Welcome to the Pressure Chamber

Experimental Instructions

In this series of experiments, you will control the action of a piston in a pressure chamber which is filled with an ideal gas. The gas is defined by four states:

• Temperature
• Volume or density
• Pressure
• Molecular Weight

There are 3 possible experiments to do. In the third experiment, labelled Ideal Gas Law, you can select from the Red, Blue or Yellow gas containers. Each gas in those containers has a different molecular weight and hence each will respond differently under changing pressure conditions.

Be sure that the pressure in the chamber never exceeds 10 atmospheres !!!

If the pressure exceed this amount, the chamber will crack and the gas will leak out and your experiment will be over. Even though this is virtual gas, its effects could be unpredictable.

This experiment is setup so that changes in the state of the gas, e.g. its Temperature, Volume and Pressure, are automatically recorded on the graphical tool. This should guide the experimenter into understanding the relationships of the Ideal Gas Law.

First Experimental Procedure

• click on the button titled constant volume - you will see that the default variable to plot are now pressure vs temperature
• Now, for obscure reasons, you must prime the plotting tool.
• Grab the thermometer with your pointing device and raise the temperature to around 400 degrees and release the pointing device.
• Now lower the temperature back to around 300 degrees
• Now raise the temperature back to 400 degrees. You should now see a graph with one or possible 2 points plotted. From now one the graph will respond to each new temperature position.
• Change the temperature by moving the thermometer up and down; each time you release the pointing device a new point should appear. Do this until about 10 data points are plotted.
• What is the relationship between pressure and temperature at constant volume?
• Using this data, predict at what temperature the pressure will exceed 10 units
• You may test this prediction but be sure to reset the experiment after the chamber breaks.

Second Experimental Procedure

• Click on the button entitled constant temperature
• Now go to the control panel under the piston where there is a button with a single arrow on it. This is the rightmost of the two buttons.
• Each click of that button will depress the piston into the cylinder. Notice the pressure and volume meters change. Each click will plot 4 data points on the graph
• Being careful not to crack the cylinder with excess pressure, plot out the relation between pressure and volume as the temperature is held constant.
• From the form of the plot, can you guess the relation between pressure and volume when the temperature is held constant.

Third Experimental Procedure

• Click on the button titled Ideal Gas Law
• Select one of the gases, either Red , Blue , Yellow .
• These gasses have different molecular weights and hence have a different temperature and pressure response when the volume is changed. Each gas has the same starting temperature.
• Which of these gases can be raised to the highest temperature without breaking the cylinder?
• Estimate the temperature dependence on volume reduction for each of the three gases.
• If you were designing a pressure cylinder for the blue gas, approximately what pressure would it have to withstand when the temperature of that gas reaches 2000 K. What about for the yellow gas?
• Which of these gases has the lowest molecular weight?

End of This experiment.