Why does a substance dissolve, using the kinetic theory of matter?

Answer 1

Some substances do NOT dissolve in a liquid. But those that do, do so because of Brownian motion in the liquid, which is the constant vibration and movement of molecules. This causes a sort of molecular bombardment which eventually dissolves or erodes the static molecules or atoms in the substance.

Answer 2

Particles are in constant motion, sooner or later they will find a 'spot' to 'dissolve' all by them selves.

Or, you could stir, shake, or heat, speeding it all up, but no need you have the kinetic Theory of Matter.