Surface tension is defined as the tendency of elasticity of a liquid surface that makes it to achieve the possible least surface area. It depends upon the intermolecular forces present on the boundary of the surface of the compound and its contact.
n-butane [tex](CH_{3}CH_{2}CH_{2}CH_{3})[/tex] is non-polar compound and it consist of only weak dispersion forces that are responsible for any contact with the surface.
In comparison to other given substances, n-butane has the weakest dispersion forces. Thus, n-butane has lowest surface tension.
