Key Terms
- Avogadro’s number
- the number of molecules in one mole of a substance; particles/mole
- Boltzmann constant
- a physical constant that relates energy to temperature and appears in the ideal gas law;
- critical temperature
- at which the isotherm has a point with zero slope
- Dalton’s law of partial pressures
- physical law that states that the total pressure of a gas is the sum of partial pressures of the component gases
- degree of freedom
- independent kind of motion possessing energy, such as the kinetic energy of motion in one of the three orthogonal spatial directions
- equipartition theorem
- theorem that the energy of a classical thermodynamic system is shared equally among its degrees of freedom
- ideal gas
- gas at the limit of low density and high temperature
- ideal gas law
- physical law that relates the pressure and volume of a gas, far from liquefaction, to the number of gas molecules or number of moles of gas and the temperature of the gas
- internal energy
- sum of the mechanical energies of all of the molecules in it
- kinetic theory of gases
- theory that derives the macroscopic properties of gases from the motion of the molecules they consist of
- Maxwell-Boltzmann distribution
- function that can be integrated to give the probability of finding ideal gas molecules with speeds in the range between the limits of integration
- mean free path
- average distance between collisions of a particle
- mean free time
- average time between collisions of a particle
- mole
- quantity of a substance whose mass (in grams) is equal to its molecular mass
- most probable speed
- speed near which the speeds of most molecules are found, the peak of the speed distribution function
- partial pressure
- pressure a gas would create if it occupied the total volume of space available
- peak speed
- same as “most probable speed”
- pV diagram
- graph of pressure vs. volume
- root-mean-square (rms) speed
- square root of the average of the square (of a quantity)
- supercritical
- condition of a fluid being at such a high temperature and pressure that the liquid phase cannot exist
- universal gas constant
- R, the constant that appears in the ideal gas law expressed in terms of moles, given by
- van der Waals equation of state
- equation, typically approximate, which relates the pressure and volume of a gas to the number of gas molecules or number of moles of gas and the temperature of the gas
- vapor pressure
- partial pressure of a vapor at which it is in equilibrium with the liquid (or solid, in the case of sublimation) phase of the same substance