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© Boardworks Ltd 2003 Cracking
© Boardworks Ltd 2003 Cracking Crude oil contains many large molecules. If these are to be used as fuels or feedstock for the chemical industry then they have to be cracked into smaller molecules. When hydrocarbons burn they are reacting with oxygen in the air. In general, the smaller the molecule the better it will mix and then react with the air. Big molecules Small molecules Medium molecules
© Boardworks Ltd 2003 Involves the breaking of C-C bonds in alkanes Converts heavy fractions into higher value products THERMALproceeds via a free radical mechanism CATALYTICproceeds via a carbocation (carbonium ion) mechanism CRACKING Cracking
© Boardworks Ltd 2003 High Pressure... 7000 kPa High Temperature... 400°C to 900°C Free Radical Mechanism Homolytic fission Produces mostly alkenes... e.g. ethene for making polymers and ethanol Produces Hydrogen... used in the Haber Process and in margarine manufacture Bonds can be broken anywhere in the molecule by C-C bond fission or C-H bond fission Thermal Cracking
© Boardworks Ltd 2003 Slight pressure High Temperature... 450°C Zeolite catalyst Carbocation Mechanism Heterolytic fission Produces branched and cyclic alkanes, aromatic hydrocarbons used for motor fuels ZEOLITES are crystalline aluminosilicates; clay like substances Catalytic Cracking
© Boardworks Ltd 2003 Catalytic Cracking Large hydrocarbons are broken into smaller molecules using heat and a catalyst. This process is known as catalytic cracking. The small molecules produced are then separated by distillation. Catalytic cracker Heat to vaporise Distillation tower pressure Big Molecules Smaller molecules Molecules break up
© Boardworks Ltd 2003 Catalytic Cracking In the catalytic cracker long chain molecules are ‘cracked’. An example of such a reaction is: C 8 H 18 C 6 H 14 + C 2 H 4 + ethene Octane hexane Ethene is used to make plastics Heat pressure catalyst Used as a fuel
© Boardworks Ltd 2003 Draw out displayed formulae of a pair of products formed by cracking decane Heat pressure catalyst HH CC H HH HH C C HH HH CC HH HH CC HH HH CC HH H decane + ethene HH CC H HH HH C C HH HH CC HH H C H H C H H octane Activity
© Boardworks Ltd 2003 Poly(e)thene One important reaction of alkenes involves the joining together of alkene molecules. HH CC H HH HH C C HH HH CC HH HH CC HH HH CC HH And lots more.. addition polymerisation This is called addition polymerisation and is written as: Pressure high temperature catalyst n n ethene poly(e)thene 1 2 3 4 5 thousands
© Boardworks Ltd 2003 Polypropene polymerisedEthene is only one alkene. Other unsaturated molecules such as propene, vinyl chloride and styrene can also be polymerised to produce a range of plastics. E.g. propene Poly(propene) n n propene
© Boardworks Ltd 2003 PTFE Tetrafluoroethane is another alkene that is made into an important plastic used to coat non-stick pans: polytetrafluoroethane or PTFE. n tetrafluoroethene Poly(tetrafluoroethane) or PTFE n
© Boardworks Ltd 2003 pvc CC HH H Cl n n Vinyl chloride CC Cl H HH Fill in the products that will be obtained from vinyl chloride Activity
© Boardworks Ltd 2003 Some uses of plastics Poly(e)thene Shopping bags Bottles Buckets Washing up bowls Polypropene Milk crates Rope Carpet fibres Polystyrene packing insulation Ball pens
© Boardworks Ltd 2003 12 3 456 7 8 9 AcrossDown 3) separate substances with different boiling points 1) Contain a double bond 7) saturated hydrocarbon 2) a series of molecules differing by a CH2 8) joining of many small molecules 4) breaking up a large molecules 9) full up: unable to add more atoms 5) the different substances collected from distillation 6) used to test for unsaturated molecules.
© Boardworks Ltd 2003 AcrossDown 3) separate substances with different boiling points DISTILLATION 1)Contain a double bond ALKENE 7) saturated hydrocarbon ALKANE 2) a series of molecules differing by a CH2 HOMOLOGOUS 8) joining of many small molecules POLYMERISE 4) breaking up a large molecules CRACKING 9) full up: unable to add more atoms SATURATED 5) the different substances collected from distillation FRACTIONS 6) used to test for unsaturated molecules. BROMINE Answers
© Boardworks Ltd 2003 Which of these is an alkane? A.C 6 H 14 B.C 4 H 8 C.C 12 H 24 D.C 102 H 204
© Boardworks Ltd 2003 Which of these is a true statement about alkenes? A.They turn bromine water from colourless to red B.They contain a double bond C.The smallest alkene has 1 carbon atom D.They have names that end in “ane.”
© Boardworks Ltd 2003 Which of these is a true statement about cracking? A. it is the separation of molecules into fractions of different sizes. B. it is carried out at low temperatures C. it uses a catalyst. D. It produces polymers
© Boardworks Ltd 2003 Which of these is a true statement about polymerisation? A.it is the joining together of many small molecules. B. it is the thermal decomposition of plastics C.it is carried out using saturated molecules D.it is a multiplication reaction
© Boardworks Ltd 2003 Which of these is an addition polymer? A.styrene B.ethene C.p.v.c. D.propane
© Boardworks Ltd 2003 How might you test to see if polystyrene still contained some unsaturated monomer (styrene)? A.Crush it up and burn it. B.Crush it up and add it to bromine water C.Crush it up and dissolve it in petrol D.Crush it up and add hydrochloric acid
© Boardworks Ltd 2003 Industrial manufacture and uses of Alkenes.
1.Alkanes are hydrocarbons in which all carbon atoms are bonded by single covalent bonds 2.Alkanes are said to be saturated because all the bonds are.
© Boardworks Ltd 2003 Organic Chemistry Alkanes and Alkenes.
Polymerisation Copy essential keyword definitions into books; Monomer = Small molecules which may join together. Polymer = A long chain of repeating monomer.
Alkanes and Alkenes. Alkenes Alkanes Summary activities Combustion of alkanes Contents Cracking and polymerization.
© Boardworks Ltd of 45 KS4 Chemistry Alkanes and Alkenes.
HYDROCARBONS – FUELS. In the past, most important organic chemicals were derived from coal. Nowadays, natural gas and crude oil provide an alternative.
Slime Practical Place 40 cm 3 of PVA solution into the plastic cup. Measure out 10 cm 3 of borax solution and add this to the PVA solution. Stir until.
© Boardworks Ltd 2003 Section 3 Organic Chemistry Alkanes and Alkenes.
Cracking!03 September 2015 Learning objective: To know what cracking is and why it’s so useful! Starter Name fractions from the fractional distillation.
Cracking Hydrocarbons L.O: To understand what cracking is and why it is useful A food packaging company is low on ethene to make polythene (cling film),
Alkanes 2/17/2016Dr Seemal Jelani Chem Least reactive Acids have no effects Strong oxidizing and reducing agents have little effect on alkanes.
© Boardworks Ltd of 37. © Boardworks Ltd of 37 Supply and demand The amount of each type of fraction obtained by fractional distillation does.
MAKING POLYMERS L.O: To understand how polymers can be made from alkenes.
Cracking involves breaking down larger crude oil fractions into smaller more useful hydrocarbons. This reaction involves heating the crude oil fraction.
2 3 18/09/2015 Monomers and Polymers Ethene Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene.
© Boardworks Ltd 2001 KS4: Useful Products from Organic Sources ORGANIC CHEMISTRY.
Alkenes a group of hydrocarbons with the general formula, C n H 2n where n is the number of carbon atoms in one molecule contain the C=C functional.
Fractional distillation of crude oil Industrial cracking and catalytic cracking By Craig Wilson.
mmcl * Information available.
Substances from Crude Oil C1.5. What do I need to know? Recall how hydrocarbons can be cracked to make smaller more useful molecules. Describe some of.
GCSE Science C1b Oils, Earth and Atmosphere. Completed by 20 th November 8 weeks till exam But… Additional Applied Science as well 5 lessons a week =
© Boardworks Ltd of 37. © Boardworks Ltd of 37.
Alkanes and Alkenes Topic 10.2 and Alkanes have low reactivity bond enthalpies are relatively strong 348 kJ mol -1 to break a C-C bond 412 kJ mol.
Calderglen High School
SYNTHESIS PART ONE HYDROCARBONS. What is organic chemistry? In chemistry chemicals which contain carbon are classed as organic. Carbon is a non metal.
10.3 Alkenes. References Assessment Objectives Describe, using equations the reactions of alkenes with hydrogen and halogens Describe,
Making polymers from alkenes You should be able to: Know how polymers are formed Understand how to name polymers List some uses of polymers.
1 of 28© Boardworks Ltd 2011 Smart Teach Chemistry Section 5 Fuels.
Polymers Chapter 21. Introduction O What is a polymer? O A very large molecule made up of identical smaller units (minimum 50), which repeat. O Monomer?
© Oxford University Press 2011 IC Images Images.
Atmosphere BY JACK HARFIELD. The gases in the atmosphere The common name air is given to the atmospheric gases used in breathing and photosynthesis. By.
IGCSE CHEMISTRY SECTION 5 LESSON 3. Content The iGCSE Chemistry course Section 1 Principles of Chemistry Section 2 Chemistry of the Elements Section 3.
Cracking Lesson Objective: To be able to explain cracking and its uses. - Recall what cracking means (C) -Explain why some hydrocarbons are more useful(B)
Title: Lesson 4 Alkenes Learning Objectives: – Describe the main addition reactions of the alkenes – Extract an alkene from a citrus fruit.
Hydrocarbons. Molecules which contain the elements HYDROGEN and CARBON ONLY Increasing molecular size Decreasing Flammability Increasing boiling point.
Starter 1.What does the word ‘synthetic’ mean? 2.What does the word ‘biodegradable’ mean? 3.Give 2 advantages of synthetic materials over natural materials.
Refining Crude Oil Picture courtesy of HowStuffWorks Copyright © HowStuffWorks, Inc. All rights reserved.
Alkanes, Alkenes and Polymers CHEMISTRY 2 GCSE Additional ScienceChapter 9.
Ethylene What is ethylene? What is cracking? Why do we do it?
Objectives: To revise fractional distillation. To explain why large hydrocarbons are cracked. Outcomes: All of you will be able to explain what is meant.
Alkenes and Ethanol. Recap from last lesson- To evaluate 2 ways in which ethanol fuel is made To extract oil from a fruit like avocados To describe.
Topics 3abc – Alkanes, alkenes and ethanol Topics 5bc – natural oil and gas and synthetic polymers.
Reactions of Alkenes Section Introduction Alkenes are unsaturated The double bond in ethene, for example, has one sigma bond and one pi bond (2.
ALKENES ( 2 nd ) Dr. Marwa Eid 1. Alkenes – unsaturated hydrocarbons (C n H 2n ) reactivity: the double bond is responsible for their reactivity 1.
Organic Chemistry Revision Grade 10. What is crude oil? It is a mixture of hydrocarbons.
Nat 4/5 Calderglen High School * Information available Calderglen.
Chapter 8 Compounds of Carbon. Why is Carbon important? T hey make up over 90% of all chemical compounds, is the backbone of all living things. Make.
Standard Grade Revision Units 5 and 6 (a) A chemical which burns giving out energy. (b) Coal and natural gas. (c) Formed from dead sea animals. Remains.
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