States of Matter & Gas Laws — 60 Terms Defined

Frenkel Defect States of Matter & Gas Laws Dimensionless A point defect in which an ion leaves its lattice site and lodges in a nearby interstitial position.

Gas Density States of Matter & Gas Laws g/L The mass of a gas per unit volume, which for a gas depends strongly on temperature, pressure and molar mass. ρ = pM / RT

Gaseous State States of Matter & Gas Laws Dimensionless The state of matter in which particles are widely separated and move randomly at high speed, filling any container completely. pV = nRT

Gay-Lussac's Pressure Law States of Matter & Gas Laws Pa/K At constant volume, the pressure of a fixed mass of gas is directly proportional to its absolute temperature. p₁ / T₁ = p₂ / T₂

Graham's Law of Diffusion States of Matter & Gas Laws Dimensionless The rate at which a gas diffuses or effuses is inversely proportional to the square root of its molar mass. r₁ / r₂ = √(M₂ / M₁)

Hexagonal Close Packing States of Matter & Gas Laws Dimensionless A close-packed arrangement in which layers of spheres repeat in an ABAB sequence. 6 atoms per cell, 74% packing

Ideal Gas States of Matter & Gas Laws Dimensionless A hypothetical gas whose particles have zero volume and exert no intermolecular forces, obeying pV = nRT exactly at all conditions. pV = nRT

Ideal Gas Law States of Matter & Gas Laws Various The equation of state relating the pressure, volume, amount and absolute temperature of an ideal gas. pV = nRT

Interstitial Void States of Matter & Gas Laws Dimensionless An empty space between the packed spheres of a crystal lattice, capable of hosting a smaller ion or atom. r_void / r_sphere = 0.225 or 0.414

Isomorphism States of Matter & Gas Laws Dimensionless The property of two or more different substances crystallising in the same structural form.

Joule–Thomson Effect States of Matter & Gas Laws K/Pa The temperature change of a real gas when it expands through a throttle without exchanging heat or doing external work. μ = (∂T/∂p)_H

Kinetic Molecular Theory States of Matter & Gas Laws Dimensionless The model that explains gas behaviour in terms of large numbers of tiny particles in constant random motion. pV = ⅓ Nmc̄²

Latent Heat States of Matter & Gas Laws kJ/kg The energy absorbed or released when a substance changes state, with no accompanying change in temperature. q = m × L

Liquefaction of Gases States of Matter & Gas Laws K The conversion of a gas into a liquid by cooling below its critical temperature and applying pressure.

Liquid Crystal States of Matter & Gas Laws Dimensionless A state of matter that flows like a liquid but retains some of the molecular ordering of a crystal.

Liquid State States of Matter & Gas Laws Dimensionless The state of matter with a definite volume but no fixed shape, in which particles are close together yet free to move past one another.

Maxwell–Boltzmann Distribution States of Matter & Gas Laws Dimensionless The statistical distribution describing how molecular speeds are spread within a gas at a given temperature. f(v) ∝ v² e^(−mv² / 2kT)

Melting Point States of Matter & Gas Laws °C The temperature at which the solid and liquid phases of a substance coexist in equilibrium at a given pressure. ΔG = 0 at T_m

Packing Efficiency States of Matter & Gas Laws Dimensionless The percentage of the total volume of a unit cell that is actually occupied by the constituent particles. (volume of atoms / cell volume) × 100

Partial Pressure States of Matter & Gas Laws Pa The pressure that one component of a gas mixture would exert if it alone occupied the whole volume. p_i = x_i × p_total

Phase Diagram States of Matter & Gas Laws Pa, K A pressure–temperature plot showing which phase of a substance is thermodynamically stable under any given conditions.

Plasma States of Matter & Gas Laws K A state of matter consisting of a hot, electrically conducting mixture of ions and free electrons.

Polymorphism States of Matter & Gas Laws Dimensionless The ability of a single substance to exist in more than one crystalline form.

Real Gas States of Matter & Gas Laws Dimensionless An actual gas whose behaviour deviates from the ideal gas law because its molecules occupy volume and attract one another. Z = pV / nRT ≠ 1