Gravity!
Dispersion forces (London dispersion forces) are generally the weakest type of intermolecular force. These forces are caused by temporary fluctuations in electron distribution around atoms or molecules, leading to weak attractions between them.
There are only four ways that substances interact, or if you prefer, four forces in the universe. They are gravity, the weak nuclear force, electro-magnetic, and the strong nuclear force. In molecules ( presumably in liquid or gaseous states ) they will be slightly pulled together by gravity, but it is the electro-magnetic force that governs everything else. Whether they bind together, break down into component atoms or simpler molecules, form new compunds, etc. is all part of the electro-magnetic interaction.
intermolecular force
This is an intermolecular force.
Boiling point is a property not a force; but a high boiling point indicate a strong intermolecular force.
Intermolecular attraction
The attractive force between masses is known as gravity. It is responsible for keeping planets in orbit around stars and objects on Earth grounded.
The intermolecular force in Ar (argon) is London dispersion forces, which are the weakest type of intermolecular force. This force is caused by temporary fluctuations in electron distribution around the atom, leading to temporary dipoles.
Intramolecular forces are not intermolecular forces !
The intermolecular force in BF3 is London dispersion forces. This is because BF3 is a nonpolar molecule, so the only intermolecular force it experiences is the temporary weak attraction between temporary dipoles.
Intermolecular forces shown by the dotted lines not by strong covalent bonds.