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Related to ideal gas: Real gas
A gas having particles that have perfectly elastic collisions and negligible volume and intermolecular forces, thus exactly obeying the ideal gas law. No known gas is an ideal gas, but actual gases approximate this behavior at relatively low pressure and high temperature.
(Chemistry) 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, esp in thermometry. Also called: perfect gas
A gas in which there is no interaction between the individual molecules. Such a gas would obey the gas laws (such as Charles's law) exactly. No known gas qualifies as an ideal gas.