Gas Laws & Thermodynamics Essentials

27 vocabulary flashcards covering key gas laws, thermodynamic principles, and intermolecular forces from the lecture notes.

Pressure

Force exerted per unit area by gas particles colliding with container walls (P = F/A).

Common Units of Pressure

1 atmosphere (atm) = 760 millimeters of mercury (mm Hg) = 101.3 kilopascals (kPa) = 14.7 pounds per square inch (psi).

Boyle’s Law

For a fixed amount of gas at constant temperature, pressure and volume are inversely related: P₁V₁ = P₂V₂.

Charles’s Law

For a fixed amount of gas at constant pressure, volume and absolute temperature are directly related: V₁/T₁ = V₂/T₂.

Standard Temperature and Pressure (STP)

Reference conditions of 0 °C (273 K) and 1 atm pressure used for gas measurements.

Molar Volume at STP

One mole of an ideal gas occupies 22.4 L at STP.

Ideal Gas Law

Relates pressure, volume, moles, and temperature of a gas: PV = nRT.

Ideal Gas Constant (R)

Proportionality constant in PV = nRT; common value 0.0821 L·atm mol⁻¹ K⁻¹.

Gas Density (Ideal Gas)

d = PM/RT, where P is pressure, M molar mass, R the gas constant, and T temperature.

Graham’s Law of Effusion

The rate of effusion or diffusion of a gas is inversely proportional to the square root of its molar mass; lighter gases escape faster.

First Law of Thermodynamics

Energy cannot be created or destroyed; the change in internal energy ΔE = q + w (heat + work).

Specific Heat Equation

q = mCΔT, used to calculate heat absorbed or released given mass, specific heat capacity, and temperature change.

Heat

Energy transferred between objects due to a temperature difference.

Temperature

Measure of the average kinetic energy of particles in a substance.

Enthalpy (H)

Heat content of a system at constant pressure; a state function.

Standard Enthalpy of Reaction (ΔH_rxn)

Calculated from heats of formation: ΔHrxn = Σ n ΔHf(products) – Σ n ΔH_f(reactants).

Hess’s Law

The enthalpy change of an overall reaction equals the sum of enthalpy changes for individual steps.

Endothermic Process

Reaction or change that absorbs heat from surroundings (ΔH > 0).

Exothermic Process

Reaction or change that releases heat to surroundings (ΔH < 0).

Dispersion Forces

Weak intermolecular attractions present in all molecules due to instantaneous dipoles.

Dipole-Dipole Forces

Attractive forces between permanent dipoles of polar molecules.

Hydrogen Bonding

Strong dipole interaction when H is bonded to N, O, or F and attracted to a lone pair on N, O, or F in another molecule.

IMFs & Boiling/Melting Points

Stronger intermolecular forces lead to higher boiling and melting points.

Exothermic Phase Changes

Freezing, condensation, and deposition release heat to the surroundings.

Heating Curve Plateau

Flat segment where temperature remains constant while energy is used to overcome intermolecular forces during a phase change.

Triple Point

Specific temperature and pressure where solid, liquid, and gas phases coexist in equilibrium.

Supercritical Fluid

State of matter above its critical temperature and pressure where distinct liquid and gas phases do not exist, displaying properties of both.