Fractional Distillation | Organic Chemistry | Chemistry | FuseSchool

Learn that crude oil is an unprocessed mixture of hydrocarbons with varying chain lengths extracted from land or sea. Understand that crude oil in its raw form is viscous and dark, requiring separation to be useful as fuels and chemicals.

Recognize that short-chain hydrocarbons have weaker intermolecular forces and lower boiling points, while long-chain molecules have stronger intermolecular forces and higher boiling points. This principle forms the basis for separation by fractional distillation.

Heat crude oil to a high temperature outside the column to vaporize most of it, then pump the hot vapor into the fractionating column which has a temperature gradient that is hottest at the bottom.

Allow long-chain hydrocarbons with high boiling points to condense back into liquid at the bottom of the column where temperatures remain high, and collect these as the first fraction.

Allow remaining vapor molecules to rise through the column and pass through bubble cap trays that slow their progression. The vapors gradually condense as they encounter progressively cooler temperatures at higher levels.

Collect small-chain hydrocarbons with low boiling points in trays near the top of the column where temperatures are coolest, separating them from heavier fractions.

Recognize that hydrocarbons collected in each tray are mixtures with similar boiling points called fractions, including petrol, naphtha, kerosene, diesel oil, and bitumen, each with specific industrial and fuel applications.