Edexcel IGCSE Chemistry Extraction & Uses of Metals PDF

Head to www.savemyexams.com for more awesome resources Edexcel IGCSE Chemistry Your notes Extraction & Uses of Metals Contents Sources of Metals Extracting Metals Using Metals Alloys...

Head to www.savemyexams.com for more awesome resources Edexcel IGCSE Chemistry Your notes Extraction & Uses of Metals Contents Sources of Metals Extracting Metals Using Metals Alloys Page 1 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Sources of Metals Your notes Sources of metals The Earth’s crust contains metals and metal compounds such as gold, copper, iron oxide and aluminium oxide Useful metals are often chemically combined with other substances forming ores A metal ore is a rock that contains enough of the metal to make it worthwhile extracting They have to be extracted from their ores through processes such as electrolysis, using a blast furnace or by reacting with more reactive material In many cases the ore is an oxide of the metal, therefore the extraction of these metals is a reduction process since oxygen is being removed Common examples of oxide ores are iron and aluminium ores which are called haematite and bauxite respectively Unreactive metals do not have to be extracted chemically as they are often found as the uncombined element This occurs as they do not easily react with other substances due to their chemical stability Examples include gold and platinum which can both be mined directly from the Earth’s crust Examiner Tips and Tricks A metal can reduce another metal (remove oxygen) only if it is more reactive than the metal that is bonded to the oxygen. Page 2 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Extracting Metals Your notes Extracting Metals Extraction of metals and the reactivity series The most reactive metals are at the top of the series The tendency to become oxidised is thus linked to how reactive a metal is and therefore its position on the reactivity series Metals higher up are therefore less resistant to oxidation than the metals placed lower down which are more resistant to oxidation The position of the metal on the reactivity series determines the method of extraction Metals extraction method table Metal Extraction method Most reactive Potassium Extracted by electrolysis of the molten chloride or oxide Large amounts of electricity are required, which makes this an expensive process Sodium Lithium Calcium Magnesium Aluminium Zinc Extracted by heating with a reducing agent such as carbon or carbon monoxide in a blast furnace Iron A cheap process as carbon is cheap and can also be a source of heat Copper Page 3 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Silver Found as pure elements Your notes Gold Least reactive The extraction method depends on the position of a metal in the reactivity series Higher placed metals (above carbon) have to be extracted using electrolysis as they are too reactive and cannot be reduced by carbon Lower placed metals can be extracted by heating with carbon which reduces them The extraction method depends on the position of a metal in the reactivity series Extraction of Iron from Hematite Iron is extracted in a large container called a blast furnace from its ore, hematite Modern blast furnaces produce approximately 10,000 tonnes of iron per day This is a continuous process with new raw materials added and products removed all the time due to the time and cost associated with getting the furnace up to temperature The Blast Furnace Page 4 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Page 5 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources There are three main zones in the blast furnace The raw materials: iron ore (hematite), coke (an impure form of carbon), and limestone are added into Your notes the top of the blast furnace Hot air is blown into the bottom Table of raw materials and their uses Raw material Formula Use Iron ore (hematite) Fe2O3 Source of iron Coke C To provide carbon Limestone CaCO3 To neutralise acidic impurities Zone 1 Coke burns in the hot air forming carbon dioxide The reaction is exothermic so it gives off heat, heating the furnace carbon + oxygen → carbon dioxide C (s) + O2 (g) → CO2 (g) Zone 2 At the high temperatures in the furnace, more coke reacts with carbon dioxide forming carbon monoxide Carbon dioxide has been reduced to carbon monoxide carbon + carbon dioxide → carbon monoxide CO2 (g) + C (s) → 2CO (g) Zone 3 Carbon monoxide reduces the iron(III) oxide in the iron ore to form iron This will melt and collect at the bottom of the furnace, where it is tapped off: iron(III) oxide + carbon monoxide → iron + carbon dioxide Fe2O3 (s) + 3CO (g) → 2Fe (I) + 3CO2 (g) Page 6 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Removal of impurities Limestone (calcium carbonate) is added to the furnace to remove acidic impurities in the ore Your notes The calcium carbonate in the limestone thermally decomposes to form calcium oxide calcium carbonate → calcium oxide + carbon dioxide CaCO3 (s) → CaO (s) + CO2 (g) The calcium oxide formed reacts with the silicon dioxide, which is an impurity in the iron ore, to form calcium silicate by neutralisation calcium oxide + silicon dioxide → calcium silicate CaO (s) + SiO2 (s) → CaSiO3 (l) This melts and collects as a molten slag floating on top of the molten iron, which is tapped off separately Extraction of Aluminium Aluminium is a reactive metal, above carbon in the reactivity series Its main ore, is bauxite, which contains aluminium oxide Aluminium is higher in the reactivity series than carbon, so it cannot be extracted by reduction using carbon Instead, aluminium is extracted by electrolysis The electrolytic cell for extraction of aluminium Page 7 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Diagram showing the extraction of aluminium by electrolysis Bauxite is first purified to produce aluminium oxide, Al2O3 Aluminium oxide is then dissolved in molten cryolite This is because aluminium oxide has a melting point of over 2000°C which would use a lot of energy and be very expensive The resulting mixture has a lower melting point without interfering with the reaction The mixture is placed in an electrolysis cell, made from steel, lined with graphite The graphite lining acts as the negative electrode, with several large graphite blocks as the positive electrodes At the cathode (negative electrode): Aluminium ions gain electrons (reduction) Molten aluminium forms at the bottom of the cell The molten aluminium is siphoned off from time to time and fresh aluminium oxide is added to the cell Al3+ + 3e– → Al Page 8 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources At the anode (positive electrode): Oxide ions lose electrons (oxidation) Your notes Oxygen is produced at the anode: 2O2– → O2 + 4e– The carbon in the graphite anodes reacts with the oxygen produced to produce CO2 C (s) + O2 (g) → CO2 (g) As a result the anode wears away and has to be replaced regularly A lot of electricity is required for this process of extraction, this is a major expense Examiner Tips and Tricks Make sure you can explain why aluminium is extracted by electrolysis while iron is extracted by reduction as it is a question that often comes up. Page 9 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Using Metals Your notes Uses of metals The uses of aluminium, copper and steel are summarised in these tables: Uses of Aluminium Use Property Aircraft bodies High strength-to-weight ratio (low density) Saucepans Very good conductor of heat and unreactive Overhead electrical cables Very good conductor of electricity Food cans Non-toxic, resistant to corrosion and resistant to acidic food stuffs Uses of copper Use Property Electrical wiring Very good conductor of electricity and ductile Saucepans Very good conductor of heat, unreactive, malleable Water pipes Unreactive (does not react with water), non-toxic and malleable Uses of iron Use Property Building material Good strength, malleable and ductile, relatively inexpensive Catalyst Variable oxidation state* Increases the rate of reaction without being used up Page 10 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources * This is beyond the scope of this specification but included for completeness Uses of Steel Your notes Type of Iron alloyed with Use Property steel Mild 0.25% C Car body panels and wiring Soft and malleable High carbon 0.5-1.4% C Tools, e.g. chisels Hard Stainless 20% Cr and 10% Cutlery, sinks and chemical Strong and resistant to Ni plants corrosion Page 11 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Alloys Your notes Alloys An alloy is a mixture of two or more metals or metal with a non-metal such as carbon Steel is made from iron and carbon Alloys often have properties that can be very different from the metals they contain They can be stronger and harder They are resistance to corrosion or extreme temperatures These enhanced properties can make alloys more useful than pure metals Alloys are harder than pure metals because: Alloys contain atoms of different sizes This distorts the regular arrangements of atoms So it is more difficult for the layers of atoms to slide over each other Brass is a common example of an alloy which contains 70% copper and 30% zinc Alloy structure Page 12 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes The regular arrangement of a metal lattice structure is distorted in alloys Examiner Tips and Tricks Questions on this topic often give you a selection of particle diagrams and ask you to choose the one which represents an alloy. It will be the diagram with uneven sized particles and distorted layers or rows of particles. Page 13 of 13 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers