Question

If you squash a balloon, the pressure inside it rises. How does the kinetic theory explain this?

Answer 1

Pressure can be defined in terms of the particle model (kinetic molecular theory) as being the number of collisions per unit time of the particles.

So if you squash a balloon, you decrease its volume. The same number of particles are present inside the balloon as before, but they now have less space in which to move so they will collide more frequently with each other, hence resulting in the pressure to increase.