why do dispersion forces exist between non-polar molecules?

Question

Please help me. I am at my wits end on how to answer this question.
Thanks in advance.

Answer 1

In any molecule, the electrons of the molecule are in motion sort of over the entire molecule. At any one particular instant, it is possible that the electrons will not be perfectly evenly distributed. That sets up a situation where the molecule is very slightly polar (has a part that is slightly negatively charged and another part that is slightly positively charged). That very short lived, transient dipole causes movement of the electrons in very nearby molecules. The result is that the molecules will be attracted to each other very slightly--a dispersion force.