Fractional Distillation | Organic Chemistry | Chemistry | FuseSchool

Summary

This video explains how fractional distillation is used to separate crude oil into useful fractions. Crude oil, a valuable mixture of hydrocarbons with varying chain lengths, is heated and turned into vapor. In the fractionating column, the temperature gradient causes longer-chain hydrocarbons with higher boiling points to condense lower in the column, while shorter-chain molecules condense higher up. Each fraction contains hydrocarbons with similar boiling points and has various applications, such as fuel for vehicles and aircraft, or materials like bitumen for road construction.

Takeaways

• 🛢️ Crude oil is unprocessed oil extracted directly from the ground or sea, consisting of a mixture of hydrocarbons with varying chain lengths.
• 🔬 Crude oil is valuable as it provides a wide range of organic compounds used for fuels, chemicals, and plastics.
• 🌡️ Fractional distillation is the process used to separate crude oil into useful fractions based on their boiling points.
• 🔗 The chain length of hydrocarbons in crude oil correlates with their boiling points; shorter chains have lower boiling points, while longer chains have higher boiling points.
• 🔥 The process begins by heating crude oil to a high temperature, turning it into vapor before it enters the fractionating column.
• 📉 The fractionating column has a heat gradient, with the highest temperature at the bottom and cooler temperatures towards the top.
• 💧 Longer molecules with high boiling points start to condense back into liquid at the bottom of the column.
• 🌀 Molecules rise through the column, slowed by bubble caps, and condense at different levels based on their boiling points.
• 🏔️ Small molecules with low boiling points condense higher in the column where it's cooler.
• 📦 Fractions collected at different levels of the column are known as fractions and have specific uses, such as petrol, naphtha, kerosene, diesel oil, and bitumen.
• 🔍 The separation of crude oil into fractions by fractional distillation is crucial for obtaining hydrocarbons with similar boiling points for various applications.

Q & A

What is crude oil, and why is it important?

Crude oil is unprocessed oil taken directly from the ground, either on land or under the sea. It is an exceptionally valuable resource because it provides a wide range of organic compounds used as fuels and in the manufacture of chemicals and plastics.

Why does crude oil need to be separated into fractions?

Crude oil in its raw form can be viscous and tar-like, making it less useful. To make it more useful, the different fractions of hydrocarbons within crude oil must be separated by fractional distillation.

What are hydrocarbons, and how do they differ in crude oil?

Hydrocarbons are molecules made up of carbon and hydrogen atoms. In crude oil, they vary in chain length, meaning they have different numbers of carbon atoms. Some hydrocarbons have short chains, while others have long chains.

How does chain length affect the boiling point of hydrocarbons?

The boiling point of hydrocarbons is influenced by their chain length. Shorter chain hydrocarbons have weaker intermolecular forces, requiring less energy to break apart and turn into a gas, resulting in lower boiling points. Longer chain hydrocarbons have stronger intermolecular forces, requiring more energy and therefore have higher boiling points.

What is the role of the fractionating column in fractional distillation?

The fractionating column is where the separation of crude oil into different fractions occurs. It has a heat gradient, being very hot at the bottom and cooler at the top, allowing hydrocarbons to condense at different levels based on their boiling points.

What happens to the hydrocarbons as they move up the fractionating column?

As hydrocarbons move up the fractionating column, they pass through bubble caps in each tray. As they rise, the temperature decreases, causing hydrocarbons with higher boiling points to condense lower in the column and those with lower boiling points to condense higher up.

Why are the hydrocarbons collected at different levels in the fractionating column called 'fractions'?

The hydrocarbons collected at different levels are called 'fractions' because they consist of mixtures of hydrocarbons with similar boiling points. Each fraction is a group of hydrocarbons that condense at the same temperature level in the column.

Can you give examples of some useful fractions obtained from crude oil?

Yes, some examples of useful fractions include petrol (used as fuel for cars), naptha (used in chemical manufacture and as fuel), kerosene (used as aircraft fuel), diesel oil (used as fuel for cars, vans, and lorries), and bitumen (used to lay roads and on roofs).

Why do small chain molecules condense at the top of the fractionating column?

Small chain molecules have lower boiling points, so they rise higher in the fractionating column where the temperature is cooler and condense at the top.

What should you understand by the end of this video about fractional distillation?

By the end of the video, you should understand that crude oil is a mixture of important hydrocarbons, and fractional distillation is the method used to separate it into useful fractions with similar boiling points. Small chain molecules condense at the top of the column due to their lower boiling points, while large chain molecules condense further down due to their higher boiling points.