The production and use of metals How can we make metals? Can we use the same method for all metals? Name ____________________________ Class __________ Date __________ Teacher ____________________________ ADDITIONAL BOOKLET 3 1 THE PRODUCTION AND USE OF METALS You should: Tick Examine the relationship between the method of extraction of a metal from its ore and its position in the reactivity series (e.g. aluminium, a reactive metal is extracted by electrolysis; iron, a less reactive metal, by chemical reduction) Use displacement and competition reactions of metals to determine their relative reactivity Explain the term reduction (removal of oxygen) and oxidation (gain of oxygen) and recognise their occurrence in reactions Know that the extraction of a metal requires the process of reduction Know the meaning of the terms electrolysis, electrode, anode, cathode and electrolyte Know the processes involved in the commercial extraction of aluminium , including being able to write and interpret word and balanced symbol equations for the reactions at the anode and the cathode Know the reasons for the high cost of the process and how these costs are minimised Know that recycling aluminium uses only about 5% of the energy needed to extract it from bauxite and saves waste Discuss the factors affecting the siting of an aluminium extraction plant Relate the uses of aluminium, copper and titanium to their properties Relate the uses of different steels to their composition and properties Know that steel is recycled on a large scale and that recycling steel saves 50% of the energy used in the extraction of iron, helps to conserve iron ore and also cuts down on the emission of greenhouse gases Evaluate the social, economic and environmental impact of the use and extraction of metals 2 Summary Sheet The reactivity series This booklet is all about metals. Some metals are more reactive than others. We can list them in order of their reactivity as follows; Displacement/competition reactions – often used to extract metals. A reactive metal can displace a less reactive metal from its compound. As an example, you saw a displacement reaction (the thermite reaction/Brainiac video) in core booklet 3. The thermite reaction is; Aluminium + iron oxide aluminium oxide + iron In this reaction aluminium is more reactive than iron. It therefore DISPLACES it from its oxide. It REDUCES the iron oxide. Extracting aluminium. metals from the ground; This is a picture of a gold mine (which looks much better in colour). Gold is an unreactive metal which means that it’s stable on its own. Because of this it is relatively easy to extract. 3 examples gold, iron and The more reactive a metal, the more stable are it’s compounds and therefore the more difficult they are to extract. Iron is a fairly reactive metal. It is found as an ore called haematite which is mainly iron oxide mixed with impurities. Iron is extracted in the Blast Furnace (Port Talbot Steelworks) using more reactive carbon to displace it. The carbon removes the oxygen from the iron. This is known as REDUCTION. Once extracted, the excess carbon is removed from the ‘pig’ iron forming steel. Steel is basically an alloy of iron and carbon although many other metals can be added to make many different types of steel. Here are some examples; Steel type Mild % Carbon < 0.5% Medium 0.5% – 1% High Carbon >1% Uses Bendable in thin sheets. Used for car bodies, food cans. Harder, used for hammer, axe heads Harder still but not as strong, used for scissors, knife blades, drill bits. Manganese steel is an alloy of iron (84%), manganese (15%) and carbon (1%). Manganese steel is extremely hard and is used for railroad switches and dredging equipment. Stainless steel is an alloy of iron (80%), chromium (15%), nickel (4%) and carbon (0.5 to 1%). Stainless steel is strong and hard, with a very high resistance to corrosion (due to chromium). It is used for cookware, cutlery and industrial chemical plant. Aluminium is a reactive metal. It is found as an ore called bauxite which is mainly aluminium oxide mixed with impurities. Aluminium is difficult to extract. The extraction process is known as electrolysis which is expensive and not particularly environmentally friendly. 4 Using electrolysis to reduce aluminium oxide and therefore produce aluminium. 1. the aluminium oxide has to be molten so that it splits into mobile ions Al3+ and O2-. This takes enormous amounts of energy. Aluminium oxide is an ionic compound. Because of its giant lattice structure it has a very high melting point (efforts to reduce the melting point of aluminium oxide are made by adding it to a substance called cryolite) 2. The molten aluminium oxide is now a liquid that can conduct electricity. It is known as an electrolyte. 3. The electrical current is switched on. 4. Al3+ ions attract to the negatively charged lining (the cathode electrode). At this point electrons moving out of the cathode are donated to the Al3+ ions so that aluminium atoms form. Voila! We have the aluminium. Al3+ + 3e Al 5. In the meantime the oxygen ions have attracted to the positively charged electrode (the anode). Here they have their excess electrons removed turning ions back into molecules. 2O2- - 4e O2 6. As oxygen forms at such high temperatures it actually reacts with the anode. The anode has to be replaced every so often. 5 Siting an aluminium extraction plant - site requirements include a source of cheap electricity, deep water facilities for the importation of raw materials and good road and rail communications. A site would also; require a large amount of open flat land, need to be near to a workforce but far away from local communities so that pollution issues were minimised. Environmental issues involved in the extraction of metals. The extraction of iron and aluminium are carried out at extremely high temperatures. Heat energy is created through the combustion of fossil fuels which as we know from core booklet 6a result in the formation of carbon dioxide. Carbon dioxide in turn contributes to global warming. Sulphur and nitrous oxides are also created during fossil fuel combustion these gases dissolve in water to form acid rain. In order to produce aluminium electricity is required. Creating electricity also involves the combustion of large amounts of fossil fuels which of course are non-renewable. Open cast mining to obtain metal ores results in scarring of landscapes and disruption to animal and plant habitats. Social and economic issues involved in the extraction of metals Take Port Talbot as an example. Port Talbot was an ideal site for the steelworks that remain there today because of its deep water port, access to coal (carbon) needed to reduce the iron oxide, open flat land and good transport links. Sandfields was built to house an influx of new workers and local businesses prospered. Port Talbot Steelworks attracted a great deal of investment into the area including the establishment of a chemical plant at Baglan by British Petroleum. Port Talbot Steelworks brought more money, more jobs and therefore more workers into the Port Talbot area as a result, more schools and more houses were built. Over the years as the chemical plant has shut down and steel production has decreased however, also because of pollution, economic prosperity has declined in the area and people have started to move away. The uses and properties of aluminium, copper and titanium. A property of a metal is how it behaves, for example it might be very strong, a good conductor of heat or electricity. Depending upon their properties, metals are used for different things, here are some examples. 6 Metal Titanium Use Hip replacement Property Non-toxic, extremely strong tennis rackets, golf Light, extremely clubs strong Metal sheathing Attractive colouring around buildings e.g. the Guggenheim museum in Bilbao in Spain. Copper Electrical cables Good conductor of electricity Copper pipes Resistant to corrosion, waterproof In cookware e.g. Attractive appearance, good conductor of heat. saucepans Aluminium Food wrapping Non-toxic, impermeable Aircraft Lightweight Mirrors Excellent reflective properties. Recycling metals such as iron and aluminium The disadvantages of extracting metal such as iron and aluminium are as follows: 1. Enormous amounts of energy are required resulting in the combustion of non-renewable fossil fuels. 2. During the combustion of fossil fuels large amounts of greenhouse gases are produced contributing to global warming. 3. CO2, NOX and SO2 produced during combustion cause acid rain. 4. Large areas of land are destroyed by open cast mining to obtain the ores. 5. Mining affects plant and animal habitats. One solution to these problems is to recycle rather than extract these metals. Recycling aluminium uses only about 5% of the energy needed to extract it from bauxite and saves waste. Steel is recycled on a large scale and which saves 50% of the energy used in its extraction. Recycling also helps to conserve iron and aluminium ore and also cuts down on the emission of greenhouse gases. END OF SUMMARY SHEETS 7 DISPLACEMENT/COMPETITION REACTIONS Metals are able to displace less reactive metals from their compounds in what are called DISPLACEMENT reactions, sometimes known as competition reactions. We can use displacement reactions to work out the reactivity series for metals. We can use the reactivity series of metals to PREDICT the outcome of a reaction. Class Prac – the displacement reactions of metals In this experiment you will be looking at the reactions between various metals and metal salt solutions. 8 Procedure 1. Take the plastic covered worksheet. 2. Place a copper turning in each box in the copper row. 3. Place one small piece of magnesium ribbon in each box in the magnesium row. 4. Place a few zinc granules in each box in the zinc row. 5. Place an iron nail in each box in the iron row. When all the pieces of metal are in place:7. Add two drops of copper sulphate to each metal in the first column. Observe and record your observations. 8. Add two drops of iron nitrate to each metal in the second column. Observe and record. 9. Add two drops of magnesium nitrate to each metal in the third column. Observe and record. 10. Finally, add two drops of zinc chloride to each metal in the fourth row. Observe and record. Results Copper sulphate solution Iron(III) nitrate solution Copper Magnesium Zinc Iron 9 Magnesium nitrate solution Zinc chloride solution Conclusion – using your results try to place your metals in order of reactivity. Increasing reactivity – put metals above arrow in correct order Write out equations for each reaction. simply write down no reaction. Copper + Copper sulphate Copper + Iron nitrate Copper + Magnesium nitrate Copper + Zinc chloride Magnesium + Copper sulphate Magnesium + Iron nitrate Magnesium + magnesium nitrate Magnesium + zinc chloride Zinc + Copper sulphate Zinc + Iron nitrate Zinc + Magnesium nitrate 10 If there was no reaction Zinc + Zinc chloride Iron + Copper sulphate Iron + Iron nitrate Iron + Magnesium nitrate Iron + Zinc chloride REDUCTION REACTIONS Most metals are found as metal oxides. To extract them the oxygen must be removed. A REDUCTION reaction is one in which oxygen is removed/lost. Watch the two teacher demos of reduction reactions. Write down word equations for both of them, N.B. both of these reactions can also be described as displacement reactions. Not only that, they are REDOX reactions because as the metal oxides are reduced the magnesium/carbon are gaining the oxygen; they are being oxidised. 1. Magnesium + Copper Oxide 2. Carbon + Lead Oxide Iron is removed from it’s oxide in the Blast Furnace by carbon in the same way as lead was removed in teacher demo 2. Write out a word equation for the reduction of iron oxide in the space below. Use equation 2 above to help you. This reaction is also how man discovered iron. + + 11 K.S communication Read page 4 and answer the following questions on the production of iron: 1. Iron is a fairly reactive metal. Which would be the easiest metal to extract; a reactive or an unreactive metal? __________________________________________________ 2. What is a reduction reaction? _____________________________________________ _____________________________________________ 3. What is steel? _____________________________________________ _____________________________________________ 4. Look at the table of mild, medium and high carbon steels. Write a sentence to describe the relationship between the % carbon and the hardness of steel. _____________________________________________ _____________________________________________ 5. Look at the bottom of page 7. What are the advantages of recycling steel? _____________________________________________ _____________________________________________ 6. Complete the table to show the composition, properties and uses of manganese and stainless steel. 12 The extraction of aluminium – another reduction reaction. 1. Look at the laminated cartoon cards showing the electrolysis of aluminium oxide. Put them into the correct order and draw them into the boxes below. 1 During this process aluminium oxide is heated to extreme temperatures so that its ions are free to move around. Al2O3(s) heat Al3+(l) + O2-(l) Molten aluminium oxide now acts as a liquid that conducts electricity – an electrolyte. 2 Electricity is passed through the molten electrolyte via positive and negative electrodes. As soon as the mobile ions are subjected to an electrical charge they run to their opposite electrodes 3 The positive aluminium ions are given their 3 valence electrons back by the cathode. They turn back into atoms. Al3+ + 3eAl(l) 4 The negative oxygen ions have their 2 valence electrons taken off them by the anode. They turn back into molecules. 2O2- - 4eO2(g) 5 Molten aluminium is tapped off from the bottom of the electrolysis cell and rolled into ingots for export elsewhere. 6 In the heat of electrolysis oxygen burns the carbon electrode forming carbon dioxide gas. The anodes thus have to be replaced from time to time. 13 2. Watch the short DVD of an aluminium extraction plant. Write known any notes on the ‘notepad’ below: 3. Electrolysis is also used to purify metals and to copper plate. Carry out a practical activity to copper plate a 1p coin. Stick your coin over the top of this one. Not in exam! 14 Debate - you are going to debate whether or not to site an aluminium extraction plant at Llandarcy, the site of the B.P oil refinery which closed there in 2000. In preparation for the debate write down a list of advantages and disadvantages that it would bring to the local area in the spaces below. Advantages Disadvantages 15 I.C.T – find and present. Copper, titanium and aluminium Using the internet find out about the history (local if possible), properties and uses of copper, titanium and aluminium. Add in any other little facts; for example, did you know that since the 1950’s there has been a titanium factory called TIMET in Waunarlwydd. During the cold war they used to make the titanium into parts to send nuclear bombs over to Russia. Now they use it for Rolls Royce engine parts. Relate the uses of these metals to their properties; for example you might say that aluminium is used in food wrapping because it’s non-toxic. If you complete your research you can go onto Birchfield Chemistry. Staple your research onto the back of this booklet. __________________________________ KEY WORDS FROM BOOKLET Extract to remove a metal from its ore Displacement Reaction one in which a reactive element removes a less reactive element from its compound. Reduction Reaction one in which oxygen is removed Reduce to remove oxygen Oxidation Reaction one in which oxygen is gained 16 Oxidise to supply oxygen REDOX reaction one in which oxidation and reduction occur at the same time Physical property how a substance behaves e.g it could be a good conductor of heat or electricity. Iron a fairly reactive metal element extracted in the Blast Furnace. Steel an alloy of mainly iron and carbon. Aluminium an abundant reactive metal with many useful properties extracted from its oxide by electrolysis. Electrolysis a process that separates a metal from a non-metal through the use of electricity Electrolyte a liquid that is able to conduct electricity Anode a positive electrode Anion a negative ion Cathode a negative electrode Cation a positive ion 17