o C1.1 State the main sources of iron.
§ Iron ore (mainly, or
· magnetite Fe3O4
· hematite Fe2O3
· hydrated oxides such as FeOH.OH
· Iron Sulfides FeS2
§ Scrap iron
· magnetite Fe3O4
· hematite Fe2O3
· hydrated oxides such as FeOH.OH
· Iron Sulfides FeS2
§ Scrap iron
o C1.2 Describe and explain the reactions that occur in the blast furnace
§ What happens in the blast furnace is that the iron ores and scrap iron is dropped at the top of the blas furnace and the reducing gases are heated at the bottom of the blast furnace so they rise and react with the iron ores to from iron.
§ The main reactions that occur to get Fe alone are the following
· Fe2O3(s) + 3CO(g)→2Fe(l) + 3CO2(g)
· Fe3O4(s) + 4H2 (g)→3Fe(l) + 4H2O(g)
· FeO(s) + CO(g)→Fe(l) + CO2(g)
· Fe2O3(s) + 3C(s)→2Fe(l) + 3CO(g)
§ We can see that the reducing agents in these reactions are CO, H2, and C. This is how they get these reducing agents
· Coke burns to form carbon monoxide
o 2C(s) + O2(g) → 2CO(g)
· Incomplete combustion of hydrocarbons
o CH4(g) + ½ O2(g) → CO(g) + 2H2(g)
· Carbon dioxide reacts with carbon to form carbon monoxide
o CO2(g) + C(s) → 2CO(g)
· Coke can react with water vapor to produce even more carbon monoxide and hydrogen
o H2O(g) + C(s) → H2(g) + CO(g)
§ To clean the impurities (Si) the following reactions are done
· At high temperatures the limestone decomposes
o CaCO3(s) → CaO(s) + CO2(g)
· Later the CaO reacts with the impurities at high temperatures to form a complex aluminosilicate ‘slag’ that also contains many sulfur impurities
o CaO(s) + SiO2(s) → CaSiO3(l)
§ Pig iron is made from this process
§ The main reactions that occur to get Fe alone are the following
· Fe2O3(s) + 3CO(g)→2Fe(l) + 3CO2(g)
· Fe3O4(s) + 4H2 (g)→3Fe(l) + 4H2O(g)
· FeO(s) + CO(g)→Fe(l) + CO2(g)
· Fe2O3(s) + 3C(s)→2Fe(l) + 3CO(g)
§ We can see that the reducing agents in these reactions are CO, H2, and C. This is how they get these reducing agents
· Coke burns to form carbon monoxide
o 2C(s) + O2(g) → 2CO(g)
· Incomplete combustion of hydrocarbons
o CH4(g) + ½ O2(g) → CO(g) + 2H2(g)
· Carbon dioxide reacts with carbon to form carbon monoxide
o CO2(g) + C(s) → 2CO(g)
· Coke can react with water vapor to produce even more carbon monoxide and hydrogen
o H2O(g) + C(s) → H2(g) + CO(g)
§ To clean the impurities (Si) the following reactions are done
· At high temperatures the limestone decomposes
o CaCO3(s) → CaO(s) + CO2(g)
· Later the CaO reacts with the impurities at high temperatures to form a complex aluminosilicate ‘slag’ that also contains many sulfur impurities
o CaO(s) + SiO2(s) → CaSiO3(l)
§ Pig iron is made from this process
o C1.3 Describe and explain the conversion from iron to steel using the basic oxygen converter
§ Most steel is made from the basic oxygen process. Pre heated oxygen is injected at high pressure into the vessel where pig iron is and the impurities are oxidized.
· C + O2 → CO2
· P4 + 5O2 → P4O10
· Si + O2 → SiO2
§ Apart from CO2 the impurities react with lime to form slag. The dissolved oxygen in the steel is removed by adding controlled amounts of aluminium or silicon before the steel is suitable for casting or rolling. Other elements such as chromium and nickel are added to make different alloys.
· C + O2 → CO2
· P4 + 5O2 → P4O10
· Si + O2 → SiO2
§ Apart from CO2 the impurities react with lime to form slag. The dissolved oxygen in the steel is removed by adding controlled amounts of aluminium or silicon before the steel is suitable for casting or rolling. Other elements such as chromium and nickel are added to make different alloys.
o C1.4 Describe alloys as a homogeneous mixture of metals or a mixture metal and non-metal
§ Homogeneous means from the same part of the periodic table (metal with metal and non metal with non metal. Transition metals often form alloys with each other as their atoms have similar atomic radii and the crystal structure is not seriously disrupted. The addition of other elements into the metallic structure can alter the physical properties.
o C1.5 Explain how alloying can modify the properties of metals
§ Properties such as density, electrical conductivity may not differ that much from their constituents but others such as melting point and tensile strength may vary a lot.
§ For example, solder, an alloy of tin and lead, is a good conductor of electricity but has lower melting point that either of its constituent elements.
§ Steel is an alloy of iron, carbon and other metallic and non-metallic elements and those different metals can be varied in amount to change the chemical and physical properties of steel according to however you want it.
· For example, if you want stainless steel you would need a lot more chromium which increases resistance of steel to corrosion.
· Other steels need to be harder so instead they add molybdenum
§ For example, solder, an alloy of tin and lead, is a good conductor of electricity but has lower melting point that either of its constituent elements.
§ Steel is an alloy of iron, carbon and other metallic and non-metallic elements and those different metals can be varied in amount to change the chemical and physical properties of steel according to however you want it.
· For example, if you want stainless steel you would need a lot more chromium which increases resistance of steel to corrosion.
· Other steels need to be harder so instead they add molybdenum
C1.6 Describe the effects of heat treatment of steel
§ The mechanical properties of steel are affected by heat treatment. It does not alter the shape of the steel, only their structure. The three different types are:
· Tempering – Used when they want to make the steel less brittle and they do so by heating the steel to 400°- 600°C and allowing it to COOL SLOWLY
· Annealing – Used when they want to make the steel more ductile and they do so by heating the steel to a higher temperature (about 1040°C) and then having SLOW COOLING
· Quenching – If they want hard steel in the other hand they use this process which is the same as annealing but instead of cooling slowly they quench it by RAPID COOLING.
· Tempering – Used when they want to make the steel less brittle and they do so by heating the steel to 400°- 600°C and allowing it to COOL SLOWLY
· Annealing – Used when they want to make the steel more ductile and they do so by heating the steel to a higher temperature (about 1040°C) and then having SLOW COOLING
· Quenching – If they want hard steel in the other hand they use this process which is the same as annealing but instead of cooling slowly they quench it by RAPID COOLING.
o C1.7 Describe the properties and uses of iron and steel
§ Steel (different alloys)
· used for kitchen knives and sinks by making it stainless
· used for drill bits by making it tougher
§ Iron - The slag left from blast furnace is used
· Road making
· Cement
· Thermal insulation
· Engine cylinder blocks
· used for kitchen knives and sinks by making it stainless
· used for drill bits by making it tougher
§ Iron - The slag left from blast furnace is used
· Road making
· Cement
· Thermal insulation
· Engine cylinder blocks
o C1.8 Describe and Explain the production of Aluminium by electrolysis of alumina in molten cyrolite
§ Aluminium is mainly made by the electrolytic reduction of aluminium oxide. The main ore of aluminium is bauxite. Aluminium is mainly in the form of the hydroxide Al(OH)3 with iron(III) oxide and titanium hydroxide.
§ Impurities are removed by heating powdered bauxite with sodium hydroxide solution. The aluminium hydroxide dissolved since its amphoteric
· Al(OH)3(s)+ NaOH(aq) → NaAlO2 (aq)+ 2H2O(l)
§ After this the aluminate solution is filtered and removed from these impurities and then the reaction is reversed to get Al(OH)3 again. Then it is heated to get aluminium oxide (alumina).
· 2Al(OH)3 → Al2O3(s) + 3H2O (l)
§ In a separate reaction hydrogen fluoride is reacted with aluminate solution followed by sodium carbonate to get cyrolite
· NaAlO2(aq) + 6HF (g) + Na2CO3 (aq)→ Na3AlF6 (s) + 3H2O(l) + CO2(g)
§ The electrolysis of molten alumina takes place in an open-topped steel container lined with graphite. Since Alumina has a melting point of 2045˚C it is mixed with cyrolite which when mixed has a melting point of 950˚C so less energy is needed.
§ The aluminum is produced in the graphite lining which acts as the negative electrode (cathode). Since molten aluminium is denser than cyrolite, it collects at the bottom of the cell where it can be taken out.
§ Impurities are removed by heating powdered bauxite with sodium hydroxide solution. The aluminium hydroxide dissolved since its amphoteric
· Al(OH)3(s)+ NaOH(aq) → NaAlO2 (aq)+ 2H2O(l)
§ After this the aluminate solution is filtered and removed from these impurities and then the reaction is reversed to get Al(OH)3 again. Then it is heated to get aluminium oxide (alumina).
· 2Al(OH)3 → Al2O3(s) + 3H2O (l)
§ In a separate reaction hydrogen fluoride is reacted with aluminate solution followed by sodium carbonate to get cyrolite
· NaAlO2(aq) + 6HF (g) + Na2CO3 (aq)→ Na3AlF6 (s) + 3H2O(l) + CO2(g)
§ The electrolysis of molten alumina takes place in an open-topped steel container lined with graphite. Since Alumina has a melting point of 2045˚C it is mixed with cyrolite which when mixed has a melting point of 950˚C so less energy is needed.
§ The aluminum is produced in the graphite lining which acts as the negative electrode (cathode). Since molten aluminium is denser than cyrolite, it collects at the bottom of the cell where it can be taken out.
o C1.9 Describe the main properties and uses of aluminium and its alloys
§ The aluminum produced from the electrolysis is more than 99% pure with the main impurities being small amounts of iron and silicon.
§ Properties
· Malleable
· Can be shaped easily
· Excellent conductor of heat and electricity
· Lower density than iron and can form alloys stronger than steel
· Resistant to corrosion
· Thickness of oxide layer (layer that prevents corrosion) can be further increased by anodizing the aluminium.
§ Uses
· Transportation
o Superstructures of trans, ships and aero planes
· Construction
o Window frames, doors, roofing
· Power Transmission
o Overhead electricity cables, capacitor foils
· Kitchen Utensils
o Kettles, saucepans
· Packaging
o Drink cans, foil wrapping
· Chemical Industry
o Al(OH)3 – flame retarder, paper making
o Al2(SO4) – flocculent in sewage treatment and to precipitate PO4-
o Al2O3 – catalyst and catalytic support material, abrasive
§ Properties
· Malleable
· Can be shaped easily
· Excellent conductor of heat and electricity
· Lower density than iron and can form alloys stronger than steel
· Resistant to corrosion
· Thickness of oxide layer (layer that prevents corrosion) can be further increased by anodizing the aluminium.
§ Uses
· Transportation
o Superstructures of trans, ships and aero planes
· Construction
o Window frames, doors, roofing
· Power Transmission
o Overhead electricity cables, capacitor foils
· Kitchen Utensils
o Kettles, saucepans
· Packaging
o Drink cans, foil wrapping
· Chemical Industry
o Al(OH)3 – flame retarder, paper making
o Al2(SO4) – flocculent in sewage treatment and to precipitate PO4-
o Al2O3 – catalyst and catalytic support material, abrasive
o C1.10 Discuss the environmental impact of iron and aluminium production
§ Production of aluminium requires very large quantities of energy to produce from the raw materials. A cheap resource of energy is therefore needed and that is why aluminium plants are normal near hydroelectric plants so that power is available or near sources of coal and natural gas.
§ Like in iron, the recycling aluminium is of great importance as that will save a lot of energy, and it will minimize the damage done to the environment.
§ Iron and steel can be easily separated from aluminium using a magnet.
§ The cost of making aluminium from recycled aluminium is really low as it only requires 5% of the energy that would be needed to produce the same amount of aluminium from bauxite through electrolysis.
§ Recycling aluminium reduced global warming since less carbon dioxide is released into the atmosphere
· The carbon dioxide is produced from the oxidized positive electrodes.
§ Like in iron, the recycling aluminium is of great importance as that will save a lot of energy, and it will minimize the damage done to the environment.
§ Iron and steel can be easily separated from aluminium using a magnet.
§ The cost of making aluminium from recycled aluminium is really low as it only requires 5% of the energy that would be needed to produce the same amount of aluminium from bauxite through electrolysis.
§ Recycling aluminium reduced global warming since less carbon dioxide is released into the atmosphere
· The carbon dioxide is produced from the oxidized positive electrodes.
