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Welcome to this Kent Triple Science Network Webinar

Welcome to this Kent Triple Science Network Webinar. If you are here early you might like to Download resources of interest shown on the top right Download this PowerPoint (the bottom file in the list). You could then open it to view notes and type in notes as the session is ongoing.

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Welcome to this Kent Triple Science Network Webinar

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  1. Welcome to this Kent Triple Science Network Webinar If you are here early you might like to Download resources of interest shown on the top right Download this PowerPoint (the bottom file in the list). You could then open it to view notes and type in notes as the session is ongoing.

  2. Carbon ChemistryMaking sense of millions of moleculesJohn Coad18th July 2013

  3. Carbon Chemistry – some difficulties New vocabulary • Lots of new language Naming compounds • Try to emphasise the logic of the naming system Drawing formulae and writing equations • Difficult to appreciate 3D shapes from representation on paper • Symbol equations can be daunting. Showing structures adds clarity but it is another skill for students to master.

  4. Useful products from crude oil • Hydrocarbons (alkanes) and hydrocarbon fuels • Cracking and alkenes • Addition reactions • Polymerisation • Properties, uses and environmental impact of polymers • Other useful products from crude oil - ethanol • Properties of alcohols and carboxylic acids • Esters • Soaps Carbon chemistry in pre-16 courses

  5. Starting point:Crude oil – it’s a mixture Total world oil reserves

  6. Laboratory Scale Fractional Distillation See RSC practical guide – ECARBON1

  7. Industrial Scale Fractional Distillation Animation 1 Animation 2 Image by Psarianos, Theresa knott, available at http://commons.wikimedia.org/wiki/File:Crude_Oil_Distillation-en.svg

  8. Modelling Fractional Distillation of Oil Small molecules  Small overlap between molecules  Small intermolecular force between molecules  Small amount of energy to separate molecules  Low boiling point (also low viscosity) How fractional distillation works Larger molecules  Larger overlap between molecules  Larger intermolecular force between molecules  Larger amount of energy to separate molecules  Higher boiling point (also higher viscosity)

  9. Increasing amount of oxygen required for complete combustion Large molecules harder to ignite and greater chance of incomplete combustion Complete combustion of alkanes CH4 + 2O2 CO2 + 2H2O C2H6 + 3½O2  2CO2 + 3H2O C3H8 + 5O2 3CO2 + 4H2O C4H10 + 6½O2  4CO2 + 5H2O C5H12 + 8O2  5CO2 + 6H2O C6H14 + 9½O2  6CO2 + 7H2O C7H16 + 11O2  7CO2 + 8H2O C8H18 + 12½O2  8CO2 + 9H2O C9H20 + 14O2  9CO2 + 10H2O

  10. Incomplete combustion of alkanes C8H18 + 4½O2  8C + 9H2O small amount of oxidation C8H18 + 5½O2  6C + 2CO + 9H2O …a bit more C8H18 + 5½O2  7C + CO2 + 9H2O …or could be this C8H18 + 8½O2  8CO + 9H2O …and yet more oxidation

  11. Structures of alkanes These structures are different – they are isomers From C4H10 (butane) onwards more than one structure is possible. These structures are the same How many isomers of C5H12?

  12. Naming of alkanes

  13. Cracking Breaking big molecules to produce smaller ones See RSC practical guide – ECARBON2 Animation

  14. Testing alkenes for unsaturation Ethene (colourless) + Bromine (orange/brown) 1,2-dibromoethane (Colourless liquid) C2H4 + Br2 C2H4Br2

  15. Using alkenes for addition polymerisation H H H H Heat, pressure, catalyst • “Opening-up” the double bond allows alkene molecules to join together into chains. C=C C C n H H H H n • Examples of addition polymers: • Polythene, polypropene, polystyrene, PVC, PTFE (“Teflon”), • polymethyl methacrylate (“Perspex”) If you illustrate other examples, work from the structure C=C Where X might be CH3, Cl, C6H5 X

  16. Condensation polymerisation Reaction between monomers which each have TWO reactive functional groups. Monomers can be the same or different. Reaction results in the formation of a small molecule by-product. Examples of condensation polymers: Nylon, Kevlar, polyester, polyurethane.

  17. Polymers and the Environment Issues Non-renewable sources Disposal Resolving issues Public awareness Use of renewable sources – plants Making polymers degradable Improving recycling Precycling?

  18. More on Polymers From SEP (Science Enhancement Programme) Download from www.nationalstemcentre.org.uk Booklets (Innovations in Practical Work) and worksheets Recycling and Sustainability Fantastic Plastic Fibres and Fabrics

  19. Like alkanes but with a hydroxyl group in place of a hydrogen. Other chemicals derived from oil: Alcohols Ethane Ethanol Homologous series: know first 3 members and recognise –OH group in others

  20. Methanol: very important feedstock for the plastics industry Propane-1,2,3-triol (Glycerol): used in the food industry Some examples of alcohols Ethane-1,2-diol (ethylene glycol): used in anti-freeze Cholesterol: an important substance in the body Phenol (carbolic acid): important feedstock for the plastics industry Hexadecan-1-ol (cetyl alcohol): used as an opacifier in shampoo

  21. Important reagents eg. to make esters Why are alcohols important? Less volatile than alkanes Boiling point: 100oC Boiling point: 78oC Boiling point: -89oC Photograph: available at http://en.wikipedia.org/wiki/File:Lilit.jpg Important solvents Useful fuels Photograph: by Luftfahrrad, available at http://en.wikipedia.org/wiki/File:Saab_9-3_SportCombi_1.8t_BioPower_Facelift_rear.JPG

  22. Obtaining ethanol 1. Main manufacture is by fermentation (bio-ethanol) C6H12O6 → 2 C2H5OH + 2 CO2 2. Secondary manufacture by reaction of ethene with steam (synthetic ethanol) C2H4 + H2O → CH3CH2OH Phosphoric acid is used as a catalyst, absorbed on a porous material Factors affecting the choice of method: Land space, climate, oil reserves

  23. Properties of alcohols • Chemical reactions (compare with water) pH, combustion, with sodium RSC practical guide ECARBON5 • Oxidation RSC practical guide ECARBON4 (quite advanced) • Dehydration Use same apparatus and method as for cracking. Aluminium oxide Mineral wool soaked in ethanol

  24. Other chemicals derived from oil:Carboxylic acids Homologous series – know first members and recognise -COOH Why are they acidic? RCOOH(l) + H2O(l) RCOO-(aq) + H3O+(aq) Carboxylic acid molecule Carboxylate anion

  25. Methanoic acid (Formic acid): Present in ant stings Some examples of carboxylic acids Ethanoic acid (acetic acid): Present in vinegar Ethanedioic acid (oxalic acid): Present in rhubarb Prop-2-enoic acid (acrylic acid): Used to make polymers Propanoic acid: Used to make preservatives for food 2-hydroxybenzoic acid (salicyclic acid): Used in pharmaceutical products

  26. For making polymers Why are carboxylic acids important? They are weak acids RCOOH(l) + H2O(l)⇌ RCOO-(aq) + H3O+(aq) Important in the food industry For making pharmaceuticals

  27. Properties of ethanoic acid RSC practical guide ECARBON6 Compares ethanoic and hydrochloric acids of equal concentration Good link between topics

  28. Other chemicals derived from oil:Esters RSC practical guide ECARBON3 Safety – conc. sulfuric acid. Pre-dose test tubes with the acid Alcohol + Carboxylic acid Ester + water Simple esters are sweet smelling compounds. Fats and oils are triglyceride esters. Ethyl Ethanoate From Ethanol From Ethanoic acid

  29. Ethyl acrylate: Used in paint Some examples of esters Cellulose acetate: Used to make films and lacquers Ethyl acetate: a useful solvent Acetyl salicylate: Aspirin Methyl salicylate: Oil of Wintergreen Vinyl acetate: Used to make polyvinyl acetate

  30. PET bottles PET is polyethylene terephthalate a polyester PET bottles can be recycled into new bottles (about 20% of a new bottle) carpets and fleeces

  31. Soaps and Detergents Soaps made by heating a fat or oil with concentrated sodium hydroxide solution Fats and oils are triglycerides. Fats – solids – saturated hydrocarbon chains Oils – liquids – unsaturated (double bonds in chain) will decolourise bromine water. Add H2 across double bonds to make margarine – nickel catalyst and high pressure.

  32. Making soap The sodium hydroxide splits up (hydrolyses) the triglyceride regenerating glycerol (propan-1,2,3–triol) and sodium salts of the long chain acids. Soaps are the sodium salts of long chain carboxylic acids See worksheets: ‘Making Soap’ & ‘Making Soaps and Detergents’

  33. Want more on Soaps & Detergents? Only applicable to certain specifications. If you’d like more on detergents, micelles, liposomes and the language associated with water and fat loving/hating species let me know.

  34. That’s it for now …. What for next term? Some physics? Which topics?

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