Pressure-Volume Relationship in Gases
- A 20 mL gas syringe
- Vernier Gas Pressure Sensor
-Vernier Logger Pro software
To begin this experiment, prepare the syringe with the slider set to to 10 mL mark, at this point you will put your plug on the nozzle of the syringe, which should be attached to the gas pressure sensor. At this point you will press COLLECT on the Logger Pro top menu, this will record the normal pressure at the natural, unstressed volume in the syringe. After waiting for roughly 10-15 seconds, press KEEP on the top menu of Logger pro, your data should be recorded in the table to the left hand side of your screen. Keep in mind that your volume is not the exact value of the volume in your syringe, to find the adjusted values for value, add .8 mL to your original volume of gas. This accounts for the small amount of air held in the tip on the nozzle.
Now that you have your first value, repeat the same process for step 2 where the volume of air is 7 mL. WITHOUT REMOVING THE CAP, depress the slider to the 7 mL mark. and line up the holes on the slider and the body of the syringe to place a holding pin through the aligned slots. (The best way to do so is to have one person align the slots and hold the slider down while another person places the pin) Once the pin is in place, press COLLECT on your top menu bar and wait 10-15 seconds once again. Do not forget to press collect and check that your data has been recorded on the data table to the left. Once the data has been collected, repeat the same process for the volume of 9 mL.
The same process will be repeated for the remainder of the tested volumes, the only difference being that instead of pressing the slider down, you will be pulling the slider up toward the top of the syringe. Once again, the best method is to have one person hold the slider while the other places the pin. Repeat the previous tests for the volumes of 11 mL, 13 mL, 15 mL, 17 mL, and 19 mL.
Once finished, you should see your data in the table to the left. The numbers in the left column will show the volume values, the column on the right will show the pressure values. Next, you will find a line of best fit for your graph; click the CURVE FIT button on the top menu bar, a menu should appear in the center of your screen. Choose variable power from the list in the drop down bar in the lower left corner, also edit the POWER EDIT box, typing either 1 if the relationship shown is direct, or -1 if it is inverse. You will be given a TRY FIT option, which will display a curve, adjust your curve until you see that the shown curve closely fits your data. Once you have found your best fit curve, proceed to PROCESSING THE DATA.