van der Waals equation
hamugeš-e van der Waals
Fr.: équation de van der Waals
An → equation of state that satisfactorily describes the behavior of → real gass over a wide range of temperatures and pressures. It is derived from considerations based on kinetic theory, taking into account to a first approximation the size of a molecule and the cohesive forces between molecules: (P + a / V2) (V - b) = RT, where P, V, and T are pressure, volume, and temperature and R the gas constant. a and b are characteristic constants for a given substance. For a = b = 0, the van der Waals equation reduces to the characteristic equation of an → ideal gas. See also → Dieterici equation.
Named after Dutch physicist Johannes Diderik van der Waals (1837-1923), Nobel Prize in Physics 1910; → equation.