If P2 can be calculated using a manometer, the unknown temperature T2 is given by T2 = P2T1/P1. Where P1 and T1 represent the reference pressure and temperature, respectively and P2 and T2 represent the unknown pressure and temperature, respectively. Since it operates at constant volume, the equation can be written as: T or P1/T1 = P2/T2µP It is based on the ideal gas equation: PV = RT, for one mole of an ideal gas where P, V and T are the pressure, volume and temperature of the gas, respectively and R is the universal gas constant. The constant volume gas thermometer is more widely used. There are two main types of gas thermometer, one operating at constant volume and the other at constant pressure. Hydrogen and helium are also used as thermometric fluids in gas thermometer. It utilizes the expansion of a gas caused by the temperature changes to operate the pressure spring and indicate the temperature. AdvantagesĢ.Gas Expansion Thermometer (Gas Thermometer) Principle
The temperature limits of the mercury filled pressure thermometer are about -35 to 10000F. The thermal expansion of these liquid is about six times greater than that of mercury and from that standpoint their use is advantageous. Mercury is most widely used thermal liquid because of its wide temperature range.
A temperature increase at the bulb results in an expansion of the liquid which causes expansion of the bourdon tube or pressure spring and thus indicates the temperature. Working The bulb is filled with the thermal liquid at a high pressure. The equation indicates a linear relation which is not quite true as the coefficient of volumetric expansion, B varies slightly, with temperature. The relation between volume of expansion of a liquid and its temperature is given by the law of cubical expansion: Vf = V0(1+BT) Where Vf is the final volume, V0 is the initial volume, B is the mean coefficient of volumetric expansion and T is the temperature. It utilizes the volumetric expansion of a liquid caused by the temperature changes to operate the pressure spring and indicate the temperature. 1.Liquid Expansion Pressure Spring Thermometers What is the volume of a sample of ethane at 467 K and 1.1 atm if it occupies 405 mL at 298 K and 1.Pressure spring thermometers are of three types: Subtracting 273.15 from 239.8 K, we find that the temperature of the boiling ammonia on the Celsius scale is –33.4 ☌. Mathematically, this can be written as: $$V\ α\ T\quad or\quad V=constant Charles’s law states that the volume of a given amount of gas is directly proportional to its temperature on the kelvin scale when the pressure is held constant. The relationship between the volume and temperature of a given amount of gas at constant pressure is known as Charles’s law in recognition of the French scientist and balloon flight pioneer Jacques Alexandre César Charles. The line stops at 111 K because methane liquefies at this temperature when extrapolated, it intersects the graph’s origin, representing a temperature of absolute zero. If the temperature is in kelvin, volume and temperature are directly proportional. The volume and temperature are linearly related for 1 mole of methane gas at a constant pressure of 1 atm. Volume-temperature data for a 1-mole sample of methane gas at 1 atm are listed and graphed in. These examples of the effect of temperature on the volume of a given amount of a confined gas at constant pressure are true in general: The volume increases as the temperature increases, and decreases as the temperature decreases. This video shows how cooling and heating a gas causes its volume to decrease or increase, respectively. If we make the balloon very cold, it will shrink a great deal, and it expands again when it warms up.
If we put the balloon in a refrigerator, the gas inside gets cold and the balloon shrinks (although both the amount of gas and its pressure remain constant). If we fill a balloon with air and seal it, the balloon contains a specific amount of air at atmospheric pressure, let’s say 1 atm.