1. Define the following terms:
   1.1 homologous series
   1.2 functional group
   (2)
2. Write down the structural formula of the functional group for the following homologous series:
   2.1 alcohols
   2.2 aldehydes
   (2)
   2.3 carboxylic acids
   (2)
   2.4 ketones
   (2)
   (2)
   [14]

Homologous series refers to a group of organic compounds that share a similar functional group and have a identical general formula, but differ in the number of carbon atoms. This means each consecutive compound in the series has an additional CH₂ group, leading to a gradual change in their physical properties, like boiling point and solubility, while maintaining similar chemical properties.

Functional groups are specific atoms or groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They are key to understanding organic chemistry as they determine how compounds interact with each other. For example, the hydroxyl group (-OH) in alcohols gives these compounds their unique properties, making them distinct from other classes like carboxylic acids, which contain the carboxyl group (-COOH).

Structural formulas for the functional groups:
2.1 Alcohols: -OH
2.2 Aldehydes: -CHO
2.3 Carboxylic Acids: -COOH
2.4 Ketones: -C(=O)-