A more useful unit is the bar which is 100,000 pascal, exactly. Historically, the atmosphere is the most common unit of pressure. Another common unit of pressure is the torr, or millimeter of mercury. 760 mm Hg Gas pressure is measured with a barometer , and pressures relative to atmospheric pressure are measured with a manometer . Temperature, T, is another gas property.
Thermal equilibrium exists if no heat flows between two objects which have a diathermic boundary.
Temperature can be measured with a thermometer, a device in which a substance, typically liquid mercury, expands with increasing temperature. Temperature can also be measured with thermocouples and thermistors. Celcius and Kelvin are the more important temperature scales. On the Kelvin scale, the minimum possible temperature, absolute zero , is the zero of the scale. The size of the Celcius and Kelvin degrees are the same.