Gas Thermometry
Procedure
- Make sure that the water at the 100
station is actually boiling and that the water at the 0 contains ice. Turn on the vacuum pump. This experiment has a significant amount of time waiting for thermal equilibrium so please be making plots and thinking about your data as you go. - Insert the gas thermometer into the boiling water. Switch the valve to evacuate the gas thermometer with the vacuum pump. You don’t need a terribly low vacuum pressure here.
- Fill the thermometer with helium) to about -200 mmHg as read by the manometer mounted on the gas thermometer, indicating that the vacuum pressure in the thermometer is 200 mmHg below atmospheric pressure.
- Evacuate the gas thermometer again and refill it to about -200 mmHg. Evacuate again and fill again. Once the pressure settles, and you’re confident that your water is indeed boiling, record the pressure.
- Transfer the gas thermometer to the room temperature holding tank. It’s more efficient to warm up this water than to melt all of the ice in the 0 vessel. Wait a couple of minutes, then move your thermometer to the ice water.
- Once the pressure settles, ask your TA or lab technician to fill the next station with liquid nitrogen. Be sure to be wearing the cryo-gloves and eye protection when inserting or removing the gas thermometer from the liquid nitrogen.
- Insert the gas thermometer into the liquid nitrogen station and record the pressure once it settles.
- Perform this procedure with carbon dioxide BUT DO MORE EVACUATIONS AND REFILLS! Five in total. Helium is difficult to pump out because it’s so light, and even a small amount can skew your results here.
- Perform the procedure again with argon.