Let us take Boyles law to start.
- Gas is perfect.
- In a massless piston that can be expanded with no friction
If we were to decrease the volume of the piston, the pressure inside would go up because the gas molecules would be hitting the sides more often.
If we were to increase the outside pressure on the piston, the volume of the piston would go down until the internal pressure matched the external pressure.
We see here that Boyle's law is perfectly explained by the kinetic model of gases (T held constant).
Let's look at Charles law (P held constant)
If we were to increase the temperature of the molecules, their kinetic energy would increase and would therefore hit the piston with greater force and increase the volume of the piston until the internal and external pressures are equal.
But if we were to spontaneously increase the volume of the piston, the temperature would NOT increase as a result (to maintain the increased volume against the constant external pressure) because heat doesn't spontaneously arise.
So it seems that Charles law only works one way, but not the other. And that T and V are not intrinsically linked like P and V are in Boyles law. Is this true?