Chapter 10 - Temperature and Kinetic Theory - Learning Path Questions and Exercises - Conceptual Questions - Page 381: 6

When heat is given to the gas, it expands as the kinetic energy of the molecules also increases. The molecules begins to hit the thermometer fluid with higher kinetic energy. Consequently the pressure on gas side increases since volume is constant. To overcome this extra pressure, the height H of thermometer fluid on other side increases. Thus H can be used to measure the temperature of the gas.

When heat is given to the gas, it expands as the kinetic energy of the molecules also increases. The molecules begins to hit the thermometer fluid with higher kinetic energy. Consequently the pressure on gas side increases since volume is constant. To overcome this extra pressure, the height H of thermometer fluid on other side increases. Thus H can be used to measure the temperature of the gas.