What factors affect the boiling point of hydrocarbons?

As the hydrocarbon chain length increases, their are more intermolecular forces between the chains. This means more energy is needed to pull the chains apart so boiling points increase as the size of the hydrocarbons increase. Alkenes are also hydrocarbons and the presence of double bonds can also affect boiling points as "trans" double bonds pack more closely together than "cis" double bonds so have higher melting points. Trans fats are usually solids at room temperature and are associated with a greater risk of cardiovascular disease. At A level we also have to consider the shape of the hydrocarbons, for example whether they are branched, as this can reduce the boiling point compared to a straight chain molecule..