(a) What are hydrocarbons ? Give examples.
(b) Give the structural differences between saturated and unsaturated hydrocarbons with two examples each.
(c ) What is functional group ? Examples of four different functional groups.

Explanation

(a) The compounds that are made up of carbon and hydrogen atoms are called hydrocarbons. E.g., methane `(CH_(4))`, ethene `(CH_(2)=CH_(2))`. Ethyne `(C_(2)H_(2))`, cyclohexane `(C_(6)H_(12))`, benzene `(C_(6)H_(6))` etc.
In saturated hydrocarbons, all the four valencies of carbon are satisfied by a single covalent bonds while in unsaturated hydrocarbons, double or triple bonds are required to satisfy the valencies. e.g.,
(i) Saturated hydrocarbons
Methane `(CH_(4))` , Ethane `(CH_(3)-CH_(3))`
(ii) Unsaturated hydrocarbons
Ethene `(H_(2)C=CH_(2))` , Ethyne `(CH-=CH)`
(c ) A functional group is atom or group of atoms that defines the structure (or the properties) of organic compounds. The four examples are
`{:((i),-OH,,,,"Alcohol"),((ii),-COOH,,,,"Carboxylic acid"),((iii),-CHO,,,,"Aldehyde"),((iv),-X,,,,"Halogens"):}`