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.

Outlines

00:00

🛢️ Crude Oil Fractional Distillation

This paragraph introduces fractional distillation as a method to separate crude oil into useful fractions. Crude oil, extracted directly from the ground or sea, is a valuable resource that contains organic compounds used as fuels and in chemical and plastic manufacturing. It is described as a mixture of hydrocarbons with varying chain lengths, which affects their boiling points. Shorter hydrocarbon chains have weaker intermolecular forces and lower boiling points, while longer chains have stronger forces and higher boiling points. The process of fractional distillation is explained, where crude oil is heated and introduced into a fractionating column with a heat gradient. The column separates the hydrocarbons based on their boiling points, with shorter chain molecules condensing higher up and longer chains lower down. The fractions collected have various applications, such as petrol for cars, naphtha for chemical manufacturing, kerosene for aircraft fuel, diesel oil for vehicles, and bitumen for road and roof construction.

Keywords

💡Crude Oil

Crude oil refers to unprocessed oil that is extracted from the ground. It is a natural resource consisting of a mixture of hydrocarbons and is valuable for producing various fuels and chemicals. In its raw form, crude oil is often viscous and dark, and needs to be separated through fractional distillation to be useful.

💡Fractional Distillation

Fractional distillation is a method used to separate crude oil into different fractions, based on their boiling points. The process involves heating crude oil and allowing hydrocarbons to condense at different levels of a fractionating column, where fractions with similar boiling points are collected together. This method is essential for refining crude oil into useful products like fuels.

💡Hydrocarbons

Hydrocarbons are organic compounds consisting of hydrogen and carbon atoms. In the context of crude oil, hydrocarbons vary in chain length, which affects their boiling points and uses. Some hydrocarbons are used as fuels, while others are key in manufacturing chemicals and plastics. The video emphasizes the importance of separating hydrocarbons by fractional distillation.

💡Boiling Point

The boiling point refers to the temperature at which a substance changes from liquid to gas. In fractional distillation, hydrocarbons with lower boiling points vaporize and rise higher in the fractionating column, while those with higher boiling points condense earlier at the bottom. This concept is central to how fractional distillation separates crude oil.

💡Intermolecular Forces

Intermolecular forces are the forces that act between molecules, influencing their physical properties like boiling points. In the video, it’s explained that hydrocarbons with longer chains have stronger intermolecular forces, requiring more energy (and a higher temperature) to turn into gas, affecting how they are separated in fractional distillation.

💡Fractionating Column

The fractionating column is a tall structure used in fractional distillation. It has a temperature gradient, being hottest at the bottom and cooler at the top. Hydrocarbon vapors rise through the column, condensing on trays at different levels depending on their boiling points. The column allows for the effective separation of hydrocarbons into fractions.

💡Fractions

Fractions are the separated groups of hydrocarbons that have similar boiling points, collected at different levels in the fractionating column. Each fraction has specific uses, such as petrol for cars, kerosene for aircraft, and diesel for trucks. These fractions are critical products derived from crude oil through fractional distillation.

💡Chain Length

Chain length refers to the number of carbon atoms in a hydrocarbon molecule. The video explains that hydrocarbons with shorter chain lengths have lower boiling points and weaker intermolecular forces, while longer chains have higher boiling points. This property determines where hydrocarbons condense in the fractionating column during fractional distillation.

💡Petrol

Petrol is one of the useful fractions obtained through fractional distillation of crude oil. It is a fuel used primarily in cars. The video lists petrol as an example of a hydrocarbon fraction with a low boiling point, condensing near the top of the fractionating column where the temperature is cooler.

💡Bitumen

Bitumen is a heavy fraction of hydrocarbons collected at the bottom of the fractionating column. It has a high boiling point and consists of long-chain hydrocarbons. Bitumen is commonly used in construction, particularly for paving roads and roofing, due to its thick, tar-like consistency.

Highlights

Crude oil is unprocessed oil taken directly from the ground or sea.

Crude oil is a valuable resource providing organic compounds for fuels and chemicals.

Crude oil in its raw form is viscous and dark colored.

Fractional distillation is necessary to separate crude oil into useful fractions.

Crude oil is a mixture of hydrocarbons with varying chain lengths.

Intermolecular forces vary with chain length, affecting boiling points.

Shorter molecules have lower boiling points due to weaker intermolecular forces.

Longer molecules require higher temperatures to evaporate, indicating higher boiling points.

Fractional distillation separates hydrocarbons based on boiling points.

Heating crude oil initiates the fractional distillation process.

The fractionating column has a heat gradient, hottest at the bottom.

Long chain molecules condense at the bottom of the column.

Bubble caps in the column slow down vapor and aid in condensation.

Small molecules condense higher in the column due to lower boiling points.

Fractions are collected in trays based on similar boiling points.

Each fraction has specific uses, such as petrol for cars or kerosene for aircraft.

Fractional distillation is essential for converting crude oil into valuable products.

Transcripts

In this video you will learn how fractional distillation separates crude oil into useful

fractions.

Crude oil is the term used to describe unprocessed oil.

That is oil that has been taken directly out of the ground either on land or under the

sea.

It is an exceptionally valuable resource.

It provides us with a great number of organic compounds some of which are used as fuels

and others are used in the manufacture of many different chemicals and even plastics.

However, in the raw form as crude oil, it can be of a viscous dark coloured tar like

consistency and the different fractions of hydrocarbons must be separated by fractional

distillation for them to be useful.

Before we understand how fractional distillation works, we should be clear that crude oil is

a mixture of hydrocarbons with different chain lengths.

That means that there are different numbers of carbon atoms making up the molecule -- some

molecules are short with only a few carbons in the chain and some are very long.

Intermolecular forces act between molecules and the longer the molecule, the greater the

intermolecular force.

As you can see here, the small molecules have weaker intermolecular forces and so will require

less energy to break them apart and turn them into a gas -- they have a low boiling point.

The longer molecules have greater intermolecular forces and more energy, therefore higher temperature

will be needed to evaporate these molecules -- they have a higher boiling point.

Now we understand how chain length is related to the boiling point of a molecule, let us

look at how this method works.

As you can see, crude oil is heated up to a high temperature outside of the fractionating

column.

The hot crude oil, now mostly in vapour form is pumped into the column.

The column has a heat gradient and is very hot at the bottom going cooler as we move

up to the top.

Even at the very bottom of the column where the temperature is still high, some long chain

molecules with high boiling points begin to condense back into a liquid and are collected

at the bottom of the column.

The rest of the molecules start to rise up the column, making their way through bubble

caps in each tray.

The bubble caps slow down the rate of the rising vapour and eventually the vapours gets

too cool, condense and are collected trays.

Small molecules have low boiling points and so condense much higher in the column where

the temperature is cooler still.

As you can see, hydrocarbons with similar boiling points are collected in the same tray

and this is why they are known as fractions -- they are mixtures of hydrocarbons with

similar boiling points.

Each fraction has important uses.

Some examples of fractions are ,Petrol useful as a fuel for cars, Naptha used in the manufacture

of chemicals and as a fuel, Kerosine as aircraft fuel, Diesel oil used as a fuel for cars,vans

and lorrys and Buitmen, a mixture of large chain hydrocarbons used to lay roads and on

roofs.

Now, at the end of this video you should understand that crude oil is a mixture of important hydrocarbons

and that fractional distillation is the method used to separate crude oil into useful fractions

with similar boiling points.

You should understand that small chain molecules are collected at the top of the column since

they have lower boiling points and large chain molecules further down the column as these

have higher boiling points.