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Boardworks GCSE Science: Chemistry Making Oil Useful

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Presentation on theme: "Boardworks GCSE Science: Chemistry Making Oil Useful"— Presentation transcript:

1 Boardworks GCSE Science: Chemistry Making Oil Useful

2 Boardworks GCSE Science: Chemistry Making Oil Useful

3 Boardworks GCSE Science: Chemistry Making Oil Useful
What is crude oil? Boardworks GCSE Science: Chemistry Making Oil Useful Crude oil is a fossil fuel and one of the most important substances in the world. It is a mixture of hundreds of different compounds. Crude oil is used to make fuels for transport, heating and generating electricity. It is also used to make plastics and hundreds of different types of chemicals. Teacher notes Data from OPEC ( Photo credit: BP plc Every day, the world uses over 70 million barrels of oil. If you filled bath tubs with this amount of oil and put them end-to-end, they would stretch round the Earth 7.5 times!

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How was crude oil made? Boardworks GCSE Science: Chemistry Making Oil Useful Crude oil is thought to have been made from the remains of marine plants and animals that died millions of years ago. These remains sank to the bottom of the sea, where they were buried in layers of sand and mud, preventing them from rotting. These layers gradually became sedimentary rock. Over millions of years the layers of rock built up, increasing the heat and pressure. This caused the remains to be broken down into the molecules that form crude oil and natural gas.

5 Hydrocarbons in crude oil
Boardworks GCSE Science: Chemistry Making Oil Useful Many compounds in crude oil only contain the elements carbon and hydrogen. They are called hydrocarbons. Most hydrocarbons in crude oil are compounds called alkanes. Alkanes contain a single chain of carbon atoms with hydrogen atoms bonded along the side.

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What are alkanes? Boardworks GCSE Science: Chemistry Making Oil Useful Alkanes are a family of hydrocarbon compounds with the general formula CnH2n+2. The simplest alkane is methane. It has the formula CH4. The second simplest alkane is ethane. It has the formula C2H6. Teacher notes The alkanes are a homologues series and it should be pointed out to students that the general formula allows the molecular formula of any alkane to be determined. The naming of alkanes could also be introduced, making it clear that all alkanes end in ‘-ane’. The start of the name denoted the number of carbon atoms in each molecule. The third simplest alkane is propane. It has the formula C3H8.

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8 How can crude oil be made useful?
Boardworks GCSE Science: Chemistry Making Oil Useful Crude oil itself has no uses – it must first be processed or refined. This is done in an oil refinery. The first step is to separate compounds in the oil into groups called fractions. Each fraction contains a mix of compounds with a similar number of carbon atoms. Photo credit: BP plc The Singapore Refinery, formerly owned by BP.

9 Molecule size and boiling point
Boardworks GCSE Science: Chemistry Making Oil Useful Molecules in crude oil can contain anything from just 1 carbon atom to well over 50. The more carbon atoms in a hydrocarbon molecule, the larger the molecule. How does this affect its boiling point? Generally, the larger a hydrocarbon, the higher its boiling point. This is because the intermolecular forces between large molecules are stronger than the intermolecular forces between small molecules. Teacher notes The boiling point of hydrocarbons increases with the size of the molecule due to increasing surface area. A larger surface area means a larger van der Waals intermolecular force between adjacent molecules. More energy is needed to break the forces between large molecules, and so the boiling point is higher.

10 What is fractional distillation?
Boardworks GCSE Science: Chemistry Making Oil Useful Fractional distillation is a process used to separate a mixture of liquids that have different boiling points. When the mixture is heated, liquids with a low boiling point evaporate and turn to vapour. Liquids with a higher boiling point remain as liquid. The vapour can then be separated from the liquid. Fractional distillation is used to separate crude oil into fractions with different boiling points. It can be done industrially and in the laboratory.

11 Fractional distillation of crude oil
Boardworks GCSE Science: Chemistry Making Oil Useful Crude oil is separated into fractions by fractional distillation. 1. Oil is heated to about 450 °C and pumped into the bottom of a tall tower called a fractionating column, where it vaporizes. 2. The column is very hot at the bottom but much cooler at the top. As the vaporized oil rises, it cools and condenses. 3. Heavy fractions (containing large molecules) have a high boiling point and condense near the bottom of the column. 4. Lighter fractions (containing small molecules) have a lower boiling point and condense further up the column.

12 How does fractional distillation work?
Boardworks GCSE Science: Chemistry Making Oil Useful Teacher notes This six-stage interactive animation shows how fractional distillation is used on an industrial scale to separate crude oil into different fractions. At the end of the animation, you can view a summary of each fraction by clicking on its name. While showing the animation, the one-way nature of the bubble caps could be highlighted. Suitable prompts could include: What is special about the molecules in a fraction? Which fraction will be the hardest to vaporise? Why is the vapour slowed down by the bubble caps as it rises up the column? What makes the fractions condense at different heights in the column? Will all the molecules that enter the column condense? Are the molecules in a fraction identical?

13 Fractional distillation in the lab
Boardworks GCSE Science: Chemistry Making Oil Useful Fractional distillation of crude oil can be done in the laboratory by heating crude oil and collecting the vapour produced at different temperatures. fractions collected previously (at lower temperatures) mineral wool soaked in crude oil cooling water

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Order of fractions Boardworks GCSE Science: Chemistry Making Oil Useful Teacher notes This ordering activity could be used as a plenary or revision exercise on the order of fractions in a fractionating column. Mini-whiteboards could be used to make this a whole-class exercise.

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Supply and demand Boardworks GCSE Science: Chemistry Making Oil Useful The amount of each type of fraction obtained by fractional distillation does not usually match the amount of each fraction that is needed. Crude oil often contains more heavier fractions than lighter fractions. Lighter fractions are more useful and therefore more desirable. The large hydrocarbon molecules in the heavier fractions can be broken down into smaller, more useful, molecules to meet demand for raw materials for fuels and plastics.

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Catalytic cracking Boardworks GCSE Science: Chemistry Making Oil Useful Large hydrocarbon molecules can be broken down into smaller molecules using a catalyst. This is called catalytic cracking, and is an example of a thermal decomposition reaction. The hydrocarbon molecules are heated until they turn into vapour, and then mixed with a catalyst. The molecules break apart, forming smaller alkanes and alkenes. Teacher notes It may be worth pointing out to students that the molecules crack – rather than burn – when heated, because oxygen is kept out of the reaction vessel. Alkenes are reactive molecules that are used to make plastics and other chemicals.

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What are alkenes? Boardworks GCSE Science: Chemistry Making Oil Useful Alkenes are a family of hydrocarbon compounds with the general formula CnH2n. Alkenes are very similar to alkanes, but they have one important difference: they contain at least one double covalent bond between carbon atoms. The simplest alkene is ethene. It has the formula C2H4. Teacher notes The alkenes are a homologues series and it should be pointed out to students that the general formula allows the molecular formula of any alkene to be determined. The naming of alkenes could also be introduced, making it clear that all alkenes end in ‘-ene’. The start of the name denoted the number of carbon atoms in each molecule. The second simplest alkene is propene. It has the formula C3H6.

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Cracking decane Boardworks GCSE Science: Chemistry Making Oil Useful Decane from the naphtha fraction can be cracked to form pentane (for use in petrol), propene and ethene. decane (C10H22) pentane (C5H12) propene (C3H6) ethene (C2H4) +

20 Saturated vs. unsaturated
Boardworks GCSE Science: Chemistry Making Oil Useful Alkanes are examples of saturated compounds. A saturated compound only contains single covalent bonds between carbon atoms. Alkenes are examples of unsaturated compounds. An unsaturated compound contains at least one double covalent bond between carbon atoms. A test to distinguish between saturated and unsaturated compounds is to add red bromine water. In the presence of unsaturated compounds, the red colour disappears.

21 How does catalytic cracking work?
Boardworks GCSE Science: Chemistry Making Oil Useful Teacher notes This six-stage interactive animation shows how catalytic cracking is used on an industrial scale to break down large fractions into smaller, more useful fractions. Suitable prompts could include: Which fractions of oil would it be best to crack? What makes the hydrocarbon molecules break up? Would you expect all the products to be the same? How could you separate the mixture of alkanes and alkenes produced? Would you expect the catalyst to be used up during the reaction?

22 Catalytic cracking in the lab
Boardworks GCSE Science: Chemistry Making Oil Useful Catalytic cracking can be done in the laboratory by heating mineral wool soaked in oil with a catalyst, producing a gas. aluminium oxide catalyst gaseous product mineral wool soaked in oil What might this gas be?

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True or false? Boardworks GCSE Science: Chemistry Making Oil Useful Teacher notes This true-or-false activity could be used as a plenary or revision exercise on refining crude oil, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

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Glossary (1/2) Boardworks GCSE Science: Chemistry Making Oil Useful alkanes – A family of hydrocarbon molecules with the general formula CnH2n+2. alkenes – A family of hydrocarbon molecules with the general formula CnH2n. catalytic cracking – A reaction where a large molecule is broken down into smaller molecules in the presence of a catalyst. crude oil – A naturally-occurring mixture of different-sized hydrocarbon molecules. fraction – A mixture of hydrocarbon molecules of a similar size.

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Glossary (2/2) Boardworks GCSE Science: Chemistry Making Oil Useful fractional distillation – The process used to separate crude oil into different fractions. hydrocarbon – A molecule containing only hydrogen and carbon. saturated – A compound that only contains single covalent bonds between carbon atoms. unsaturated – A compound that has at least one double covalent bond between carbon atoms.

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Anagrams Boardworks GCSE Science: Chemistry Making Oil Useful

28 The stages of fractional distillation
Boardworks GCSE Science: Chemistry Making Oil Useful Teacher notes This ordering activity could be used as a plenary or revision exercise on fractional distillation. Mini-whiteboards could be used to make this a whole-class exercise.


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