Why do intermolecular forces weaken as kinetic energy of particles increases?
Because intermolecular attraction is inversely proportional to distance between the molecules.
The molecules of matter at ordinary temperatures can be always be considered to be in ceaseless, random motion at high speeds. This implies that kinetic energy is associated with each molecule.
From the Boltzmann distribution we can deduce average Molecular Kinetic Energy associated with three dimensions of a molecule as
We also know that Intermolecular forces are forces of attraction or of repulsion which act between neighboring particles; which could be atoms, molecules, or ions.
Also that the force of intermolecular attraction is inversely proportional to distance between the particles.
The increased average kinetic energy keeps the molecules farther apart and moving around. This results in the increase of the average intermolecular distance. As mentioned above, the intermolecular attraction decreases.