Definitions for "Ideal gas"
a theoretical idea, an ideal gas is one that obeys perfectly the ideal gas law, PV = nRT, at all temperature and pressure conditions. Real gases (nitrogen, oxygen, etc.) behave almost exactly like ideal gases when the temperature and pressure are close to room conditions. An ideal gas would have no attractive forces between its molecules, and its molecules would take up no space (they would be mathematical points). This is not really true, since: all gases do have attractive forces between their molecules (they can all be condensed to liquids by cooling them enough that the attractive forces are able to make the molecules clump together as liquids) all gases molecules have some size, or you would be able to infinitely compress them (and you cannot) The ideal gas law can be derived from the assumptions that are made in the kinetic-molecular theory. When the temperature is quite a way above the molecule's boiling point, then attractive forces are almost meaningless. When the pressure is not too high, molecules have so much space between them that their small size is not relevant. Under these conditions, real gases obey the ideal gas law very closely.
follows the perfect gas laws without deviation. Practically, there are no ideal gases, but it is the basis from which calculations are made and corrections applied.
A gas that obeys all the postulates of the kinetic molecular theory. Real gases differ from the expected behavior of an ideal gas for two reasons: (1) the force of attraction between the particles in a gas is not quite zero, and (2) the volume of the particles in a gas is not quite zero.
Keywords:  concept, virtual
a virtual concept
a system consisting of N identical particles in a volume V