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My question is

Why has methane a lower boiling point than octane???

Methane has 1 carbon and Octane has 8 carbons. The octane molecule is longer and so there is more surface contact and so more London forces between molecules in octane compared to methane. More London forces requires a greater amount of energy to overcome (heat energy) hence a higher boiling point for octane and lower boiling point for methane

(edited 5 years ago)

Reply 2

Namikaz3

Bro, all that depends on the chain length of that hydro-carbon.
Methane has only one carbon atom where as octane has 8 carbon.As the number of carbon atoms increase the chain length increases.So when the chain length increases the intermolecular attractions between molecules increases so the energy requires to break that force attractions become high.Because of that the larger molecular chain of hydrocarbon (octane) has a higher boiling point than the small chained methane. JUST always remember that when ever the size of the molecule increases the boiling point increases in terms of energy requires to break the attractions.They break molecular forces but not atomic bonds!!
Good luck!!