1. Fractional distillation of petroleum is used because the petroleum fractions have different boiling points

2. Hydrocarbon compounds: organic carbon componds made up of only carbon and hydrogen elements

• Saturated hydrocarbons have single covalent bonds between carbon atoms
• Unsaturated hydrocarbons have at least one double covalent bond or triple covalent bond between carbon atoms

3. Homologous series is made up of a specific group of organic compounds which have similar chemical properties