Fractional Distillation | Organic Chemistry | Chemistry | FuseSchool

Introduction to Crude Oil and Fractional Distillation00:00:04

Crude oil is unprocessed oil from the ground, a valuable resource providing a great number of hydrocarbons for fuels, chemicals, and plastics. In its raw form, crude oil is a viscous, dark, tar-like substance, and its useful fractions must be separated by fractional distillation.

How Chain Length Affects Boiling Point00:00:56

Crude oil is a mixture of hydrocarbons with varying chain lengths. Shorter molecules have weaker intermolecular forces, requiring less energy to vaporize, thus having lower boiling points. Longer molecules have stronger intermolecular forces, needing more energy and higher temperatures to evaporate, resulting in higher boiling points.

The Fractional Distillation Process00:01:41

Crude oil is heated to a high temperature outside the fractionating column. The hot, mostly vaporized crude oil is then pumped into the column, which has a heat gradient—hot at the bottom and cooler at the top. Long-chain molecules with high boiling points condense at the bottom, while smaller molecules with lower boiling points rise higher before condensing due to the cooler temperatures. Bubble caps slow the rising vapor, allowing it to condense into liquid fractions.

Collecting Fractions and Their Uses00:02:52

Hydrocarbons with similar boiling points are collected in the same tray, forming 'fractions.' Examples of these fractions include petrol for cars, naphtha for chemical manufacturing, kerosene for aircraft fuel, diesel oil for vehicles, and pitch for laying roads.

Summary of Key Principles00:03:30

Fractional distillation separates crude oil into useful fractions based on their boiling points. Small-chain molecules with lower boiling points are collected at the top of the column, while larger-chain molecules with higher boiling points are collected further down.