Topic 3: Metals and Metal Extraction (3 weeks)

Key Idea 3: The Activity/Reactivity Series of Metals is a list of some of the most common metals in order from most to least reactive. Conduct displacement reactions in order to determine the order of metals in the Reactivity Series. Predict whether a metal is likely to occur in nature either as an element or a compound, given its relative position in the Reactivity Series.

Metal Reactivity Series and Minerals Reactivity of metals is based on how readily they lose their electrons. The least reactive metals can be found in element form (copper and below). Those above copper are nearly always found in compounds.

An Activity Series can be used to predict the outcome of a reaction The position of a metal on the activity series can be used to predict the outcome of a Metal Displacement (or Single Displacement) reaction. Cu(s) + 2AgNO3 (aq) Cu(NO3)2 (aq) + 2Ag(s) Copper + silver nitrate copper nitrate + silver Copper is higher than silver in the Reactivity Series. Copper can displace silver from it silver compounds (e.g. silver nitrate).

The method used to extract a metal from its ore depends on the reactivity of the metal. K Na Ca Mg Al Zn Fe Sn Pb Cu Ag Au Pt Most reactive Very reactive metals – extracted using electrolysis C More reactive metals – usually extracted by reduction – heating with carbon to remove oxygen H Unreactive metals – little or no extraction needed Least reactive Sometimes non-metals are included for reference.

Metals and Alloys An alloy is a mixture of a metal with at least one other element. Steel is a common example of an alloy. It contains iron mixed with carbon and other elements. Adding other elements to a metal changes its structure and so changes its properties. The final alloy may have very different properties to the original metal. By changing the amount of each element in an alloy, material scientists can custom-make alloys to fit a given job.

Metals and Alloys Alloys have been used for thousands of years. Bronze, an alloy of copper and tin, was commonly used by civilizations before iron extraction methods were developed. Other well-known alloys include: brass: an alloy of copper and zinc. It does not tarnish and is used for door knobs, buttons and musical instruments.

Properties and uses of alloys solder: an alloy of zinc and lead. It is used in electronics to attach components to circuit boards. amalgam: an alloy of mercury and silver or tin. It is used for dental fillings because it can be shaped when warm and resists corrosion. Why alloys? Increase the hardness and strength of metals Prevent corrosion or rusting And simply- it looks better!

Why is steel stronger than iron? The atoms in pure iron are arranged in densely-packed layers which can slide over each other. This makes pure iron a very soft material. The atoms of other elements are different sizes. When other elements are added to iron, their atoms distort the regular structure of the iron atoms. It is more difficult for the layers of iron atoms in steel to slide over each other and so this alloy is stronger than pure iron. Draw a diagram for pure iron and a diagram for steel (an alloy). Explain why alloys are used, what is the benefit of mixing the metal with other elements?

Types of Steel Steel can contain up to 2% carbon. Varying the amount of carbon gives steel different properties. For example, a higher carbon content makes a hard steel. Different types of steel are classified by how much carbon they contain. low carbon steel contains less than 0.25% carbon high carbon steel contains more than 0.5% carbon. Two other important types of steel are: stainless steel – an alloy of iron that contains at least 11% chromium and smaller amounts of nickel and carbon titanium steel – an alloy of iron and titanium.

GOLD What are the grades of gold we can get? Why are they different? What are the different colours of gold? What gives the gold it’s colour?

Gold Alloy 24, 22, 18, 14, 9 carat 24 carat gold in jewellery form would be too soft, so jewellery is not made from 100% gold. So what do we to make it harder? Gold is always referred to in terms of 24ths 24 carat gold is pure gold = 24/24 99.9% gold 18 carat = 75% gold and 25% other metal/metals

White gold is a mixture of silver and gold The colour of the gold will depend on the percentages of copper or silver added to the gold. White gold is a mixture of silver and gold Rose gold is a mixture of copper and gold The more copper added to the gold, the redder it will get The more silver added to the gold the whiter it will get

Key Idea 4: The method of metal extraction from its mineral is determined by the metal’s reactivity. Compare the methods (including cost) for extracting aluminium and iron based on their relative reactivities.

The reactivity of a metal determines how it is extracted 1. Silver (Ag) and gold (Au) need no extraction because they exist as element in nature. 2. Copper and mercury can be extracted from their ore by burning directly in air 3. Metals which are less reactive than carbon in reactivity series are extracted from their ore by displacement reaction using carbon or aqueous electrolysis. 4. Those metals which are more reactive than carbon are extracted by molten electrolysis

The reactivity of a metal determines how it is extracted Silver (Ag) and gold (Au) need no extraction because they exist as elements in nature. Gold, because it is so unreactive, is found as the native metal and not as a compound. It does not need to be chemically extracted from its ore, but chemical reactions may be needed to remove other elements that might contaminate the metal.

The reactivity of a metal determines how it is extracted 2. Copper and mercury can be extracted from their ore by burning directly in air – ‘roasting’ Physical Processes Mining → Crushing → Grinding → Concentrating → Chemical Processes Roasting → Smelting → Conversion → Refining Roasting: reduces impurities in the copper ore and produces calcine (a mixture of products)

The reactivity of a metal determines how it is extracted 3. Metals which are less reactive than carbon in reactivity series are extracted from their ore by displacement reaction using carbon or carbon monoxide or aqueous electrolysis. Detailed example: Iron (obtained from haematite) Understand and write equations for the processes that occur in a blast furnace. Describe the Basic Oxygen Steelmaking (BOS) Process.

Key Idea 5: Iron (obtained from haematite) is alloyed with various substances to produce different types of steel, which have a wide variety of uses. Understand and write equations for the processes that occur in a blast furnace. Describe the Basic Oxygen Steelmaking (BOS) Process.

The extraction of iron from ore- an overview Australia has some of the largest iron ore deposits and is one of the largest iron-ore producers. Iron is the second most abundant metal in the Earth’s crust. Almost all iron ore is used in blast furnaces to make pig iron which is the main material in steelmaking. Iron can be alloyed with a variety of elements to produce materials useful in the construction and manufacturing industry. https://www.youtube.com/watch?v=i6BIyQJZdTg

The extraction of iron from ore Examples of common iron ores Haematite (Fe2O3) Magnetite (Fe3O2) Pyrite (FeS2) Iron ore is reduced via a chemical reduction reaction with carbon (coke) in a blast furnace. (iron from haematite (Fe2O3))

The extraction of iron from ore Raw materials Iron ore (hematite) mainly (Fe2CO3) Calcium carbonate (CaCO3) Coke (C) Coke is coal heated in the absence of air - 85-90% carbon

Iron is produced in a blast furnace Step 1 Oxidation of carbon C + O2  CO2 Hot air into blast furnace Coke burns in the limited air Heats furnace Forms carbon dioxide gas

Iron is produced in a blast furnace Step 1 reduction of carbon dioxide CO2 + C  2CO Carbon dioxide reacts with coke Carbon monoxide gas formed

Iron is produced in a blast furnace Step 2 Fe2O3 + 3CO  2Fe + 3CO2 Carbon monoxide reacts with iron oxide Reducing it to molten iron and carbon dioxide Flows to bottom of furnace reduction of iron ore with carbon monoxide

Roles of Limestone The main impurities in the ore are silicon dioxide SiO2 and aluminium oxide Al2O3 The limestone (CaCO3) combines with the silica and alumina to produce slag which floats on top of the molten iron. The limestone also gives off CO2. Decomposition of limestone CaCO3 CaO + CO2 CaO + SiO2 CaSiO3 calcium silicate Al2O3 + CaO Ca(AlO2) 2 calcium aluminate

Pig Iron The product of the blast furnace extraction is Pig iron which contains 4-5% carbon, as a result of the refining process. It is Brittle, and Hard. There is a need to refine it further to remove carbon.

Reactions Summary Step 1: Step 2: a) The oxidation of carbon Carbon (coke) reacts with oxygen to form carbon dioxide. C + O2  CO2 b) The reduction of carbon dioxide Carbon dioxide reacts with carbon (coke) to form carbon monoxide (a stronger reducing agent that carbon dioxide) C + CO2  2CO Step 2: a) The reduction of Iron ore with carbon monoxide Iron oxide reacts with carbon monoxide to form molten iron and carbon dioxide. Fe2O3 + 3CO  2Fe + 3CO2

PREVENTS iron from being oxidised Why limestone? Step 3: a) The decomposition of limestone Calcium carbonate decomposes with heat to form calcium oxide and carbon dioxide. CaCO3  CaO + CO2 b) Formation of ‘slag’ (Calcium Silicate) Calcium oxide reacts with silicon dioxide (from ore) to form calcium silicate. CaO + SiO2  CaSiO3 PREVENTS iron from being oxidised

The Blast Furnace - Summary Metals that are less reactive than carbon can be extracted from their ores by burning with carbon. Iron is extracted by this method in a blast furnace. The iron ore is heated with carbon-rich coke at very high temperatures. The iron collected from a blast furnace is only 96% pure, called ‘pig iron’. Usually, this product will be treated further because the impurities make iron brittle. raw materials hot air molten iron molten slag

http://www.bbc.co.uk/history/british/victorians/launch_ani_blast_furnace.shtml

Iron is alloyed with various substances to produce different types of steel Plain carbon steels Alloy steels Stainless steels Cast irons

Which contains highest % of iron?? PIG IRON: semi-finished metal produced from iron ore in blast furnace, containing 92% iron high amounts of carbon (typically up to 3.5 percent), and balance largely manganese and silicone plus small amounts of phosphorus, sulfur, and other impurities. Pig iron is further refined in a furnace for conversion into steel. STEEL is an alloy of iron and carbon. The amount of carbon dictates whether a steel is hard or it is tough. Adding Carbon makes the iron harder. The more carbon the harder the steel. Carbon content in steel  usually falls a range between 0.3 ~ 1.5 %  by volume. STAINLESS STEEL is a common name for metal alloys that consist of 10.5% or more Chromium (Cr) and more than 50% Iron (Fe). Although it is called "stainless", a better term for it is "highly stain resistant". A somewhat dark metal, it looks bright because it reflects light.

Low-carbon steels Medium-carbon steels High carbon steels Iron ALLOY that contain less than 0.25%C Not very responsive to heat treatments soft, weak, tough and ductile Machinable, weldable, not expensive Medium-carbon steels Contain 0.25-0.60 wt.% carbon Can be heat-treated but only in thin sections Stronger than low-C steels but less ductile and less tough Good wear resistance Railway wheels & tracks, gears High carbon steels 0.60 -1.4 wt.% C Hardest, strongest, least ductile of all steels Almost always used in tempered condition. Especially wear resistant Used in cutting tools, dies, knives, razors, springs and high strength wires

Stainless steels Alloy of IRON Highly resistant to corrosion in many environments Predominant alloying element is at least 11% Chromium Corrosion resistance may be enhanced by Ni and Mo additions Used at high temperatures (up to ~ 1000 C) and severe environments Gas turbines, steam boilers, aircraft, missiles

Cast irons Theoretically contains > 2.14 % carbon Usually contains between 3.0 - 4.5% Carbon, hence very brittle Also 1 - 3 % silicon Since they become liquid easily between 1150˚C and 1300˚C, they can be easily cast Inexpensive Machinable, wear resistant 4 types: gray cast iron, nodular cast iron, white cast iron, malleable cast iron

Basic Oxygen Steelmaking (BOS) Process The process involves reacting oxygen with molten pig iron to lower the carbon content. “BASIC” The refractory lining (CaO and MgO) lines the ladles to withstand the high temperatures of molten metal. “OXYGEN” Nearly pure oxygen is blown through a lance to remove carbon and other impurities. The main impurities are: Carbon Sulphur Phosphorus Silicon

Basic Oxygen Steelmaking (BOS) Process C + O2  CO2(g) 4P + 5O2  P4O10 {P4O10 + 6CaO 2Ca3(PO4)2} Si + O2  SiO2 {SiO2 + CaO  CaSiO3} S + O2  SO2(g) With the exception of the carbon monoxide, the products react with lime, added during the oxygen blow to form a slag.

Basic Oxygen Steelmaking (BOS) Process The Basic Oxygen Steelmaking (BOS) Process.   The process uses modern furnaces lined with special bricks containing 90% magnesium oxide and 10% carbon. These can take up to 350 tonnes of reactants and convert them to steel in less than 40 minutes. http://www.tatasteelconstruction.com/en/reference/teaching-resources/building-in-steel/making-steel/from-iron-to-steel/basic-oxygen-steelmaking

Basic Oxygen Steelmaking (BOS) Process The furnace (aka. converter or vessel) is charged with steel scrap (up to about 30%) and molten iron from a ladle. An oxygen lance, cooled by circulating water, is lowered into the furnace and high purity oxygen is injected into the vessel at twice the speed of sound which ensures that all the impurities are converted into their oxides.

The blast furnace http://www.youtube.com/watch?v=Ea_7Rnd8BTM&feature=related http://www.bbc.co.uk/history/interactive/animations/blast_furnace/index_embed.shtml http://www.youtube.com/watch?v=uSgk73-W0kY&feature=related

Reduction of a metal oxide practical Aim: To obtain a metal from a metal oxide.   Method Place a spatula full of copper (II) oxide powder into a crucible. Add two spatulas full of powdered charcoal (carbon) and mix the two substances. Add a little more charcoal to the top of the mixture. Heat the crucible strongly over a Bunsen burner flame for a few minutes. Then allow to cool. Use tongs to tip the contents of the crucible onto a tile or piece of paper. Examine the contents to see if any orange-brown copper metal is present.

Displacement Reactions Single displacement reactions A displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Both metals and non-metals take part in displacement reactions.

An Activity Series can be used to predict the outcome of a reaction The position of a metal on the activity series can be used to predict the outcome of a Metal Displacement (or Single Displacement) reaction. Cu(s) + 2AgNO3 (aq) Cu(NO3)2 (aq) + 2Ag(s) Copper + silver nitrate copper nitrate + silver Copper is higher than silver in the Reactivity Series. Copper can displace silver from it silver compounds (e.g. silver nitrate).

Roles of Limestone The main impurities in the ore are silicon dioxide SiO2 and aluminium oxide Al2O3 The limestone (CaCO3) combines with the silica and alumina to produce slag which floats on top of the molten iron. The limestone also gives off CO2. Decomposition of limestone CaCO3 CaO + CO2 CaO + SiO2 CaSiO3 calcium silicate Al2O3 + CaO Ca(AlO2) 2 calcium aluminate

But where do the impurities come from? Hematite (ore) is washed in a current of water to remove impurities (dirt, clay, organic material etc) After this rinsing step the ore may still contain silicon dioxide and aluminium oxide as an impurity!

https://www.youtube.com/watch?v=KmhD8BmEFIo An experiment to determine which is more reactive: copper or iron You are given: iron filings, copper foil, copper sulfate solution, iron sulfate solution and a few test tubes

Key Idea 3: The Activity/Reactivity Series of Metals is a list of some of the most common metals in order from most to least reactive. Conduct displacement reactions in order to determine the order of metals in the Reactivity Series. Predict whether a metal is likely to occur in nature either as an element or a compound, given its relative position in the Reactivity Series.

Complete the following a) Zn (s) + Cu(NO3)2 (aq)  zinc + copper nitrate  b) Ca (s) + 2H2O (l)  calcium + water  c) Mg (s) + AgNO3 (aq)  magnesium + silver nitrate  d) Cu (s) + H2SO4(aq)  copper + sulphuric acid 

Complete the following a) Zn (s) + Cu(NO3)2 (aq)  zinc + copper nitrate  b) Ca (s) + 2H2O (l)  calcium + water  c) Mg (s) + AgNO3 (aq)  magnesium + silver nitrate  d) Cu (s) + H2SO4(aq)  copper + sulphuric acid  Zn(NO3)2 (aq) + Cu (s) zinc nitrate + copper Ca(OH)2 (aq) + H2(g ) calcium hydroxide + hydrogen Mg(NO3)2 (aq) + Ag(s) Magnesium nitrate + silver No reaction

DISPLACEMENT prac We looked at some metal displacement reactions so that we could form our own metal reactivity series The iron reaction with silver We didn’t see much of a change to our iron nails (while we should have seen that the iron solid displaced silver out of the solution) We should have rubbed down the nail with some steel wool first to remove an oxide layer. (ALLOYS ARE LESS REACTIVE THAN PURE METAL)

Results obtained: Mg2+ Cu2+ Pb2+ Ag+ Zn2+ Fe2+ Mg Copper metal Lead metal Silver metal Zinc metal Iron metal Cu No reaction Pb Ag Zn Fe

Reactivity series (as expected?) Magnesium (displaced all other metals) Zinc Iron Lead Copper Silver (we didn’t have silver solid but it was displaced by all other metals)

Practise reactions Mg (s) + CuSO4 (aq) Cu (s) + 2AgNO3 (aq) Cu (s) + Zn(CH3COO)2 (aq) Fe(s) + Pb(NO3)2 (aq) Zn(s) + Fe(NO3)2 (aq) Pb (s) + MgCl2 (aq)

Answers MgSO4 (aq) + Cu(s) 2Ag(s) + Cu(NO3)2 (aq) No reaction Fe(NO3)2 (aq) + Pb(s) Zn(NO3)2 + Fe(s)

What to condiser in The large scale manufacture of chemicals and MINing Raw materials: material that came from nature and are in an unprocessed or minimally processed state. Iron ore, logs, and crude oil, would be examples. Waste Product: results of reactions and/or processes in the industrial plant. Some may be toxic or harmful to environmental ecosystems so adequate waste measures required.   By-products: A by-product is a secondary or incidental product deriving from a manufacturing process, a chemical reaction or a biochemical pathway, and is not the primary product or service being produced. A by-product can be useful and marketable, or it can be considered waste. Energy costs: Economics The economic viability of a chemical plant can be improved by reducing energy costs and transport costs and by improving the efficiency of the process (ie: by the use of different catalysts or by changing reaction conditions). Yield: the amount of useful material made compared with maximum possible Safety: careful management and construction so as to avoid injury to all workers.