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metals

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  • 1. METALS
    • Properties of Metals
    • Extraction of Metals
    • Uses of Metals
  • 2. Metals: What are Metals?
    • It’s rather hard to imagine a world without metals.
    • Look around you – the chairs you’re sitting on have metal frames; the cutlery you use during recess is made of steel (an alloy of iron); the wires in your MP3 player are made of copper, another metal
    • What exactly are metals and what makes them suitable for the uses which we put them to?
  • 3. Metals: Physical Properties
    • Metals are malleable
      • They can be bent into many shapes.
    • Metals are ductile
      • They can be drawn in thin wires.
    • Metals are good conductors of electricity
      • They are made into wires and various electrical goods like lamps, etc.
  • 4. Metals: Physical Properties
    • Metals are good conductors of heat
      • They are made into heating coils and cooking instruments like woks and pans.
    • Metals have high melting and boiling points
      • They are made into filaments of lamps which can glow white hot and still not melt i.e. tungsten
      • Exception: Mercury – The only liquid metal
  • 5. Metals: What is an Alloy?
    • An alloy is a mixture of 2 or more metallic elements e.g. brass, pewter
    • Some even contain non-metallic elements e.g. steel
    • Alloys are stronger and harder than pure metals. Why?
  • 6. Metals: What is an Alloy?
    • Pure metals are too soft because the layers of atoms can slide over each other easily
  • 7. Metals: What is an Alloy?
    • In an alloy, atoms of different metals are of different sizes.
    • This disrupts the orderly layers of atoms and makes it much harder for the layers to slide over each other.
  • 8. Metals: What is an Alloy?
    • Only small quantities of other elements need to be added to make a pure metal stronger and harder.
    • Most metals used are alloys, because they are tougher and stronger.
    DURALUMIN Copper + Aluminium BRASS Copper + Zinc BRONZE Copper + Tin/Aluminium
  • 9. Metals: Chemical Properties
    • Reaction with Water
      • Metals react with water in varying degrees of intensity, to produce a metal hydroxide and hydrogen gas [ VIDEO ]
    Sodium + Water
  • 10. Metals: Chemical Properties
    • Reaction with Hydrochloric Acid
      • Metals also react with hydrochloric acid in varying degrees of intensity to produce a metal chloride and hydrogen gas
  • 11. Metals: The Reactivity Series
    • Not all metals react the same way
      • Some react vigorously fast; others react slowly, some don’t react at all
    • Metals can be listed in order of reactivity
      • The Reactivity Series
      • The most reactive metal is at the top
  • 12. Metals: The Reactivity Series
    • A metal high in the series
      • Reacts vigorously and quickly with chemicals
      • Corrodes easily
    • A metal low in the series
      • Does not react vigorously with chemicals
      • Does not corrode easily
    Au Ag Cu [H] Pb Sn Fe Zn Al Mg Ca Na K Least Reactive Most Reactive
  • 13. Metals: Rusting of Iron & Steel
    • Corrosion of iron and steel in air  rusting
    • Iron + Oxygen  Iron (III) oxide
    • 2Fe + 3O 2  Fe 2 O 3
    • Conditions
      • Presence of water (moisture)
      • Presence of oxygen (air)
  • 14. Metals: Prevention of Rusting
    • Coating with layer of another substance, stopping air/water from reaching the iron/steel underneath
      • Paint (cars)
      • Oil/Grease (machinery; aids in lubrication)
      • Once breached, rusting will still occur
  • 15. Metals: Prevention of Rusting
    • Coating with another metal which corrodes in place  Sacrificial protection
      • Zinc (Galvanising; prevent rusting of ship hulls)
      • Magnesium (prevent rusting of undersea steel pipes)
      • Metal will rust in place even if coating layer is breached
  • 16. Metals: Prevention of Rusting Aesthetically pleasing because chromium is shiny Chromium plating Canned food Tin plating Machinery; aids in lubrication Covering with grease/oil Large iron and steel pipes e.g. cars, bridges, ships Covering with paint Use Method
  • 17. Metals: Prevention of Rusting Corrugated iron sheets for roofing Galvanising Cutlery, medical instruments, kitchen sinks, etc Alloy (Steel) Underground steel pipes Magnesium blocks Steel hulls of ships Zinc blocks Use Method
  • 18. Metals: The Extraction of Metals
    • Metals seldom occur in nature in their pure form  commonly found as ores (ionic compounds of the metal + a non-metal)
      • Bauxite (aluminium)
      • Cassiterite (tin)
      • Galena (lead)
      • Haematite (iron)
  • 19. Metals: The Extraction of Metals
    • The rock is first removed from the mineral and the mineral is then purified via chemical means
      • Very reactive metals (electrolysis)
        • E.g Aluminium
      • Moderately reactive metals (heated with other compounds)
        • E.g. Iron
      • Unreactive metals (found uncombined)
        • E.g. gold
  • 20. Metals: The Extraction of Iron
    • Iron ore  haematite
    • Extraction process occurs in a blast furnace where temperatures can reach over 1600 °C
  • 21. Metals: The Extraction of Iron
  • 22. Metals: The Extraction of Iron
    • Coke (carbon) reacts with oxygen (air) to form carbon dioxide & heat
    C (s) + O 2 (g)  CO 2 (g)
  • 23. Metals: The Extraction of Iron
    • Carbon dioxide reacts with more coke to form carbon monoxide .
    C (s) + CO 2 (g)  2CO (g)
  • 24. Metals: The Extraction of Iron
    • Carbon monoxide reacts with iron (III) oxide to produce molten iron .
    Fe 2 O 3 (l) + 3CO (g)  2Fe (l) + 3CO 2 (g)
  • 25. Metals: The Extraction of Iron
    • Limestone decomposes in heat to produce calcium oxide and carbon dioxide .
    CaCO 3 (s)  CO 2 (g) + CaO (s)
  • 26. Metals: The Extraction of Iron
    • Impurities are present in the molten iron i.e. silicon , sulphur & phosphorus . Silicon is found as silicon dioxide (acidic) which reacts with calcium oxide (basic) to form calcium silicate (slag).
    CaO (s) + SiO 2 (s)  CaSiO 3 (l)
  • 27. Metals: Recycling
    • Metals are a non-renewable resource  Will not last forever
      • Alternatives?
        • Making use of other metals in place
        • Recycling
  • 28. Metals: Recycling
    • Why Recycle?
      • Saves cost of metal extraction from ores
      • Prevents unsightly dumping of unwanted iron/steel
      • Prevents the leaching of harmful heavy metals into soil
      • Disadvantage : Recycling metals can sometimes be polluting.
  • 29. Metals: Recycling