Physical Chemistry Glossary
25 essential terms — because precise language is the foundation of clear thinking in Physical Chemistry.
Showing 25 of 25 terms
The minimum energy required for a chemical reaction to proceed, representing the energy barrier on the reaction coordinate.
A thermodynamic process in which no heat is exchanged between the system and its surroundings ($q = 0$).
A fundamental physical constant ($k_B = 1.381 \times 10^{-23}$ J/K) that relates the average kinetic energy of particles in a gas to the temperature.
A substance that increases the rate of a chemical reaction by lowering the activation energy without being consumed in the process.
The partial molar Gibbs free energy of a component in a mixture; it describes how the free energy changes when the amount of that component changes.
Properties of solutions that depend on the ratio of solute to solvent particles, not on the identity of the solute.
A device that converts chemical energy into electrical energy (galvanic cell) or uses electrical energy to drive a non-spontaneous reaction (electrolytic cell).
A process that absorbs heat from the surroundings, characterized by a positive enthalpy change ($\Delta H > 0$).
A thermodynamic state function defined as $H = U + PV$, representing the total heat content of a system at constant pressure.
A thermodynamic quantity measuring the degree of energy dispersal or the number of accessible microstates in a system.
A dimensionless quantity ($K$) expressing the ratio of product to reactant activities at chemical equilibrium for a given reaction at a specific temperature.
A process that releases heat to the surroundings, characterized by a negative enthalpy change ($\Delta H < 0$).
An effective pressure that replaces the true pressure in thermodynamic equations for real gases, accounting for deviations from ideal behavior.
A thermodynamic potential ($G = H - TS$) used to predict the spontaneity of a process at constant temperature and pressure.
The time required for the concentration of a reactant to decrease to half its initial value, commonly used in first-order kinetics where $t_{1/2} = \frac{\ln 2}{k}$.
A thermodynamic process that occurs at constant temperature, often achieved by slow heat exchange with a large reservoir.
A specific arrangement of particles and energy in a system. The total number of microstates determines the entropy through Boltzmann's equation $S = k_B \ln W$.
A wavefunction describing the spatial distribution of an electron in a molecule, formed by the linear combination of atomic orbitals (LCAO).
The pressure required to prevent the net flow of solvent across a semipermeable membrane from a dilute to a concentrated solution.
The sum over all energy states of the Boltzmann factor $e^{-E/k_BT}$; it is the central quantity in statistical mechanics from which all thermodynamic properties can be derived.
A transformation from one phase of matter to another (solid, liquid, gas), occurring at specific conditions of temperature and pressure.
The proportionality constant $k$ in a rate law that relates reaction rate to reactant concentrations; it depends on temperature according to the Arrhenius equation.
The detailed sequence of elementary steps by which reactants are converted to products, including all intermediates and transition states.
The study of the interaction between matter and electromagnetic radiation, used to identify molecular structure, composition, and dynamics.
The highest-energy configuration along the reaction coordinate, representing the point of no return between reactants and products in an elementary reaction.