An isomer with a branched structure will require: more energy to melt than the straight chain structure a higher temperature to boil than the straight chain structure less energy to melt than the straight chain structure the same energy to boil as the straight chain structure

The branched chain compounds have lower melting and boiling points as compared to straight chain isomers.This is due to the fact that branching  makes the molecule more compact. This results in decreases in surface area of isomer. But, the intermolecular attractive forces depends on the surface area of compound. Thus, branched isomers have lower intermolecular force of interaction, as compared to straight chain isomers. Consequently, the melting/boiling points of the branched chain isomers are lower as compared to  straight chain isomers.