Thermodynamics and Surface Chemistry Vocabulary

Vocabulary flashcards generated from the lecture transcript covering core concepts in thermodynamics, laws of thermodynamics, free energy functions, and surface/interfacial phenomenon.

Hess's Law

A principle of thermodynamics stating that the total heat energy involved in converting a reactant to a product is the same whether the reaction occurs in a single step or through multiple intermediate steps ($\Delta H = h_1 + h_2 + h_3$).

Exothermic Reaction

A chemical reaction that releases heat energy, indicated in thermodynamics by a negative enthalpy sign ($-\Delta H$).

Endothermic Reaction

A chemical reaction that absorbs heat energy from its surroundings, indicated in thermodynamics by a positive enthalpy sign ($+\Delta H$).

Heat of Formation of Carbon Dioxide

The change in heat energy at room temperature when carbon completely reacts with oxygen to produce carbon dioxide, equal to $-94.052\,\text{kcal}$.

Avogadro's Number

The number of atoms or molecules present in one mole of any material, equal to $6.023 \times 10^{23}$.

Carnot Cycle

A theoretical four-step cyclical process representing an ideal gas engine that continues operating indefinitely without stopping under ideal, frictionless conditions.

Isothermal Process

A thermodynamic process that occurs at a constant temperature ($T_2$ to $T_2$ or $T_1$ to $T_1$) while pressure and volume change to do work.

Adiabatic Process

A thermodynamic process occurring in an insulated system where no transfer of heat or energy takes place ($Q = 0$).

Second Law of Thermodynamics (Heat Extraction Statement)

A statement of the second law asserting that energy in the form of heat or work cannot be extracted from a system unless a lower temperature cooling reservoir ($T_1$) is available.

Second Law of Thermodynamics (Isothermal Statement)

A statement asserting that heat energy cannot be removed from an isothermal system without putting external energy into the system.

Second Law of Thermodynamics (Work Conversion Statement)

A statement establishing that $100\%$ of heat energy can never be converted into $100\%$ useful work, as heat will always be lost or dissipated into the environment.

Entropy ($S$)

A thermodynamic property defined conceptually as the degree of randomness or disorder in a system, measured mathematically as heat added or removed per degree change in temperature ($\Delta S = \frac{\Delta Q}{\Delta T}$).

Spontaneous Process

An irreversible process that occurs naturally on its own, characterized by a positive change in entropy ($\Delta S > 0$) and a negative change in free energy ($\Delta G < 0$).

Third Law of Thermodynamics

A law stating that at absolute zero temperature ($-273.17^\circ\text{C}$ or $0\,\text{K}$), all molecular motion stops and every substance forms a perfect crystalline structure.

Gibbs Free Energy ($\Delta G$)

A thermodynamic function calculated by subtracting the product of temperature and entropy change from the enthalpy change ($\Delta G = \Delta H - T\Delta S$), used to predict the spontaneity of a process.

Helmholtz Free Energy

A free energy function used for thermodynamic systems existing at constant volume, substituting internal energy change ($\Delta E$) for enthalpy ($\Delta H$).

Van 't Hoff Equation

An equation derived from free energy that relates equilibrium constants ($K_1$, $K_2$) at different temperatures ($T_1$, $T_2$), allowing the calculation of equilibrium constant changes with temperature.

Interface

The common boundary existing between any two immiscible phases, such as liquid-liquid, solid-liquid, or liquid-gas.

Surface

A specific type of interface that exists between a liquid or solid phase and a gas (air) phase.

Surface Tension

The force per unit length (expressed as force applied per centimeter) acting at the boundary between a liquid phase and a gas phase due to unbalanced downward cohesive forces.

Interfacial Tension

The tension or energy existing at the common boundary between two immiscible liquid phases, such as oil and water.

Cohesive Forces

Intermolecular attractive forces occurring between similar or identical molecules in a system (such as water-water interactions).

Adhesive Forces

Intermolecular attractive forces occurring between different or non-similar molecules in a system (such as water-air or water-oil interactions).