Verification of Boyle’s Law using a computer

 

Using the supplied software, it is found that calculated values of PV are not constant, and the graph does not go through the origin.  Therefore these results do not support Boyle’s law.  However, the values of Volume recorded are only the volumes of air in the syringe.  No allowance has been made for the air in the connection to the sensor, or in the gas pressure sensor itself.  A correction of the order of 0.7 cm3 added to each volume improves matters considerably.  The true volume of air is the syringe reading added to approximately 0.7 cm3.  It is possible to create a file which allows for this, and which can be saved to provide a ready-made template for the experiment.

 

Setting up the software for Boyle’s law

 

1.      Start the logger program.

2.      In the File menu click on Open.

3.      In the pop-up window, double click on the folder Chemistry with Computers.

4.      In the new window double click on Exp 06 Boyle’s Law.

5.      In the next pop-up window select Gas Pressure Sensor and click on Open.

6.      The Graph Window now has appropriate labels and the correct sampling mode has been set.

 

To create a column for Syringe Reading

1.        Click on Data in the menu bar.

2.        In the drop-down menu select Column Options, then select Volume.

3.        In the pop-up window type Syringe Reading as the Long Name.

4.        Complete the fields as appropriate.

5.        Click OK.

 

To create a column for Volume

1.        Click on Data in the menu bar.

2.        In the drop-down menu select New Column, then select Formula.

3.        In the pop-up window  complete the fields (Volume, V, cm^3).

4.        Click the Definition tab. In the Equation field type  0.7 +   .

5.        In the Variables field click the down arrow, select Syringe Reading and click OK.

6.      The column Volume immediately appears in the data table window.

 

To create a column for 1/V

1.        Click on Data in the menu bar.

2.        In the drop-down menu select New Column, Formula.

3.        In the pop-up window  complete the fields (Inverse Volume, 1/V,   cm^-3).

4.        Click the Definition tab. In the Equation field type 1/V.

5.        In the Variables field click the down arrow, select Volume and click OK.

6.      The column 1/V immediately appears in the data table window.

 

To create a column for PV

1.      Click on Data in the menu bar.

2.      From the drop down menu select New Column and choose Formula.

3.        In the new window click on the Definition tab.

4.        Place the cursor in  the Equation field .

5.        In the Variables field click the down arrow, select Pressure, and type *

6.      In the Variables field click the down arrow, select Volume and click OK.

 

To save this file

1.      In the File menu click on Save As…

2.      In the pop-up window Save in Physics with Computers.

3.      Type in a name for the file, e.g. “Boyle’s Law Amended”.

4.      Click Save.

 

The experiment file is now saved in the computer and can be called up when required.

 

Arrangement

 

1.      Set the syringe to 10 cm3 and attach by screwing onto the gas pressure sensor.

2.      Attach the gas pressure sensor to CH 1 of the logger.

3.      Attach the logger to the computer.

4.      Start the computer logger program.

5.      In the File menu click on Open.

6.      In the pop-up window, double click on the folder Physics with Computers.

7.      In the new window double click on Boyle’s Law Amended.

8.      The Graph Window now has appropriate labels and the correct sampling mode has been set.

9.      If necessary, set the horizontal axis to volume and the vertical axis to pressure by clicking on the axes labels.

 

Procedure

 

1.      With the syringe set at 15 cm3 press  at the top of the screen.

2.      When the Pressure reading is stable press .

3.      In the pop-up window, enter 15 for volume and click OK.

4.      Change the syringe volume to 14 cm3 and repeat Steps 2 and 3, this time               entering 14 for the volume.

5.      Continue changing the syringe volume in 1cm3 decrements down to 5 cm3, collecting data as before.

6.      After the final data point press Stop  to end data collection.  A graph of P against V has been generated in the Graph Window.

Data Manipulation and Analysis

 

To generate a graph of P against 1/V

·        Click on the label of the horizontal axis

·        In the window click the button 1/V

 

To see the origin

·        Click on View in the menu bar.

·        In the menu select Graph Options and click on the Axis Options tab

·        Set both axes to Autoscale from 0

 

To draw a line of best fit

·        Click on Analyse in the menu bar

·        In the drop down menu select Linear Fit

 

A line of best fit appears in the graph window.  A floating box gives numerical details.

 

To view column for PV

Select the Table Window.  To see values of PV either maximise the window, or scroll to the right.

 

Sample Data

Syringe/cm3      Pressure/kPa    Volume/cm3      1/Volume/cm -3 PV/kPa cm3

15.00               72.00               15.85               0.06309                       1141

14.00               76.66               14.85               0.06734                       1138

13.00               82.33               13.85               0.07220                       1140

12.00               88.57               12.85               0.07782                       1138

11.00               95.72               11.85               0.08439                       1134

10.00               105.5               10.85               0.09217                       1144

9.000               115.3               9.850               0.1015                         1136

8.000               128.3               8.850               0.1130                         1135

7.000               144.9               7.850               0.1274                         1138

6.000               166.4               6.850               0.1460                         1140