Equipment required Boyle’s law apparatus, air pump
Method
1. Set up apparatus as shown in M1.5a, by connecting the air pump to the Boyle’s law apparatus. 2. Make sure the gas volume is at atmospheric pressure at the beginning by opening and closing the tap.
NOTE
3. Pump air into the apparatus until the pressure gauge (Bourdon gauge) reaches its maximum safe pressure.
4. Wait a few minutes for the oil level to stabilise. 5. Take the pressure reading from the gauge. 6. Take the corresponding gas volume reading from the tube. 7. Gradually open the tap to release some of the air and close again. 8. Repeat steps 3–7 at least five more times and record the results in your table, for pressure and volume, until atmospheric pressure is reached again.
9. Plot a graph of P against 1/V on graph paper, drawing a best fit line through the points.
Pressure (atms or Pa) Volume (cm3) 1/Volume Characteristic graph PV
Record the volume level of the gas at the top of the scale and not the volume of oil at the bottom.
NOTE
Only release enough air so as you will be able to take at least 5–6 readings as you progress.
1 / Volume M1.5b Result
• You should have gained correct values for p and V, in order to draw a reasonably straight line through the origin. (Make sure to use appropriate units.)
• Your values of PV should all be approximately the same in your table. This verifies the proportional- ity: as one value increases, the other decreases proportionally.)
Conclusion
Pressure is inversely proportional to volume at constant temperature.
Errors
The following errors should be considered when studying this experiment:
• hysteresis in measurements (this is the delay in a variable property of a system with respect to the effect producing it)
• temperature of oil, due to friction • parallax of length measurement and/or meniscus level
• temperature variations in the room • oil leakage.
