Non-Metals

1. Non-Metals Prepared December 2007 Alrick Moodie

2. What are non-metals ? • Non-metals are those substances which are not metals i.e. they do not ionize by electron loss and do not show the characteristics of metals

3. Properties of Non-Metals • Poor conductors of heat and electricity • Brittle , not malleable and ductile • Dull in colour • Low in sonority

4. Chemical Properties • React with air/oxygen to give covalent acidic oxides ( although a few give neutral oxides e.g. CO ) • React with metals to form ionic compounds • Do not react with dilute acids • Do not react with water except chlorine • Tend to be oxidizing agents

5. Common Non-metals We will be looking at : • Hydrogen • Chlorine • Oxygen • Carbon • Sulphur • Nitrogen

6. Hydrogen It is a diatomic gas H2 It is colourless and odourless . It is almost insoluble in water and is the lightest known substance .

7. Chemical Properties of Hydrogen • It has a neutral pH • It burns in air/oxygen • It combines with reactive metals to give hydrides : Mg + H2 MgH2 • It can act as a reducing agents e.g. in the extraction of metals CuO + H2 Cu + H2O

8. Uses of Hydrogen • Manufacture of ammonia , nitric acid and nylon • Manufacture of margarine and other hydrogenated oils • In welding • As fuel

9. Laboratory Preparation • Hydrogen can be prepared by reacting an acid with a metal Zn + 2HCl  ZnCl2 + H2

10. Diagram of the Laboratory Preparation of Hydrogen

11. The Water Cycle

13. Water vapour in the atmosphere condenses and form water droplets and precipitation occurs . If temperature is low we will get snow or hail ( ice ) . The water on the ground : • percolates and go underground • runs off into rivers and the seas • evaporates

14. Plants absorb water and loses it through a process called transpiration Animals also intake water and lose through excretion ( sweat , urine or breathing )

15. Uses of water • Domestic purposes e.g. drinking , washing , cooking , cleaning • Irrigation of crops • Generation of electricity • Industrial processes • Recreational activities

17. Chlorine

18. Chlorine It is a diatomic gas Cl2 It is a greenish-yellow gas with a choking odour . It is more dense than air and is slightly soluble in water .

19. Chemical Properties of Chlorine • Readily combines with metals to form chlorides : Mg + Cl2 MgCl2 • It is a powerful oxidizing agent • It bleaches substances ( in the presence of moisture )

20. Uses of Chlorine • Manufacture of plastics e.g. PVC • Sterilize water e.g. drinking supplies , swimming pools • Preparation of cleaning fluids and bleaching agents • Manufacture of hydrochloric acid

21. Laboratory Preparation • Chlorine can be the oxidation of conc. Hydrochloric acid by potassium manganate VII HCl (l) + KMnO4(s)  KCl (aq) + MnCl2 (aq) + H2O (l) + Cl2 (g)

23. Oxygen

24. Oxygen is the most abundant element on Earth . Approximately 50% of the earth’s crust is composed of oxygen containing compounds , while 20% of the atmosphere is free oxygen gas .

25. Oxygen is a diatomic gas O2 although in the upper atmosphere it exists in the allotrope form as ozone O3 . It is a colourless odourless gas which is slightly soluble in water and has the same density as air .

26. Chemical Properties • It has a neutral pH of 7 • Supports combustion • Combines with most elements to form oxides • It is involved in biological processes of respiration .

27. Uses of Oxygen • In welding apparatus • Rocket fuels • Steel manufacture • Breathing equipment

28. Laboratory Preparation Oxygen is prepared by the catalytic decomposition of hydrogen peroxide . 2H2O2 (aq)  2H2O (l) + O2 (g) MnO2 is the catalyst used

30. Carbon

31. Carbon exists as many natural occurring allotropes ; diamond , graphite , charcoal and coke .

33. Chemical Properties of Carbon • Readily burns in oxygen to form carbon dioxide . In limited supply of air carbon monoxide is formed . • It is a powerful reducing agent at high temperatures .

34. Carbon Dioxide Carbon dioxide is a colourless , odourless gas which is slightly soluble in water . It is more dense than air and is slightly acidic . The presence of carbon dioxide can be determined by the formation of a precipitate with calcium hydroxide .

35. Preparation Carbon dioxide is prepared by the reaction of a carbonate and a dilute acid .

37. Uses of Carbon dioxide • As a refrigerant • As a fire suppressant • In sodas

38. Carbon cycle

39. Sulphur

40. Sulphur is found in the earth’s crust as a free element and as sulphides and sulphates . The free sulphur occurs as two allotropes , monoclinic and rhombic .

41. Chemical Properties • Burns in air to form sulphur dioxide • Combines with most metals to form sulphides .

42. Uses • Manufacture of sulphuric acid • Manufacture of gunpowder and matches • Manufacture of fungicides and pesticides • Vulcanization of rubber

43. Sulphur is obtained by the Frasch process where the sulphur is mined directly from the earth in its elemental form .

44. Sulphuric acid

45. Concentrated sulphuric acid is a colourless , odourless , oily liquid . It is a powerful dehydrating liquid . Diluting conc. sulphuric acid is a very exothermic reaction and must be done cautiously .

46. Uses • Manufacture of fertilizers • Manufacture of white paint • Manufacture of soaps and detergents • Refining of petroleum • Vulcanization

47. Manufacture Sulphuric acid is manufactured by the Contact process which has three stages . • Sulphur is burned in air to form sulphur dioxide S (s) + O2 (g)  SO2 (g) • The sulphur dioxide is oxidized to sulphur trioxide 2SO2 (g) + O2 (g)  2SO3 (g)

48. The sulphur trioxide is dissolved in concentrated sulphuric acid to form oleum which is diluted to form sulphuric acid . H2SO4 (aq) + SO3 (g)  H2S2O7 (l) H2S2O7 (l) + H2O (l)  2H2SO4 (aq)

50. Nitrogen