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iGCSE chemistry Section 3 lesson 2

iGCSE chemistry Section 3 lesson 2. Content. The iGCSE Chemistry course. Section 1 Principles of Chemistry Section 2 Chemistry of the Elements Section 3 Organic Chemistry Section 4 Physical Chemistry Section 5 Chemistry in Society. Content. Section 3 Organic Chemistry.

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iGCSE chemistry Section 3 lesson 2

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  1. iGCSE chemistrySection 3 lesson 2

  2. Content The iGCSE Chemistry course Section 1 Principles of Chemistry Section 2 Chemistry of the Elements Section 3 Organic Chemistry Section 4 Physical Chemistry Section 5 Chemistry in Society

  3. Content Section 3 Organic Chemistry • Introduction • Alkanes • Alkenes • Ethanol

  4. c) Alkenes 3.6 recall that alkenes have the general formula CnH2n 3.7 draw displayed formulae for alkenes with up to four carbon atoms in a molecule, and name the straight-chain isomers (knowledge of cis- and transisomers is not required) 3.8 describe the addition reaction of alkenes with bromine, including the decolourising of bromine water as a test for alkenes. d) Ethanol 3.9 describe the manufacture of ethanol by passing ethene and steam over a phosphoric acid catalyst at a temperature of about 300°C and a pressure of about 60–70 atm 3.10 describe the manufacture of ethanol by the fermentation of sugars, for example glucose, at a temperature of about 30°C 3.11 evaluate the factors relevant to the choice of method used in the manufacture of ethanol, for example the relative availability of sugar cane and crude oil 3.12 describe the dehydration of ethanol to ethene, using aluminium oxide. Lesson 2 c) Alkenes d) Alcohols

  5. Organic Chemistry It’s the chemistry of carbon-containing compounds

  6. Hydrocarbon = compound containing hydrogen and carbon only

  7. The alkanes are saturated hydrocarbons – they form single covalent bonds only

  8. The alkanes have the general formula of CnH2n+2

  9. Compounds exhibit isomerism when they have the same molecular formula but different structural formulae.

  10. Alkenes X X C X X X X

  11. Alkenes X X X X C C X X X X X X X X

  12. Alkenes X X X X C C X X X X X X X X

  13. Alkenes X X X X C C X X X X X X X X Ethane

  14. Alkenes X X X X C C X X X X X X X X

  15. Alkenes X X X X C C X X X X H H X X X X C C Ethene H H

  16. Alkenes X X X X C C X X X X H H X X X X C C Ethene H H Double bond

  17. Alkenes X X X X C C X X X X H H Alkenes are known as unsaturated hydrocarbons because they contain a double bond. X X X X C C Ethene H H Double bond

  18. Alkenes X X X X C C X X X X H H Alkenes are known as unsaturated hydrocarbons because they contain a double bond. Alkenes form a homologous series with the general formula CnH2n X X X X C C H H Double bond

  19. Alkenes

  20. Alkenes H H C C H H

  21. Alkenes H H C C H H H H H C C C H H H

  22. Alkenes H H C C H H H H H C C C H H H

  23. Alkenes H H C C H H H H H C C C H H H

  24. Chemical properties of alkenes

  25. Chemical properties of alkenes 1. Alkenes are generally more reactive than alkanes.

  26. Chemical properties of alkenes • Alkenes are generally more reactive than alkanes. • Ethene burns with a smoky flame. This is because it contains a relatively high percentage of carbon: • C2H4 + 3O2 2CO2 + 2H2O • Other alkenes do not burn with a smoky flame

  27. Chemical properties of alkenes 3. Alkenes and unsaturated compounds undergo addition reactions.

  28. Chemical properties of alkenes 3. Alkenes and unsaturated compounds undergo addition reactions. An addition reaction is one in which two molecules combine to form a single molecule.

  29. Chemical properties of alkenes • Alkenes and unsaturated compounds undergo addition reactions. • For example: alkenes react with bromine to form 1,2-dibromoethane: • H H H H • C C + Br Br  H C C H • H H Br Br

  30. Chemical properties of alkenes • Alkenes and unsaturated compounds undergo addition reactions. • For example: alkenes react with bromine to form 1,2-dibromoethane: • H H H H • C C + Br Br  H C C H • H H Br Br Test for an alkene. Alkenes will decolourise bromine water as the alkene reacts with it. Eg. Ethene + Bromine Water  Colourless solution (colourless) (yellow-brown)

  31. Ethanol

  32. Ethanol Ethanol belongs to the group of organic compounds known as the alcohols.

  33. Ethanol Ethanol belongs to the group of organic compounds known as the alcohols. Alcohols contain the hydroxyl group, -OH

  34. Ethanol Ethanol belongs to the group of organic compounds known as the alcohols. Alcohols contain the hydroxyl group, -OH The alcohols form a homologous series with the general formula CnH2n+1OH

  35. Ethanol Ethanol belongs to the group of organic compounds known as the alcohols. Alcohols contain the hydroxyl group, -OH The alcohols form a homologous series with the general formula CnH2n+1OH Eg. Ethanol C2H5OH H H H C C O H H H

  36. Manufacture of Ethanol

  37. Manufacture of Ethanol • Ethanol may be produced in two ways: • Industrial preparation • Ethanol is made on a large scale by the hydration of ethene at a temperature of 300oC and a pressure of about 65 atmospheres.

  38. Manufacture of Ethanol • Ethanol may be produced in two ways: • Industrial preparation • Ethanol is made on a large scale by the hydration of ethene at a temperature of 300oC and a pressure of about 65 atmospheres. A hydration reaction is a chemical reaction in which the hydroxyl group (-OH) and a proton (H+) are added to a compound

  39. Manufacture of Ethanol • Ethanol may be produced in two ways: • Industrial preparation • Ethanol is made on a large scale by the hydration of ethene at a temperature of 300oC and a pressure of about 65 atmospheres. • C2H4(g) + H2O(l) C2H5OH(g) • Phosphoric acid is used as a catalyst.

  40. Manufacture of Ethanol • Ethanol may be produced in two ways: • Preparation by fermentation • Sugars are carbohydrates which can be broken down in the presence of yeast to form ethanol and carbon dioxide.

  41. Manufacture of Ethanol • Ethanol may be produced in two ways: • Preparation by fermentation • Sugars are carbohydrates which can be broken down in the presence of yeast to form ethanol and carbon dioxide. Oil layer Lime water Yeast in glucose solution

  42. Manufacture of Ethanol • Ethanol may be produced in two ways: • Preparation by fermentation • Sugars are carbohydrates which can be broken down in the presence of yeast to form ethanol and carbon dioxide. C6H12O6  2C2H5OH + 2CO2 sugar ethanol Oil layer Lime water Yeast in glucose solution

  43. Manufacture of Ethanol • Ethanol may be produced in two ways: • Preparation by fermentation • Sugars are carbohydrates which can be broken down in the presence of yeast to form ethanol and carbon dioxide. C6H12O6  2C2H5OH + 2CO2 sugar ethanol Oil layer This process is known as fermentation Lime water Yeast in glucose solution

  44. Manufacture of Ethanol • Ethanol may be produced in two ways: • Preparation by fermentation • Sugars are carbohydrates which can be broken down in the presence of yeast to form ethanol and carbon dioxide. Fermentation is used in wine and beer making. The reaction is carried out at a temperature of about 30oC. The reaction is known as anaerobic respiration as air must be excluded. C6H12O6  2C2H5OH + 2CO2 sugar ethanol Oil layer This process is known as fermentation Lime water Yeast in glucose solution

  45. Manufacture of Ethanol • Ethanol may be produced in two ways: • Preparation by fermentation • Sugars are carbohydrates which can be broken down in the presence of yeast to form ethanol and carbon dioxide. Fermentation is used in wine and beer making. The reaction is carried out at a temperature of about 20oC. The reaction is known as anaerobic respiration as air must be excluded. If air does come into contact with the wine, the wine becomes sour due to the oxidation of ethanol to ethanoic acid. Vinegar means ‘bad wine’ and it contains ethanoic acid. Bacteria in the air may also kill the yeast. C6H12O6  2C2H5OH + 2CO2 sugar ethanol Oil layer This process is known as fermentation Lime water Yeast in glucose solution

  46. Manufacture of Ethanol • Ethanol may be produced in two ways: • Preparation by fermentation • Sugars are carbohydrates which can be broken down in the presence of yeast to form ethanol and carbon dioxide. C6H12O6  2C2H5OH + 2CO2 sugar ethanol Oil layer This process is known as fermentation. The reaction requires an enzyme in yeast (zymase) Lime water Yeast in glucose solution

  47. Manufacture of Ethanol • Ethanol may be produced in two ways: • Preparation by fermentation • Sugars are carbohydrates which can be broken down in the presence of yeast to form ethanol and carbon dioxide. C6H12O6  2C2H5OH + 2CO2 sugar ethanol Oil layer The yeast eventually dies when the alcohol content reaches about 15% or when the sugar is used up Lime water Yeast in glucose solution

  48. Manufacture of Ethanol Industrial preparation Which method? Preparation by fermentation

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