Why do intermolecular forces increase with the size of the molecules/atoms?

Even if the atoms are the same size, bigger molecules have stronger London dispersion forces. There are more electron clouds to distort. The hydrocarbons from methane to pentane contain only C and H atoms. As the chains get longer and snuggle up close to each other, there are more contact points between them.

a pan containing water is placed in a positio n where it is exposed to a 10 mile per hour wind. the pan contains a uniform depth of 1.27 cm of water, is quite wide, and has a length of 2.44 m in the wind direction. the water in the pan is at a constant temperature of 15.5 °c.