Constant Volume Thermometer

Consists of a brass sphere with a bicycle pump fitting on one end and a pressure gauge on the other. There are valves between the bicycle pump fitting and the sphere, and between the pressure gauge and the sphere.

Demonstrate how the ideal gas law may be used to construct a thermometer. Given constant volume, the pressure of a gas inside a closed container is dependent on the temperature by PV = nRT

• Constant volume thermometer
• Container with hot water
• Standard thermometer
• Bike pump

1. Ensure the end valve by the bike pump attachment is closed and the valve leading to the pressure gauge is open
2. Dip the bulb of the thermometer into various temperatures of hot water and show the effect on pressure

This demo can demonstrate the direct correlation between pressure and temperature. If needed, the bulb can be pressurized with the bike pump by opening the end valve.

When releasing the pressure inside the thermometer, remove the bike pump attachment (by unscrewing it's connection) as the valve won't allow the air to escape unless the center of the bike pump attachment is depressed.