Physical Properties Alcohol

Boiling Points

  1. The boiling point of an alcohol is always much higher than that of the alkane with the same number of carbon atoms.
  2. 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.
  3. The boiling points of the alcohols increase as the number of carbon atoms increases.
  4. This can be explained by the folloowing:
    1. number of carbon increases, size of the molecule increases.
    2. intermolecular force increases.
    3. more heat energy is needed to overcome the intermolecular force.

Solubility of Alcohols in Water


  1. The small alcohols are completely soluble in water.
  2. However, solubility falls as the length of the hydrocarbon chain in the alcohol increases.
  3. Explanation:
    1. 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.
    2. In short chain alcohol, the hydroxyl group plays a major part in forming forces (hydrogen bond) in between water and alcohol molecule, therefore they are soluble in water.
    3. For the long chain alcohol, the hydroxyl group is just a small part of the molecule. Therefore, the insoluble long hydrocarbon chain contribute more to the forces in between water and alcohol molecule, causes the solubility

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