# CHM 101 Boyles Law Lab Pressure Volume Relationship in Gases Project

Revised 6/15/17CHM101 – Boyle’s Law: Pressure-Volume

Relationship in Gases

The primary objective of this experiment is to determine the relationship between the pressure

and volume of a confined gas. The gas we use will be air, and it will be confined in a syringe

connected to a Gas Pressure Sensor (see Figure 1). When the volume of the syringe is changed

by moving the piston, a change occurs in the pressure exerted by the confined gas. This pressure

change will be monitored using a Gas Pressure Sensor. It is assumed that temperature will be

constant throughout the experiment. Pressure and volume data pairs will be collected during this

experiment and then analyzed. From the data and graph, you should be able to determine what

kind of mathematical relationship exists between the pressure and volume of the confined gas.

Historically, this relationship was first established by Robert Boyle in 1662 and has since been

known as Boyle’s law.

OBJECTIVES

In this experiment, you will

• Use a Gas Pressure Sensor and a gas syringe to measure the pressure of an air sample at

several different volumes.

• Determine the relationship between pressure and volume of the gas.

• Describe the relationship between gas pressure and volume in a mathematical equation.

• Use the results to predict the pressure at other volumes.

Figure 1

MATERIALS

LabQuest

LabQuest App

Vernier Gas Pressure Sensor

20 mL gas syringe

PROCEDURE

1. Prepare the Gas Pressure Sensor for data collection by

a. Connect the Gas Pressure Sensor to CH 1 of the LabQuest and choose New from the File

menu. You should see a reading for Ch 1 Pressure on the meter screen.

b. With the 20 mL syringe disconnected from the Gas Pressure Sensor, move the piston of

the syringe until the front edge of the inside black ring (indicated by the arrow in Figure 1)

is positioned at the 10.0 mL mark.

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Revised 6/15/17

c. Attach the 20 mL syringe to the valve of the Gas Pressure Sensor with a clock-wise twist.

Do not over tighten the plastic connection or it may crack. Now there is a constant number

of molecules of air trapped inside the syringe and gas pressure sensor. From this point

forward do not remove the syringe from the pressure sensor. Simply slide the piston of

the syringe in or out to achieve the desired volume settings.

2. Set up the data-collection mode by

a. On the Meter screen, tap Mode. Change the mode to Events with Entry.

b. Enter the Name as Volume and Units as mL. Select OK.

3. Look at the syringe; its scale reports its own internal volume. However, there is a little bit of

space inside the pressure sensor, about 0.8 mL. As you proceed, you will need to add 0.8 mL

to the syringe volume settings to get the accurate total volume of the system. For example:

the syringe volume reads 5.0 mL, you will need to enter 5.8 mL as the value for the total

volume.

4. Collect pressure and volume data by

a. Tap the start button (green triangle) to start data collection.

b. Push in the piston until the front edge of the inside black ring (see Figure 2) is positioned

at the 5.0 mL line on the syringe. Hold the piston firmly in this position. Tap Keep (you

may now release the piston) and enter 5.8 as the total gas volume (in mL) on the screen.

Select OK to store this pressure-volume data pair.

Figure 2

c. Adjust the piston until the front edge of the inside black ring is positioned at the 7.0 mL

line on the syringe. Hold the piston firmly in this position. Tap Keep then enter 7.8 mL as

the total gas volume (in mL) on the screen. Select OK.

d. Repeat the process for the following volumes: 9.0 mL, 11.0 mL, 13.0 mL, 15.0 mL, 17.0

mL, and 19.0 mL. Remember to add 0.8 mL to the recorded volumes.

e. Tap the stop button (red square) to stop data collection.

5. A graph of pressure vs. volume will be displayed. Tap the Data Table icon and record the

pressure and volume data values in your data table.

6. To confirm that an inverse relationship exists between pressure and volume, a graph of

pressure vs. reciprocal of volume (1/volume) is plotted. To do this using LabQuest:

a. Tap the Data Table icon to display the data table.

b. Tap Table menu and choose New Calculated Column.

c. Enter the Name (1/Volume) and Units (1/mL). Select the equation, A/X. Use Volume as

the Column for X, and 1 as the value for A.

d. Select OK.

7. Follow this procedure to calculate regression statistics and to plot a best-fit regression line on

your graph of pressure vs. 1/volume:

a. Tap the Graph icon.

b. Tap Graph from the menu tab.

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Revised 6/15/17

c. Select Autoscale from 0 and select OK.

d. Tap Analyze from the menu tab. Choose Curve Fit from the Analyze menu. Choose

“Pressure.”

e. From the Fit Equation drop down menu, choose “Linear”.

f. The linear-regression statistics for these two data columns are displayed in the form:

y = mx + b

where x is 1/volume, y is pressure, m is a proportionality constant, and b is the y-intercept.

g. Select OK. If the relationship between P and V is an inverse relationship, the graph of

pressure vs. 1/volume should be direct; that is, the curve should be linear and pass through

(or near) the origin. Examine your graph to see if this is true for your data.

8. Save Graph

1. Plug your USB into the LabQuest and save the graph in LabQuest.

2. Click on File tab, choose Print → select Graph.

3. In the dropdown box, select Print to file (PDF). Check the box where it says Print graph

Title, then enter the graph title.

4. Tap Print. The graph should be saved in your USB.

5. Print out the graph and attach it to your lab report.

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Revised 6/19/17

Name __________________________Station # _______ Date _________________

CHM 101 – Boyle’s Law

Pre-Lab Questions

1. Describe in words the relationship between pressure and volume at a constant

temperature.

2. Describe the relationship between gas pressure and volume in a mathematical equation.

3. Which of the following graphs (A,B,C,D) correctly represents the relationship between

the pressure and the volume of an ideal gas that is held at constant temperature?

4. A balloon with a volume of 2.0 L is filled with a gas at 3 atmospheres. If the pressure is

reduced to 0.5 atmospheres without a change in temperature, what would be the volume

of the balloon?

Hint: Use P i V i = P f V f where

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Revised 6/19/17

P i = initial pressure

V i = initial volume

P f = final pressure

V f = final volume

To find the final volume, solve the equation for V f

5. The volume of the lungs is measured by the volume of air inhaled or exhaled. If the

volume of the lungs is 2.400 L during exhalation and the pressure is 101.70 KPa, and the

pressure during inhalation is 101.01 KPa, what is the volume of the lungs during

inhalation?

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Revised 6/29/17

Name __________________________Station # _______ Date _________________

CHM 101 – Boyle’s Law

Report Sheet

DATA AND CALCULATIONS

Volume

(mL)

1/Volume (1/mL)

Pressure

(kPa)

Constant, k

(P • V)

Make an Excel graph Pressure vs. 1/Volume Excel and attach it to your report.

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Boyle’s Law

Make-Up Data

Instructions:

Use the following data to complete the data /calculation sheet of the experiment. Write your

weekly lab report for this lab, using this data and following the lab syllabus instructions

DATA AND CALCULATIONS

Volume

(mL)

Pressure

(kPa)

1/Volume (1/mL)

5.8

197.65

7.80

143.98

9.80

111.98

11.80

93.97

13.80

78.86

15.80

69.37

17.80

61.82

19.80

55.62

Constant, k

(P • V)

Revised 6/19/17

Name __________________________Station # _______ Date _________________

CHM 101 – Boyle’s Law

Post Lab Questions

1. If the volume is doubled from 5.0 mL to 10.0 mL, what does your data show happens to

the pressure? Show the pressure values in your answer.

2. If the volume is halved from 20.0 mL to 10.0 mL, what does your data show happens to

the pressure? Show the pressure values in your answer.

3. If the volume is tripled from 5.0 mL to 15.0 mL, what does your data show happened to

the pressure? Show the pressure values in your answer.

4. From your answers to the first three questions and the shape of the curve in the plot of

pressure versus 1/volume, do you think the relationship between the pressure and volume

of a confined gas is direct or inverse? Explain your answer.

5. Based on your data, what would you expect the pressure to be if the volume of the

syringe was increased to 40.0 mL. Explain or show work to support your answer.

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Revised 6/19/17

6. Based on your data, what would you expect the pressure to be if the volume of the

syringe was decreased to 2.5 mL.

7. What experimental factors are assumed to be constant in this experiment?

8. How constant were the values for k you obtained in your data table? Good data may show

some minor variation, but the values for k should be relatively constant.

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