15 Metals


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15 Metals

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