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Volume
40 mL
Pressure
125 kPa
P × V
5000 kPa·mL
Temperature
300 K
How to use: The cylinder holds a fixed amount of gas at a constant
temperature, so only two things can change: volume and pressure. Drag the piston in —
the same gas squeezed into a smaller space bumps the walls harder, and the pressure
readout climbs. Pull it out and the pressure drops. Watch the moving point trace the
curve on the graph.
Notice: halving the volume doubles the pressure — that's the whole of Boyle's law,
P × V = a constant. Look at the readout: no matter where the piston sits, the product
P × V stays the same because the temperature hasn't moved. It's why a sealed aerosol can
in a fire explodes and why divers rising too fast get the bends.