# Keywords: Fractionating column, fractions

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Keywords: Fractionating column, fractions
Fractional distillation Prior Learning: Know what a hydrocarbon & alkane is. Keywords: Fractionating column, fractions

Learning Objectives: Identify and explain
• That crude oil is separated using fractional distillation. • The properties of each fraction and how they relate to chain length. • Which fractions make useful fuels and why. I will be successful in this lesson if I can: (Level C) • State that crude oil is separated into fractions by fractional distillation. • List how the properties change from small chain fractions to long chain fractions. • State which fractions are useful fuels. (Level A) • Explain the key steps involved in fractional distillation. • Relate the trend in properties to molecular size.

What fuels have you used already today?
Cooking Gas Charcoal Transport Petrol Diesel Gas Heating Oil Gas Lighting Gas Oil Even electricity is likely to have been produced by fossil fuels

Consider this diagram & these keywords
MIXTURE HEAT BOIL SEPARATE SEPARATE MIXTURE BOIL HEAT

Fractional Distillation
What is it??? Where is crude oil formed and how is it extracted? What is crude oil? What are the simple state changes used in this distillation? What property of the crude oil fractions cause them to separate in the fractionating column?

Fractional Distillation
Produced deep in the earth from the long term heat and pressure of animal and plant remains. It is either pumped to the surface or rises due to its own pressure. Crude oil is a mixture of many hydrocarbons. Condensation (gas to liquid) and evaporation (liquid to gas). Boiling point will separate the fractions. The lighter fractions (less smaller carbon chains – smaller molecules, lighter in colour) have a lower boiling point and so will move up the fractionating column. Inside the column there are many trays with holes to let gases through. Vapours move up the column & condense on the trays when they reach their bp. Fractions with low bp burn more easily which makes them useful as fuels. What would you expect to collect from the top of the column?

Fractional Distillation Demonstration
Soak mineral wool in crude oil and place in a boiling tube. 2. Fix the thermometer bung & side arm. 3. Gently heat the boiling tube. when the temperature stabilises at about 80oC then 1 type of fraction is separated. 4. Change the collecting tube as the temperature rises again. 5. Repeat step 4 four times collecting five fractions & leaving the residue in the boiling tube. 6. Tip each fraction onto mineral wool & ignite.

Fractional Distillation
Once fractions are collected, they need more refining before they can be used.

What further patterns have you found with the fractions?

Teacher notes This activity could be used as a plenary exercise to check students’ ability to identify uses of fractions. Class voting or the use of mini whiteboards could make this a whole-class exercise.

Over 85% of crude oil is used as a fuel for heating and transport
Over 85% of crude oil is used as a fuel for heating and transport. Only 8% is used to make plastics and other chemicals. A large amount of oil is used as fuel because the hydrocarbons in the fractions burn easily and produce a large amount of useful energy. Photo credit: BP plc A fuel is a substance that reacts with oxygen to produce useful energy.

Liquid petroleum gas (LPG) contains propane and butane
Liquid petroleum gas (LPG) contains propane and butane. They are stored under pressure in metal cylinders. LPG is used for heating and cooking, especially where piped gas cannot be used, such as camp sites and boats. Photo credit (left): Dain Hubley Photo credit (right): BP plc

Gasoline is one of the most important fractions because it is used as a fuel for cars.
The gasoline fraction must be refined before it can be used in cars as petrol. Impurities are removed, and chemicals are added to ensure the engine runs smoothly. Photo credit: Vitezslav Valka In the past, these chemicals were lead compounds but because of lead’s harmful effect on health and the environment, they have been replaced by safer compounds.

a raw material (feedstock) in the production of chemicals and plastics
Naphtha is a very important fraction that has many uses. For example, it is: a raw material (feedstock) in the production of chemicals and plastics Teacher notes This toy petrol tanker is made from plastic. used as a cleaning fluid and industrial solvent (a substance that can dissolve another substance) added to petrol and other fuels.

Kerosene, also called paraffin, is mainly used as aviation fuel for jet aircraft. It is also used in central heating systems, lamps and stoves. Diesel is mainly used as a fuel for lorries, buses and cars, and in some boats. Photo credit (top): Aaron Murphy Photo credit (bottom): Margus Kyttä

Lubricating oil, as its name suggests, is used as a lubricant in products with moving parts, such as engines. Fuel oil is a heavy fraction used as a fuel for large industrial boilers, oil-fired power stations and ships. Photo credit (top): David Dallaqua Photo credit (bottom): Lewis Johnston

Bitumen is used in road construction and waterproof roof material.
Residue contains paraffin waxes and bitumen, the heaviest product to come from an oil refinery. Paraffin waxes (not the same as paraffin/kerosene) are used in candles and waterproofing. Photo credit (top): Russell Curtis Photo credit (bottom): BP plc Bitumen is used in road construction and waterproof roof material.

Teacher notes This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of fractions from oil. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.

Learning Objectives: Identify and explain
• That crude oil is separated using fractional distillation. • The properties of each fraction and how they relate to chain length. • Which fractions make useful fuels and why. I will be successful in this lesson if I can: (Level C) • State that crude oil is separated into fractions by fractional distillation. • List how the properties change from small chain fractions to long chain fractions. • State which fractions are useful fuels. (Level A) • Explain the key steps involved in fractional distillation. • Relate the trend in properties to molecular size.