When the temperature increases or decreases, the volume also increases or decreases as well as the pressure, as we have seen in Charles' Law and the aforementioned Gay-Lussac’s Law. The gas bulb is inserted into a bath or place we wish to find the temperature of, such as water.
T = 273.16 K lim P/Ptp as Ptp → 0 Operation.For equation 1, where a = 273.16 K, b = 0, Ptp is the pressure of the gas at the triple point of water, and P is the pressure of the gas at the temperature to be measured, we haveįor low pressure and high temperatures, where real gases behave like ideal gases, equation 1 becomes:
To recall, 273.16 K (Kelvin) is the temperature where water exists in an equilibrium state as a gas, liquid, and solid. Where a and b are constants determined from two fixed points, such as ice at 0oC and steam at 100oC.Īs mentioned previously, the constant volume gas thermometer uses values from the triple point of water to calibrate other thermometers. Calculationsįor a pressure P, the equation used to find the temperature T is Constant volume gas thermometers operate on the same principle, with the restrictions that the gas is at low pressure and the temperature of it is well above that of liquefaction. Conversely, when the temperature decreases, so does the pressure.
From the Law of Gay-Lussac, we know that when the temperature of an ideal gas increases, that there is a corresponding increase in pressure.