumetric) Process

Process that occurs at constant volume (ΔV = 0).

Adiabatic Process

Process with no heat exchange between system and surroundings (q = 0).

Reversible Process

Ideal process that can be reversed by infinitesimal changes, proceeding through equilibrium states.

Driving Force

Small applied force that pushes a reversible process forward.

Opposing Force

Force acting against the driving force in a reversible process.

Mechanical Equilibrium

Condition in which opposing forces balance; no net macroscopic change occurs.

Pressure-Volume (PV) Work

Work associated with volume change against an external pressure; w = −P_ext ΔV.

Free Expansion

Expansion against zero external pressure; w = 0.

Maximum Work

Greatest theoretical work obtained when a process is carried out reversibly.

Internal Energy (U)

Total kinetic and potential energy of particles in a system.

First Law of Thermodynamics

Energy cannot be created or destroyed; ΔU = q + w.

Enthalpy (H)

Heat content of a system at constant pressure; H = U + PV.

Enthalpy Change (ΔH)

Heat absorbed or released at constant pressure; ΔH = ΔU + Δ(PV).

Endothermic Reaction

Process with ΔH > 0; system absorbs heat.

Exothermic Reaction

Process with ΔH < 0; system releases heat.

Enthalpy of Fusion

Heat required to convert a solid to a liquid at constant P and T.

Enthalpy of Vaporization

Heat required to convert a liquid to a gas at constant P and T.

Enthalpy of Sublimation

Heat required to convert a solid directly to a gas.

Bond Enthalpy

Energy needed to break one mole of a specified bond in the gas phase.

Hess’s Law

Total enthalpy change of a reaction is the same, no matter how many steps the reaction is carried out in.

Entropy (S)

Measure of disorder or randomness in a system.

Second Law of Thermodynamics

Total entropy of system plus surroundings increases for a spontaneous process.

Gibbs Free Energy (G)

Criterion for spontaneity at constant T and P; G = H − TS.

ΔG and Spontaneity

ΔG < 0 spontaneous, ΔG = 0 equilibrium, ΔG > 0 non-spontaneous.

Gibbs-Helmholtz Equation

ΔG = ΔH − TΔS, relating free energy, enthalpy, entropy, and temperature.