Edexcel A-Level Physics Absolute Zero and Molecular Kinetic Energy

Indicative content:

- As the temperature of the air decreases, the mean kinetic energy of the molecules decreases.
- Therefore the root mean square speed decreases; equivalently, since $E_k=p^2/(2m)$, the average momentum of the molecules decreases.
- The change of momentum of a molecule during a collision with the container wall decreases.
- The rate of collisions with the wall also decreases.
- Hence the rate of change of momentum, and therefore the force on the wall, decreases.
- The pressure exerted by the gas decreases because p=F/A.

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