Why does butane have a higher boiling point than propane?

Answer 1

The molecule of Methane is CH4; 1 carbon and 4 hydrogen atoms Butane's molecule C4H10 has 4 Carbon atoms and 10 hydrogen. So Butane has more parts to burn (connect to oxygen/oxidise) per molecule, hence a higher calorific value.

Answer 2

The M.P. and B.P. of any substance is related to the intermolecular forces that act.

Butane, which is a saturated hydrocarbon with 4 Carbon atoms, is heavier than Propane, which has only 3 Carbon atoms. Because of this, Butane has stronger Van der Waals forces (or London forces) than Propane. This means that it requires more energy to overcome the intermolecular forces in Butane, resulting in the relatively higher M.P. and B.P.

Note that the London forces are the only forces that act as intermolecular forces in the case of Butane and Propane.

Answer 3

The geometric structure of butane allows closer packing between molecules than can be achieved with 2-methylpropane, increasing the total van der Waal's forces in the butane solid and raising its melting point compared with that of 2-methylpropane.

Answer 4

Both are isomers. As branching increases (as in 2-methylpropane) the intermolecular force of attraction decreases, and hence melting point decreases.

Answer 5

This is because butanes chain length is longer than propanes making it harder to reach its boiling point