Part 1: Boyle’s Law: Pressure–vs–Volume

The objective of this experiment is to re-examine the relationship between the pressure and volume of a confined gas using available technology. The gas we use will be air, and it will be confined in a syringe connected to a 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 Pressure Sensor. Temperature is assumed to be constant throughout the experiment. Pressure and volume data pairs will be collected and then analyzed. From the data and graph, you should be able to determine the mathematical relationship between the pressure and volume of the confined gas. This relationship was first established by Robert Boyle in 1662 and has since been known as Boyle’s law.

Figure 1

MATERIALS

CBL 2 interface / ChemBio Program
TI Graphing Calculator / 20-mL gas syringe
Vernier Gas Pressure Sensor

PROCEDURE

  1. Position the plunger at the 20-mL mark of the syringe and connect to the Pressure Sensor as shown in Figure 1.
  2. Connect the pressure gauge to channel 1 (CH1) of the CBL 2 interface.
  3. Connect the CBL 2 to your TI 83 calculator. Make sure all connections are snug.
  4. Hit the APPS Button on your calculator, and using the arrow keys, scroll down until you find the ChemBio program. Hit ENTER.
  5. When you get to the ***MAIN MENU***, choose #1: SET UP PROBES. Follow the prompts on the screen. See Figure 2.
  6. At the **CALIBRATION** screen, choose #1: USE STORED.
  7. At the PRESSURE screen, choose #1: GAS PRESSURE
  8. Choose your desired units of pressure, kPa, Atm, or mm Hg. Hit ENTER.
  9. You are now ready to collect data. Choose #2: COLLECT DATA.
  10. At the DATA COLLECTION screen, choose #3: TRIGGER/PROMPT
  11. The next steps will require some coordination between you and your lab partner. While one person is manipulating the plunger, your partner should be in charge of hitting the [+] key to collect the data. This may take a little practice. Don’t fret if you don’t get it all the first time.
  12. Collect as many data points as possible. Your first data point (pressure reading) will be for 20 ml (original position of plunger).
  13. When you receive the prompt ENTER VALUE ? Type in the volume from the syringe. So, your first entry will be 20, to indicate the pressure the CBL 2 recorded was for a volume of 20 ml.
  14. At each subsequent DATA COLLECTION screen, choose #1: MORE DATA until you are finished with the experiment, at which point you will choose #2: STOP.
  15. Hit the ENTER key to return to the ***MAIN MENU***. From here you can view your graph, fit a curve to the data, and view the data.
  16. Proceed to the Extension and re-analyze your data following the provided instructions.

DATA AND CALCULATIONS

Tabulate and graph pressure vs. volume data and record the equation fitting your data.

Your data is stored in L1 and L2 which can be accessed by hitting the STAT button and then EDIT.

You can “connect the data points” by changing the plot type in the STAT PLOT menu.

Answer each of the following lab questions in your lab notebook, Be sure to show all work, and follow appropriate graphing rules (labeled axes, titles, etc.)

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 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.

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.One way to determine if a relationship is inverse or direct is to find a proportionality constant, k, from the data. If this relationship is direct, k = P/V. If it is inverse, k = P•V. Based on your answer to Question 4, choose one of these formulas and calculate k for the seven ordered pairs in your data table (divide or multiply the P and V values). Show the answers in the third column of the Data and Calculations table.

9.How constant were the values for k you obtained in Question 8? Good data may show some minor variation, but the values for k should be relatively constant.

10.Using P, V, and k, write an equation representing Boyle’s law. Write a verbal statement that correctly expresses Boyle’s law.