The trends in boiling and melting temperatures of alkanes with increasing chain length
- as chain length increases, boiling and melting temperatures increase
- van der Waals forces become larger with more points of contact
The effect of branching in the carbon chain on the boiling and melting temperature of alkanes
- as branching increases, boiling and melting temperature decreases
- side chains interfere with points of contact between atoms, so van der Waals forces are smaller
The relatively low volatility (high boiling point) of alcohols compared to alkanes with a similar number of electrons
- alcohols can form hydrogen bonds as well as van der Waals forces
The trends in boiling temperatures of the hydrogen halides HF to HI
- a gradual increase in boiling temperature from HF to HI would be expected, as the increasing atomic size means more van der Waals forces
- this is true for HBr to HI, but HCl and HF are different
- HCl has a more polar bond, so the permanent dipole-dipole interactions are stronger
- HF can form hydrogen bonds
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