greater intermolecular forces and low vapour pressure
Explanation:
imagine a chain consisting of 15 carbons and another consisting of 5 carbons. it will require much force to separate the bonds present between the 15 chained carbon molecule than the 5 chained carbon molecule. with larger carbon chains means a larger surface area possible for hydrophobic interaction and thus a higher boiling point .
We must slso keep in mind that vapour pressure is indirectly proportional to molecular forces. This means that the greater the intermolecular forces the lower the vapour pressure.
