PVT Lab
Part 1: P vs V
The question: What is the relationship between volume and pressure for a gas in a
sealed container?
For this experiment you will need the following equipment:
1.
2.
3.
4.
Vernier Gas Pressure Sensor
Lab-Pro box, computer, and logger-pro software
25mL syringe with Luer-lock tip
PV.cmbl file (find this on my website)
Procedure:
1. Connect the gas pressure sensor to the lab-pro and the lab-pro to the computer.
2. Open the PV file.
3. With the syringe set at 15mL, connect it to the gas pressure sensor using the Luer-lock
connector
4. Moving the syringe in 1 mL increments, manually load a value in the volume cell that
corresponds with the volume on the syringe, then press the [Keep] button. Do this each
time you move to a new volume position. Remember to record your volume
amounts to proper sig figs.
5. Repeat this process for volume values between 8 mL and
20 mL.
6. Draw the graph you see on the screen in your notebook along with the data form the data table
on a page labeled Pressure vs. Volume. Describe what the relationship between volume and
pressure appears to be (when one goes up does the other follow? Do they change by the same
amounts?, etc)
7. It is now your job to determine the equation for the graph you have created. Keep in mind that
the physical world tends to favor simple relationships (not complex quadratics for example).
With this in mind do the following:
a. Using your analysis in step 6 select a simple relationship that seems to make sense. Hit
the “Try Fit” button and look at the Root Mean Square Error (RMSE) at the bottom right.
This value will be very low if the equation appears correct. Once you think you have the
proper equation write it down and get your instructor to ensure you are correct.
b. Select Data, New Calculated Column and enter the equation your instructor approved.
Write an equation that appears to represent your dataset. Note that the formula is
simply what you want your new column of data to be, for example: 1/”X”
c. Highlight your calculated column and insert a new graph. Set the x axis as equal to
pressure in mmHg. Analyze this graph. If it has a high correlation with a linear
relationship then you have found the true relationship between the two variables. Draw
this graph in your notebook.
d. Is there a constant produced by the multiplication of pressure in mmHg and volume in
mL? Identify it using proper significant figures. Does this value roughly match the
constant a determined in your calculation? Is this value consistent? If it varies what does
that mean?
8. Check with your instructor
Part 2: P vs N
The question: “What is the relationship between pressure and number of particles
for a gas in a sealed container?”
For this experiment you will need the following equipment:
1.
2.
3.
4.
Vernier Gas Pressure Sensor
Lab-Pro box, computer, and logger-pro software
25mL syringe with Luer-lock tip
P-n.cmbl file (find this on my website)
Procedure:
1.
2.
3.
4.
Connect the gas pressure sensor to the lab-pro and the lab-pro to the computer.
Open the PN file.
Pick a standard reference point on your syringe (10 mL works great).
Using your defined number of particle volume units, set your syringe some number of these
units past your reference point (larger mL value) in open air then connect the syringe via the
luer-lock connector to the gas pressure sensor.
5. Move the syringe to your reference point and manually load a value in the N cell that
corresponds with the defined particle volume units you have moved to the reference point.
When the adjustment is done, click the KEEP button, enter the number of
particles in the syringe (in “puff” units), and hit enter.
6. Repeat this process for a variety of different particle volume units
7. Draw the graph you see on the screen in your notebook along with the data form the data table
on a page labeled Pressure vs. Number of Particles. Describe what the relationship between
pressure and the number of particles appears to be (when one goes up does the other follow?
Do they change by the same amounts?, etc). Describe this relationship with both an equation or
proportion, and in words. Note: if the graph appears linear, a linear fit with a high correlation is
appropriate. Remember, the x and y axis are describing things – ensure your equations specify
these descriptions.
8. Check with your instructor
Part 3: P vs T
The question: “How does temperature affect the pressure of a gas in a sealed
container?”
For this experiment you will need the following equipment:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Vernier Gas Pressure Sensor
Vernier Temperature Probe
Interface and computer with Logger Pro software
One 25mL test tube
Salt & Ice mixture
One-hole stopper fitted with a luer-lock stopcock.
A single 250mL Erlenmeyer flask used as a water bath at various temperatures
Large beaker of water on a hot plate kept at a simmer (may be shared between lab groups)
P-T.cmbl file (find this on my website)
Procedure:
1. Connect the gas pressure sensor and temperature sensor to the lab-pro and the lab-pro to the
computer.
2. Open the PT file.
3. Place the stopper in the test tube, then connect the hose to the pressure sensor using the luerlock connector.
4. Obtain some hot water from the front of the room and fill a 250 mL Erlenmeyer flask about 7/8th
full. Place your temperature probe inside the flask.
5. Submerge the tes tube in the Erlenmeyer flask, bobbing it up and down to attempt to quickly
equalize temperatures in both the flask and test tube. Ensure the stopper does not get loose, if
this happens start over.
6. After about 1 minute of bobbing press the “keep” button to log the data.
7. Lower the temp of the water in the beaker by removing some hot water and adding some cold
water. Temp target is between 50 and 60 degrees C. Repeat procedure above, logging data by
pressing the “Keep” button.
8. Repeat this process for a temp of around 40 degrees C and near 20 degrees C.
9. To obtain a temperature near 0 degrees C, use a mixture of ice and salt in the Erlenmeyer flask.
This will be your last reading.
10. Draw the graph you see on the screen in your notebook along with the data form the data table
on a page labeled Pressure vs. Temperature. Describe what the relationship between pressure
and temperature appears to be (when one goes up does the other follow? Do they change by
the same amounts?, etc). Does zero degrees C result in zero pressure? What temperature in
degrees C would result in zero pressure?
11. Linear relationships result in a 1 to 1 increase or decrease ratio. Based on this is your graph of
pressure and temperature in degrees C linear?
12. It is now your job to determine the equation for the graph you have created. Use methods you
used in parts 1 and 2 to do this, using whatever method is most appropriate.
13. Check with your instructor