14. ALCOHOLS

Question 1

Explain the difference in physical properties between alcohols and alkanes

Answer 1

Alkanes have non-polar bonds due to the similar electronegativity of the carbon and hydrogen atoms.
Therefore alkanes are non-polar.
The intermolecular forces between non-polar molecules are very weak london forces.

Alcohols contain polar O-H bonds due to the difference in electronegativity between the oxygen and hydrogen atoms.
Therefore alcohols are polar.
The intermolecular forces are weak London forces, however there will also be much stronger hydrogen bonds between the polar O-H groups.

Question 2

Compare volatility between alcohols and alkanes
incl brief explanation

Answer 2

Alcohols are less volatile than alkanes.
Both alcohols and alkanes contain weak London forces, however alcohols also contain strong hydrogen bonds between the polar O-H groups.
These strong hydrogen bonds require more energy to overcome.

Question 3

Compare melting point in alcohols and alkanes.
incl brief explanation

Answer 3

Alcohols have higher melting points than alkanes.
Both alcohols and alkanes contain weak London forces, however alcohols also contain strong hydrogen bonds between the polar O-H groups.
These strong hydrogen bonds require more energy to overcome.

Question 4

Compare water solubility between alcohols and alkanes.
incl brief explanation

Answer 4

Alcohols have greater water solubility than alkanes.
Alcohols can form strong hydrogen bonds with water, alkanes cannot.