ideal gas

noun

, Physics.

1. a gas composed of molecules on which no forces act except upon collision with one another and with the walls of the container in which the gas is enclosed; a gas that obeys the ideal gas law.

ideal gas

noun

1. a hypothetical gas which obeys Boyle's law exactly at all temperatures and pressures, and which has internal energy that depends only upon the temperature. Measurements upon real gases are extrapolated to zero pressure to obtain results in agreement with theories relating to an ideal gas, especially in thermometry Also calledperfect gas

ideal gas

/ ī-dē′əl /

1. A hypothetical gas whose molecules bounce off each other (and the boundaries of their container) with perfect elasticity and have negligible size, and in which the intermolecular forces acting between molecules not in contact with each other are also negligible. Such a gas would obey the gas laws (such as Charles's law and Boyle's law) exactly at all temperatures and pressures. Most actual gases behave approximately as ideal gases, except at very low temperatures (when the potential energy of their intermolecular forces is high relative to the kinetic energy of the molecules and becomes significant), and under very high pressures (when the molecules are packed so close together that close-range intermolecular forces become significant).

Word History and Origins

Origin of ideal gas¹

First recorded in 1890–95