Squeeze a gas at constant temperature and its pressure rises just as fast as its volume falls: P × V stays constant. Shrink the volume and watch P2 = P1V1 ÷ V2 climb the hyperbola while the product PV holds steady.
Pressure P = P1V1 ÷ V
100 kPa
gauge = -1 kPa
Volume V2.00 L
Initial pressure P1100 kPa
Initial volume V12.00 L
Constant product P × V
P × V200 kPa·L
Ratio V / V11.00
volume × 1.00 of V1, so pressure × 1.00 of P1
Temperature T = 300 K, held constant · atmospheric = 101 kPa · pressures are absolute
Tip: halve the volume and the pressure doubles exactly — the product P × V never moves.