1. Extraction of metals
Only some unreactive metals such as silver, gold and platinum can occur freely in nature. Most metals react with other elements to form ores.

2. Major steps in extraction of metal
Ore concentration
Ore is purified and concentrated, unwanted rocks removed
Reduction to crude metal
Metal oxides to be reduced to metals, resulting in a mixture of metals collected
Refining to obtain pure metal
To obtain a specific metal, purify and remove unwanted metal impurities

3. the extraction of metals
Method of extraction depends on the position of the metal in the reactivity series.
extraction of metal involves:
getting rid of the unwanted rock to obtain concentrated form of the mineral
obtaining pure metal from the mineral by chemical reactions

4. the extraction of metals
Metals at the top of the reactivity series are very reactive:
bonds in their compounds are very strong
must be extracted by decomposing their compounds with electricity in an expensive process called electrolysis
aluminium is extracted from aluminium oxide by passing an electric current through it
2Al2O Al + 3O2

5. Ways of Extraction Potassium K
Sodium Na
Calcium Ca
Magnesium Mg
Aluminium Al
Zinc Zn
Iron Fe
Tin Sn
Lead Pb
Copper Cu
Mercury Hg
Silver Ag
Gold Au
Platinum Pt
Extracted by electrolysis of molten chlorides
Extraction by electrolysis of molten Al2O3 dissolved in cryolite
Extraction by reduction of oxides using carbon
Roasting ore by heating alone

6. Extraction of Iron

7. Raw materials of extraction of Iron
Iron Ore
eg haematite ore [iron(III) oxide, Fe2O3]
Coke
carbon, C
Hot air
for the O2 in it
Limestone
calcium carbonate, CaCO3

8. Stage 1 – Production of carbon dioxide
The coke is ignited at the base and hot air blown in to burn the coke (carbon) to form carbon dioxide
C(s) + O2(g)  CO2(g)
The limestone is decomposed by heat to produce carbon dioxide & quicklime
CaCO3(s)  CaO(s) + CO2(g)

9. Stage 2 – Production of carbon monoxide
At high temperature, the carbon dioxide formed reacts with more coke (carbon) to form carbon monoxide
CO2(g) + C(s)  2CO(g)

10. Stage 3 – Reduction of haematite
The carbon monoxide removes the oxygen from the iron oxide ore.
This frees the iron, which is molten at the high blast furnace temperature, and flows down to the base of the blast furnace.
Fe2O3(s) + 3CO(g)  2Fe(l) + 3CO2(g)
Other possible ore reduction reactions are ...
Fe2O3(s) + 3C(s)  2Fe(l) + 3CO(g)
2Fe2O3 (s) + 3C(s)  4Fe(l) + 3CO2 (g)

11. Stage 3 – Reduction of haematite
Waste gases escape through the top of the furnace
Eg. Carbon monoxide, carbon dioxide, nitrogen…

12. Stage 4 – Removal of Impurities
The original ore contains silica (SiO2, silicon dioxide). These react with limestone to form a molten slag of e.g. calcium silicate in 2 stages
CaCO3  CaO + CO2
CaO + SiO2  CaSiO3
The molten slag forms a layer above the more dense molten iron and can be separately, and regularly, drained away. The iron is cooled and cast into pig iron ingots / transferred directly to a steel producing furnace
Slag can be used for road surfacing

14. Why Steel?
Steel is iron that has most of the impurities removed. Steel also has a consistent concentration of carbon throughout (0.5 percent to 1.5 percent)
Impurities like silica, phosphorous and sulphur weaken steel tremendously, so they must be eliminated
The advantage of steel over iron is greatly improved strength

15. Pig Iron to Steel Using Basic Oxygen Furnace
Pear-shaped furnace, lined with refractory bricks, that refines molten iron from the blast furnace and scrap into steel
Scrap is dumped into the furnace vessel
Followed by the hot metal from the blast furnace.
A high-pressure stream of oxygen is blown into it to cause chemical reactions that separate impurities as fumes or slag
Once refined, the liquid steel and slag are poured into separate containers

18. Types of Steel Steel Percentage of carbon Mild carbon steel
Up to 0.25%
High carbon steel
0.45% %
Stainless steel – alloy
Little carbon, with chromium & nickel

19. Properties of Steel Can be changed by the use of controlled additives
Eg. Carbon, chromium, nickel, manganese, silicon etc…

20. Uses of Steel Steel Uses Mild carbon steel – strong, hard & malleable
Make steel parts in car bodies , machineries
High carbon steel – strong but brittle
Make knives, hammer, cutting tools
Stainless steel – does not rust
Pipes & tanks in chemical plants, making cutlery, surgical instruments

21. Alloy Mixture of a metal with other elements
Element in the largest proportion is the base metal
Elements in smaller proportions are the alloying elements

23. Metals
Soft
Low resistance to corrosion
High m.p
Easy to shape

24. Alloys
Have different physical properties compared to their constituent elements
Produce mainly for:
Improving strength and hardness
Improving resistance towards corrosion
Improving appearance of metal
Lower m.p of metal

25. Extraction of Aluminium from Bauxite
Raw materials
Bauxite: ore containing hydrated aluminium oxide Al2O3.2H2O
M.p: ~2000C
Molten Cryolite aka sodium aluminium fluoride Na3AlF6
used to lower m.p to ~900C
Carbon electrodes

26. Extraction of Aluminium
Cryolite is added to lower the melting point & to dissolve the ore & bauxite ore of aluminium oxide is continuously added
When p.d is applied,
Al3+ is attracted to the negative cathode
O2- is attracted to the positive anode

27. Extraction of Aluminium
At the cathode,
Al3+ gains 3 electrons from the cathode to form molten aluminium, which is tapped off
Al3+(l) + 3e-  Al (l)
At the anode,
O2- loses 2 electrons to the anode to form oxygen
2O2-(l)  O2(g) + 4e-
Oxygen released attacks carbon anode, to form Carbon monoxide/dioxide. Carbon anode dissolved. Needs to be replaced regularly

29. Anodising
Form of electroplating using oxygen, used commonly for aluminium
Aluminium when exposed in air forms a thin protective coat of aluminium oxide
For better protection, a thicker coat is made
Through the process: Anodising

30. Anodising Make aluminium the anode in sulphuric acid bath
Oxygen produced at the anode then combines with aluminium to form a protective porous layer aluminium oxide 1000 times thicker, compared when exposed to air
Pores can be sealed by dipping into hot water or coloured by using dyes which can be absorbed into it

31. Uses of Aluminium Uses Properties Overhead electric cables
Low density, light
Resistant to corrosion (protected by aluminium oxide)
Good electrical conductivity
Food containers
Non-toxic
Resistant to corrosion
Good conductor of heat
Aircraft body
High tensile strength

32. Conditions for Corrosion of Iron
Presence of oxygen
Presence of water
Presence of sodium chloride/acidic pollutants speed up rusting
Rusting is an exothermic redox reaction where iron is oxidized to form hydrated iron(III) oxide
4Fe(s) + 3O2(g) +
2xH2O(l)
 2Fe2O3.xH2O (s)

33. Prevention of rusting Use of protective layer
Painting – Used in cars, ships, bridges
Greasing – Tools & machine parts
Zinc plating(Galvanising) – Zinc roofs
Tin plating – Food cans
Creates barrier around the metal preventing contact with oxygen and water

34. Sacrificial protection
More reactive metal, eg, Magnesium or zinc is attached to iron or steel
Protects by sacrificing itself, corrodes first since it is more reactive
Iron will not rust in the presence of a more reactive metal
Used in underground pipes, ships, steel piers

35. Alloying Addition of nickel and chromium to iron
Chromium (III) oxide Cr2O3 on the surface protects iron from corrosion
Used in cutlery, surgical instruments, pipes & tanks in chemical plants

36. Finite Resource Metal ores – finite resource, will be used up
Need to recycle metals
Save resources and solves litter disposal
Saves energy
Saves costs