Production and Uses of Metals

1. Production and Uses of Metals CHEMISTRY 2 Additional Science Chapter 8

2. e.g. gold Pyrite (a mineral of iron - sulphide) Haematite (a mineral of iron - oxide) Iron pan Metals are produced from their ores by a process called reduction. Metallic minerals The least reactive metals occur in an uncombined form within the Earth’s crust. The other metals exist as ores in combination with other elements such as oxygen and sulphur. Additional Science Chapter 8

3. The reactivity series of metals Different metals have different reactivities. A more reactive metal will remove oxygen from the oxide of a less reactive metal when a mixture of the two is heated. When a mixture of powdered aluminium and iron(III) oxide is ignited by a high temperature fuse, molten iron is formed. This reaction is called the thermit reaction and is used to weld sections of railway track. A mixture of aluminium and iron(III) oxide reacting together Additional Science crucible Chapter 8 railway track railway track

4. The reactivity series of metals This table shows the reactivity series of common metals, and how they are extracted from their ores. Additional Science Chapter 8

5. Blasts of hot air Blasts of hot air Molten iron Extracting iron from its oreChemical reduction with carbon 1. Raw materials (iron ore, coke and limestone) are added at the top of the furnace. 2. Blasts of hot air (which give the furnace its name) are blown in near the bottom of the furnace. Load if iron ore, coke and limestone 3. Oxygen in the blasts of air reacts with coke (carbon) to form carbon monoxide. 2C + O2 2CO This reaction is very exothermic and the temperature in the furnace reached 2000°C. Gas outlet The blast furnace 1000°C 4. As the carbon monoxide rises up the furnace, it reacts with the iron ore (iron(III) oxide to form iron. Fe2O3 + 3CO  2Fe + 3CO2 1500°C 5. Molten iron runs to the bottom of the furnace. It is tapped off from time to time. 6. The molten iron is used to make steel or poured into moulds to solidify. The large chunks of iron formed are called ‘pigs’ so this metal is called ‘pig iron’. 2000°C Molten slag (impurities) Outlet for the slag Outlet for molten iron

6. Car bodies Tinplate machines Domestic appliances Creating alloys with other metals Stainless steel (chromium and nickel) Very hard steel (tungsten) Tough steel (manganese) Steel – properties and uses Iron from the blast furnace is very brittle because it contains up to 4.5% carbon. Most of this iron is converted to steel, which is far more useful, by removing most of the carbon. Mild steel contains approximately 0.5% carbon. Hard steel contains up to 1.5% carbon. Additional Science It is possible to treat steel . Chapter 8 Heat treatment

7. Steel is recycled on a large scale. Recycling steel Saves up to 50% of energy costs Helps to conserve iron ore Cuts down the emission of greenhouse gases Additional Science Chapter 8

8. Electrodes Conducting liquid – electrolyte Electrolysis – background Electrolysis is a chemical reaction. Current enters the electrolyte via two solid conductors called electrodes. Additional Science Chapter 8

9. Negative Electrode Positive electrode Electrolyte Electrolysis – background The anode is the positive electrode, and the cathode is the negative electrode. ion+ ion- ion- ion+ Additional Science ion+ ion- ion- ion+ Chapter 8 The positive ions (cations) move towards the negative electrode, and the negative ions (anions) move towards the positive electrodes.

10. Electrolysis – extraction of reactive metals Remove impurities by chemical method Bauxite – a rock containing aluminium Aluminium oxide powder (alumina), with a very high melting point Electrolysis of aluminium oxide (alumina) crust of solidified electrolyte 1. Aluminium oxide is dissolved in molten cryolite (about 950°C). carbon anodes 2. Oxygen gas is formed at the carbon anodes, and at that high temperature the anodes react with oxygen, burning away and having to be replaced from time to time. aluminium oxide in molten cryolite Additional Science Chapter 8 Molten aluminium tap hole 3. Aluminium in the form of a molten metal forms at the cathode. 4. The tap hole is used to collect the aluminium, the crust needs to be broken to add more aluminium oxide. insulated cell casing carbon lining to cell acting as the cathode

11. Al3+ +3e Al 2O2- -4e O2 The equations for the reaction: Positive aluminium ions are attracted to the negative cathode, where they gain electrons and form aluminium metal. Additional Science Negative oxide ions are attracted to the positive anode, where they lose electrons and form oxygen gas. Chapter 8

12. A lot of electricity is required for producing the metal via electrolysis The raw materials and the product need to be transported easily A good transport network in and out Build aluminium works near cheap sources of electricity Port Railway links Roads Hydroelectric Power Source Nuclear Power Station Locating aluminium works Additional Science Chapter 8

13. Properties of aluminium light strong density of 2.7g/cm3 resistant to corrosion layer of aluminium oxide (this prevents corrosion even though the metal is very reactive) Using aluminium Additional Science Chapter 8

14. Properties of copper excellent conductor of electricity and heat malleable ductile non toxic Use of copper Additional Science Chapter 8

15. Properties of titanium good conductor of heat and electricity light strong tough high melting point non toxic low density non corrosive Using titanium Additional Science Chapter 8

16. The consequences of metal extraction Disadvantages Advantages When the ore runs out, the mine workings may be abandoned causing a deterioration of the landscape. Extraction and processing of minerals creates employment. Importing metals is very expensive for the country. Sometimes less useful and toxic metals are found with the ones that are needed. Important for the economy (Economic boom in the UK during Industrial Revolution). Additional Science Fluctuations in the cost of metals can affect the economy. Chapter 8 A lot of electricity is needed to produce aluminium. Processing minerals have a detrimental effect on the environment. Many minerals are sulphides – produce sulphur dioxide (the gas that causes acid rain).