Boyle's law – isothermal gas compression
PhysicsThermal Physics & GasesAges 17–18Virtual lab
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Thermal Physics & Gases
Pull or push a piston in a sealed cylinder at constant temperature. The measured pressure always satisfies p·V = constant; the p–V graph is a hyperbola while p–(1/V) is a straight line through the origin, exactly how Boyle's law is identified from experimental data.
Lesson: Boyle's law
What it shows
Boyle's law states that for a fixed mass of gas at constant temperature, pressure is inversely proportional to volume, so p·V stays constant. In the particle model, squeezing the gas into a smaller volume makes the molecules strike each unit area of the container walls more often, which raises the pressure. On a p–V graph an isothermal process is a hyperbola, which is hard to test by eye; plotting p against 1/V instead gives a straight line through the origin, the standard way to confirm inverse proportionality from experimental data.
How to use
Set Initial volume and Initial pressure, then drag the piston or move the Current volume slider to compress and expand the gas. At several volumes press Record data and check the p·V column in the table. Halve the volume and compare the new pressure with the starting value. Use the p against 1/V graph to test whether your points lie on a straight line through the origin, then repeat with a different initial pressure.
Parameters you can change
- Initial volume 0.5–6 L
- Initial pressure 0.5–3 atm
- Current volume 0.5–6 L
- Also show p vs 1/V graph
Questions to explore
- Why does the graph of p against 1/V give a straight line through the origin?
- If the initial pressure is doubled at the same initial volume, how does the p–V curve change?
- Which quantities must stay constant for the measured values to obey Boyle's law?
