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absolute temperature

temperature as compared to absolute zero, the cessation of all motion, even subatomic motion, measured in kelvins (K)

atmosphere (atm)

unit of pressure (force per unit area) equal to 760 mm Hg. The average atmospheric pressure at sea level is defined as 1 atmosphere.

Avogadro's law

law that states that equal volumes of gases at the same temperature and pressure have equal numbers of atoms or molecules, represented by the equation V1n1=V2n2\frac{V_1}{n_1}=\frac{V_2}{n_2}


unit of pressure equal to 100,000 Pa


open tube filled with liquid such as mercury and sealed at the other end under a vacuum, used to measure atmospheric pressure (of gas, in mm Hg)

Boyle's law

law that states that pressure of gas increases as volume decreases at constant temperature and moles of gas, represented by the equation P1V1=P2V2P_1V_1=P_2V_2

Charles's law

law that states that the volume of gas increases as temperature increases at constant pressure and moles of gas, represented by the equation V1T1=V2T2\frac{V_1}{T_1}=\frac{V_2}{T_2}

compressibility factor (Z)

describes how much a gas's behavior differs from ideal

Dalton's law of partial pressures

law that states that the total pressure of a mixture of ideal and nonreacting gases is the sum of the partial pressures of the individual gases


process by which gas moves from an area of higher concentration to an area of lower concentration


process by which gases move through small openings in solids, one particle at a time


state of matter that has neither a definite volume nor a definite shape, consisting of particles that are far apart and move randomly to fill their container

Gay-Lussac's law

law that states that for an ideal gas with constant mass and volume, the pressure exerted on the container is proportional to its absolute temperature, represented by the equation P1T1=P2T2\frac{P_1}{T_1}=\frac{P_2}{T_2}

Graham's law

law that states that the rate of effusion of a gas is inversely proportional to the square root of its mass, represented by the equation rate1rate2=M2M1\frac{{\rm{rate}}_1}{{\rm{rate}}_2}=\sqrt{\frac{M_2}{M_1}}

Henry's law

law that states that the amount of a gas that dissolves in a certain type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid at a specific temperature, represented by the equation C=kPgas C=kP_{\rm{gas}}

ideal gas

theoretical gas in which no forces are acting on the gas particles, and the particles do not take up space

ideal gas law

law that describes the behavior of ideal gases, represented by the equation PV=nRT PV=nRT

kinetic molecular theory

theory involving the relationship between temperature, pressure, and volume that states that the average kinetic energy of a gas is proportional to its temperature


instrument that measures gas pressure (in mm Hg) via a tube of liquid that is open at both ends

mean free path

average distance that a gas particle travels before colliding with another gas particle

mole fraction

concentration expressed as the moles of solvent divided by the total number of all moles in a solution

partial pressure

pressure of an ideal gas that contributes to the total pressure of a mixture of gases at constant temperature

pascal (Pa)

SI unit of gas pressure

pounds per square inch (psi)

unit that describes the pounds of force applied to a square inch (area) of a container


force applied perpendicular to a unit area of surface

standard molar volume

volume occupied by one mole of an ideal gas at STP (standard temperature and pressure), equal to 22.4 L

standard temperature and pressure (STP)

1 atmosphere (atm) pressure and 0°C (273.15 K) temperature


absolute unit of pressure, defined as 1/760 atmosphere (atm)

van der Waals equation

equation that accounts for intermolecular (nonideal) interactions between gases. It adjusts the ideal gas law to explain and predict the behavior of real gases.