Some examples of ideal gases are the oxygen, nitrogen, carbon dioxide and other gases in Earth's atmosphere. An ideal gas is a gas at low pressure and fairly high temperature in which the individual gas atoms or molecules can be assumed to be far apart and to not interact with each other.
The ideal gas law is an equation of state, that describes a relationship between gas pressure (P), volume (V), number of moles present (n) and temperature (T), as follows: PV = nRT. R is the universal gas constant that varies according to the units of the other factors in the equation. In words, the ideal gas law states that the molar density of the gas is proportional to the pressure and temperature. The ideal gas law is assumed to be valid at temperatures above room temperature (72 Fahrenheit) and pressures at or below atmospheric (1 atmosphere).
When the temperature and pressure are outside of this range, a correction factor Z must be introduced into the ideal gas law to account for the gas deviating from ideal behavior. Gases at low temperatures and/or high pressures can also be described with more complex equations of state that are valid at those conditions, such as the van der Waals or Virial equations.