London Dispersion Forces

London dispersion animation:

Propane vs Butane vs Pentane and boiling point

http://chemsite.lsrhs.net/bonding/LondonDispersion.html

The strength of London dispersion binding forces is also dependent on molecular shape, because the shape affects the number of sites available for interaction between the atoms.

http://chemsite.lsrhs.net/bonding/shapeAndStrength.html

A compendium of animations of molecular attractions can be found at:

http://www.concord.org/%7Ebarbara/workbench_web/models/jnlps/newWeakForces1.jnlp