Physical Properties Alcohol
- The boiling point of alcohol is always much higher than that of the alkane with the same number of carbon atoms.
- This is because, the presence of the hydroxyl group gives extra force between the molecules, hence more heat energy is needed to overcome the intermolecular force when boiling.
- The boiling points of the alcohols increase as the number of carbon atoms increases.
- This can be explained by the following:
- the number of carbon increases, the size of the molecule increases.
- intermolecular force increases.
- more heat energy is needed to overcome the intermolecular force.
The solubility of Alcohols in Water
- The small alcohols are entirely soluble in water.
- However, solubility falls as the length of the hydrocarbon chain in the alcohol increases.
- Every alcohol consists of two parts, the hydrocarbon chain which is not soluble in water, and the hydroxyl functional group, which is soluble in water.
- In short-chain alcohol, the hydroxyl group plays a significant part in forming forces (hydrogen bond) in between water and alcohol molecule, therefore they are soluble in water.
- For the long-chain alcohol, the hydroxyl group is just a small part of the molecule. Therefore, the insoluble long hydrocarbon chain contributes more to the forces between water and alcohol molecule, causes the solubility to decrease.