What causes dispersion forces?
Disperson forces are caused by an unsymettrical distribution of charge in the molecule, causing a net electric force.
http://www.chem.purdue.edu/gchelp/liquids/disperse.html
To understand what causes dispersion forces, we need to understand the concept of electron cloud distribution in molecules.
In a molecule, the electrons are constantly moving and can be found in different regions around the nucleus. This movement creates temporary shifts in electron density within the molecule.
Dispersion forces, also known as London dispersion forces, arise from the temporary fluctuations in electron distribution. These fluctuations cause an unsymmetrical distribution of charge within a molecule, resulting in the formation of temporary dipoles.
The temporary dipoles in neighboring molecules then induce the formation of additional dipoles. This causes the molecules to attract each other, resulting in dispersion forces.
So, in summary, dispersion forces are caused by the unsymmetrical distribution of charge in a molecule due to temporary fluctuations in electron distribution.