At constant pressure a gas expands as it warms: V ÷ T = k, a straight line through the origin. Move the sliders and watch V2 = V1 · T2 ÷ T1 while the constant k stays identical for both states.
Final volume V2 = V1·T2÷T1
4.00 L
volume change Δ = +100.0%
Initial volume V12.00 L
Initial temperature T1300 K
Final temperature T2600 K
Constant k = V ÷ T
State 1 (V1,T1)
0.006667 L/K
State 2 (V2,T2)
0.006667 L/K
identical at every temperature — that is Charles's law
Pressure held constant · the weighted piston floats freely · V is proportional to T with T in kelvin (never Celsius)
Tip: double T2 and the volume doubles; the two k values never drift apart, even as the line steepens.