Boiling points of v. similar organic molecules
Solids and liquids are hold together by cohesion. Intermolecular interactions contributing to cohesion depend on the geometry of the molecules in interaction,too.  Here, n-pentane with an elongated molecular structure exhibits a much larger molecular surface as compared to neo-pentane of a more sphere-like structure*).  As a result, other criteria kept constant (like the molecular mass), the lesser the molecular surface area of molecules of a substance, the lower the boiling temperature of this substance.

*)True, neo-pentane's methyl groups point towards the vertices of a tetrahedron. Actually I recommend to build a molecular model of both compounds and place them side-by-side to see it.