We have seen that the pressure of all gases changes with temperature in a similar fashion for low pressures. Many of the properties of gases are common at low pressures (and high temperatures, that is, far above their condensation point). The pressure, volume and the temperature in kelvin of such a gas obey the equation
pV = nRT
where n is the amount of the gas in number of moles and R is a universal constant having value 8.314 J K-1 mol-1. The constant R is called the gas constant. This equation is known as ideal gas equation. A gas obeying this equation is called an ideal gas.
