Experiment 12 - An Investigation of Boyle’s Law
PRE-LABORATORY ASSIGNMENT
Name________________________________________
Section _________
1. Plot the pressure (Y-axis) vs. 1 / volume (X-axis) on graph paper. Once you have done that,
draw the best-fit line for the points you have plotted.
mL / Volume
0.0100
0.0111
0.0125
0.0143
0.0167
0.0200
Pressure/atm
0.254
0.282
0.319
0.362
0.423
0.511
2. From the above graph, determine the pressure in torr if the volume is 84.2 mL
3. Give the SI unit for pressure __________________________
4. Give the SI unit for volume _________________________
Experiment 12 - An Investigation of Boyle's Law
INTRODUCTION
Boyle's Law is a relationship between the pressure and volume of a gas. You will
measure the pressure of air in a syringe at different volumes. You also need to know the
volume in the tubing that connects the syringe to the pressure sensor. Let Vsyr be the
volume of the syringe, and “a” be the volume in the tubing. Recall, Boyle's Law states
(mathematically) that the volume multiplied by the pressure is a constant. So:
P (Vsyr + a) = k
12.1
the actual volume is the sum of the syringe volume and the volume in the tubing.
Multiplying out the left hand terms yields:
P Vsyr + P a = k
12.2
P Vsyr = − a P + k
12.3
Rearranging:
Equation 12.3 is in the form of a linear equation (y = mx + b). Plotting PVsyr on the Yaxis, and pressure on the X-axis yields a straight line with a slope equal to -a.
PROCEDURE
Part A - Computer Setup
1.
Attach the rectangular end of the gray cord to the back of the laptop computer and
the round end to the Science Workshop black box interface.
2.
Turn on the Pasco Scientific Workshop black box interface. You should see a green
LED on the front face of the interface.
3.
Turn on the computer. When the computer has booted-up, click on the "Start" icon
in the lower left corner. Select "Programs" on the pull-down menu, then select Data
Studio. Again select Data Studio. The program should start.
4.
On the opening screen, select “create experiment”.
5. Obtain a Pasco Scientific Absolute Pressure Sensor. Plug the DIN end of the Pasco
Scientific Absolute Pressure Sensor to Analog Channel "B" on the interface. Your
setup should look like the setup in Figure 12.1.
Figure 12.1
6. Click and drag the pressure sensor (absolute) on the screen up to Channel "B" on the
black box image on the screen.
7. Click and drag the table icon in the displays box to Channel B on the screen.
8. Double click on the "Options" box. You may need to move the "table" box in order to
see the sampling options box. Since you will be entering some data from the
keyboard, click the box next to the word "Keep data values only when commanded".
Under the name parameter, enter "Volume". In the box titled units, enter "mL".
Finally, click on the box titled “Include a list of prompted values for this keyboard
data”. Then click the OK to exit the box.
9. In the data window, click and drag the “Prompt Data” symbol in the Data window
onto the Table 1 window.
Part B - Doing the Experiment
1. Set the syringe to 10 mL. Attach the white connector on the syringe to the white
connector on the pressure sensor.
2. When you are ready to begin, click on "Start". Pull the syringe to 20.0 mL and hold
the syringe at that volume. Press the “Keep” button at the top of the DataStudio
screen. The computer will ask you for the volume. The partner types the volume
(20.0) on the keyboard, then presses "Enter". When "Enter" is pressed, the pressure
will be recorded.
3. Move the syringe to the next volume (18.0 mL), click on “Keep” when the syringe is
steady. Type the volume on the keyboard, then press "Enter".
4. Repeat using the following volumes: 16.0 mL, 14.0 mL, 12.0 mL, 10.0 mL, 8.0 mL,
7.0 mL, 6.5 mL, 6.0 mL, 5.5 mL, and finally, 5.0 mL. After all of these readings, you
should have 12 data points. Click on the red button beside the start button to end the
data collection.
Part C – Building the Graph
1. Determining “a”
a. In Microsoft Excel, put the pressures from Table 1 in one column and the pressure
x volume product from Table 1 in a adjacent column.
b. Highlight all of the numbers in both columns.
c. Using the Chart Wizard (colored bar icon) construct a XY (scatter) chart.
d. Title the chart (“Exp. 12 – Determination of “a” – (your name)”) and name the
axes of the graph.
e. Click on the button next to “As New Sheet”. Click on “Finish”.
f. From the chart, right click on any data point. Select “Add Trendline” from the pull
down menu.
g. Click on the “Options” tab. Click on the boxes marked “Display Equation on
Chart” and “Display R-squared Value on Chart”.
h. The equation for the best fit line will be displayed. The slope of the equation is
equal to -a.
2. Boyle’s Law
a. In Microsoft Excel, construct a table in which “1 / Corrected Volume” is in one
column and the pressure from Table 2 is in an adjacent column.
b. Highlight all of the numbers in both columns
c. Using the Chart Wizard (colored bar icon) construct a XY (scatter) chart.
d. Title the chart [“Exp. 12 – Boyle’s Law Plot – (your name)”] and label the axes of
the graph.
e. Click on the button next to “As New Sheet”. Click on “Finish”.
f. Right click on any data point. Select “Add Trendline” from the pull down menu.
g. Click on the “Options” tab. Click on the boxes marked “Display Equation on
Chart” and “Display R-squared Value on Chart”.
h. Under forecast, enter the following numbers:
Forward: 0 units. Backward: 0.05 units. Click on “OK”.
i. The equation for the best fit line will be displayed.
SAFETY
There are no extreme hazards in this experiment; however, appropriate eye protection
must be worn.
Experiment 12 - An Investigation of Boyle's Law
REPORT
Name________________________________________
Section _________
1) Determination of “a”
Table 1
Vsyr /mL
Pressure/kPa
Attach your plot of (PVsyr) versus P.
Value of “a” ______________________________ .
Pressure x Volume in mJ
2) Boyle’s Law
Table 2
Corrected Volume
(Vsyr + a)/ (mL)
mL / Corrected
Volume
Pressure/ kPa
Pressure x
Corrected Volume
in mJ
3) Average value of the PV product
[Be sure to include units]
__________________________
4) Standard Deviation of the PV product
[Be sure to include units]
___________________________
5) Attach your Boyle’s Law plot.
POST-LABORATORY QUESTIONS
1. From your average and standard deviation for pressure x volume, how many
significant figures should be reported for your average value?
2. List possible sources of error in this experiment.
3. Using your Boyle’s law graph, determine the pressure (in torr and atm) in the syringe
if the corrected volume of the syringe were 8.4 mL
(1atm = 760torr, 1atm = 760mm Hg, 1atm = 101,325Pa).
4. Verify that the PV product that you calculated has the units of mJ.