Ideal Gas Definition

bottle with gas inside
At low temperature, real gases behave like ideal gases. Greenhorn1/wikimedia commons/public domain

An ideal gas is a gas whose pressure P, volume V, and temperature T are related by the ideal gas law:

PV = nRT

where n is the number of moles of the gas and R is the ideal gas constant. Ideal gases are defined as having molecules of negligible size with an average molar kinetic energy dependent only on temperature. At a low temperature, most gases behave enough like ideal gases that the ideal gas law can be applied to them.

An ideal gas is also known as a perfect gas.