Chemistry C1 3.2 - 3.6

3.5 Useful metals

Transition metals - in the centre block of the periodic table. Many have similar properties, like metals all the transition metals are good conductors of electricity and energy - they are strong, but can also be bent or hammered into useful shapes.

Properties, means that we can use these transition metals. Can be used in buildings, cars, trains, other transport. Use them in heating systems - electrical wiring - good conductors of electricity and energy.
Copper - transition metal - can be bent but is still hard enough to be used as water tanks or pipes. Doesn't react with water, copper conducts energy and electricity.
Ideal uses : pipes that will carry water, or wires that will conduct electricity.

Copper alloys - Bronze, first alloy, usually made by mixing copper with tin. Used to make ship propellers because it it tough and resistant to corrosion.
Make brass - alloying copper with zinc. Brass harder than copper - is still workable. Hammered and pressed - musical instruments.

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3.4 Continued

Extracting copper from low grade copper ores -
We now use bacteria ( bio leaching) and even plants (phytomining) to help extract low grade copper ores.
Phytomining - plants absorb copper ions from low grade copper ore as they grow - could be on **** heaps of previously discarded waste from processing copper- rich ores. The plants are then burnt and the metals can be extracted from the plants. The copper ions can be leached 'dissolved' from the ash by adding sulfuric acid solution. This makes copper sulfate - use displacement by scrap iron, and electrolysis to extract pure copper metal.

Bio leaching - bacteria feed on low grade metal ores, combination of biological and chemical processes, we can get a solution of copper ions called a 'leachate' from waste copper ore - once again we use scarp iron and and elactrolysis to extract the copper from the leachate.
20% of copper ore comes from bioleaching. Increase as copper supply runs out. Bioleaching is a slow process - scientists trying to find ways to speed it up ,at the moment it can take years to extract 50% of the metal from low grade ores.

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3.4 Continued

Metal ions - always positively charged - electrolysis attracted to negative electrode. Metals always deposited on the negative electrode.
In industry electrolysis carried out by a number of cells - method gives very pure copper needed to make electrical wiring.
Electrolysis also used - purify impure copper extracted by smelting. Industry, electrolysis cells use copper electrodes.

Copper extracted from copper sulfate solution in industry by adding scrap iron. Iron more reactive than copper - so can displace copper from solution.
Iron + copper sulfate ---> iron sulfate + copper

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3.5 continued

Aluminium alloys - low density metal, alloyed with a wide range of other elements. Alloys have very different properties - we can use some to build aircraft and others can be used as military amour on tanks/ other military vehicles.

Gold alloys - we can make gold harder by adding other elements. Usually we alloy gold with copper when we use it in jewellery. Pure gold wears away more easily than its alloys with copper. Varying the proportions of the two metals - different shades of 'gold' objects.

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3.6 Metallic issues

Exploiting metal ores - whenever we mine ores from the Earth's crust = environmental consequences. Open cast mining often used to get copper ore from the ground, ores of aluminium and iron are also mined like this. Huge pits, scar the landscape, noise and dust pollution, destroying habitats of animals and plants.

Water in the area can also be affected, rain drains through exposed ores, and **** heaps of waste, groundwater = very acidic.
Ores must be processed, to extract the metals, sulfide ores are heated strongly in smelting - sulfur dioxide escapes causing acid rain.

Recycling Metals - a lot of aluminium is used, it is important to recycle it, apsves energy and money as it doesn't involve electrolysis - 95% energy saving (recycling to mining). We also recycle iron and and steel 'tin cans' are coated with a thin layer of tin to prevent rusting. Cans can be separated as are metallic (from rubbish)
Recycled can steels save about 50% of the energy used to extract iron and turn it into steel. Most energy used by burning fossil fuels - recycling helps maintain supplys.

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Gold Continued

Because gold is so unreactive, it is found as the native metal and not as a compund ---->  not needed to be chemically seperated. However chemical reactions, may need to remove contraminated metals.

We only extract a metal, if it is economically worthwhile and how easy it is to extract from its ore. (how much metal the ore contains) - whether its worth extracting = - How easy it is to extract from the ore

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3.6 Continued

Benefits of using metals in construction -
Copper is a good electrical conductor for wiring; it is not reactive so can be made into water pipes.
Lead can be bent easily so is used to seal joints on roofs.
Steel is strong for girders and scaffolding.
Aluminium alloys are corrosion - resistant.
Drawbacks -
Iron and steel can rust, severely weakening structures e.g. If the iron rods used inside reinforced concrete rust, structures can collapse.
The exploitation of metal ores to extract metals causes pollution and uses up the Earth's limited resources.
Metals are more expensive than other materials such as concrete.

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3.6 Continued

Copper also recycled - tricky as often alloyed with other metals. So it would need to be purified for use as electrical wiring. Recycling metals reduces the need to mine for ores and conserves the Earth's resources. It also prevents any pollution problems that arise from extracting metal from its ore.

Metallic structures - steel most commonly used metal. Often used in construction injury = where strength is needed. Sky scrapers have steel girders to support them, suspension bridges use thick steel cables, concrete bridges over motorways are made from concrete - reinforced with steel rods.

Steel - some drawbacks - iron in it tends to rust - stainless steel could be used but only for small jobs, more expensive than ordinary steel. Even so, protecting the steel from rusting also costs money. Coatings - paint or grease - reapplied regularly - rusting will affect the strength of the steel and can be dangerous

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C1 3.4 Extracting Copper

Extract most copper from copper rich ores - limited and are running out.

Two main methods of removing copper from ore :
In one method we use sulphuric acid to produce copper sulfate solution, before extracting copper.
In another process, known as smelting, we heat copper ore very strongly in a furnace with air to produce crude copper.
E.g. Copper can be found in an ore called chalcocite - contains copper sulphide, Cu2S, if we heat the copper sulphide in air, it decomposes to give copper metal.
Copper sulphide + oxygen ---> copper + sulfur dioxide

Care taken to avoid letting sulfur dioxide gas into the air - chimneys fitted with basic 'scrubbers' to neutralise acidic gases.
Then we use impure copper - as positive electrode - in electrolysis to make pure copper. 80% of copper produced by smelting.
Smelting + purifying copper ore = lots of heat and energy (costs and impacts on environment).

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3.3 Continued

Before the displacement of of titanium can take place, the titanium ore must be processed. This involves seperating titanium oxide fromand converting it into chloride. Then the chloride is distilled and purified. Only then is it ready for titanium to be dispalced by the sodium or magnesium - each step takes time and costs money.

Image result for a hip replacement

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Extracting Metals 3.1

Method of extraction of a metal from its ore depends on the stability of its compound, in the ore. (Which depends on the reactivity of the metal).

Metal oxide + carbon ----> metal + carbon dioxide

Oxides of very reactive metals,e.g. aluminium, form stable oxides and other compounds. A lot of energy is needed to reduce them to extract the ore.

The oxides of less reactive metals, e.g. iron, form less stable oxides and other compunds  - relatively little energy is needed to reduce them, to extract the metal. 

Method of extraction - of a metal depends from ore - reactivity series.

Potassium, Sodium, Calcium, Magnesium and aluminium = Electrolysis

Carbon = a non metal (and Hydrogen 11th)

Zinc, iron, tin and lead = reduction by carbon or carbon monoxide.

Copper, silver, gold and platinum = Various chemical reactions (Blue - Found as native state)

Because gold is so unreactive, it is found as the native metal and not as a compund ---->  not needed to be chemically seperated. However chemical reactions, may need to remove contraminated metals.

We only extract a metal, if it is economically worthwhile and how easy it is to extract from its ore. (how much metal the ore contains) - whether its worth extracting = - How easy it is to extract from the ore

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3.2 Irons and Steels

Iron straight from the blast furnace has limited uses - it is brittle, although very hard, can't be easily compressed. When molten = it can be poured into moulds e.g. to make wood burning stoves.

We can treat the iron from the blast furnace to remove the main impurit carbon (96% Iron, and 4% Impurities) Removing all the carbon and other impurities from cast iron gives us pure iron. This is very soft and easily shaped - however too soft for most uses - to make it more useful, we have to add tiny amounts of other metals, such as cronium and nickle.

We call a metal that is mixed with other elements is called an alloy. Steel is an alloy of iron. By adding elements in carefully controlled amounts, we can change the properties of the steel.

Steel is not a single substance, like alloys it is a mixture. All of them are are alloys of iron with carbon/ and or other elements.

The simplest steelas are carbon steels - made by removing most carbon from cast iron - leaving small amounts of carbon (0.03% to 1.5%).

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3.2 continued

Cheapest steels to make - products such as body work of cars, knives and machinery.

Often carbon steels contain other elements aswell. High carbon steel - is very strong but brittle. Low cabon steel is soft and easily shaped. It is not as strong - much less likely to shatter on impact with a hard object.

Mild steel - low carbon steel - less than 0.1% carbon. Is easily pressed into shape - mass production e.g car bodies.

Alloy steels =

Low-alloy steels are more expensive than carbon - steels because they contain between 1% and 5% of other metals. Even more expensive than high alloy steels - contain a higher percentage of other metals (chronium - nickel steels are known as stainless steels - cooking and cutlery due to the fact that they are hard and strong and have a great resistance to corrosion - they don't rust.  

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Extracting metals and Iron and steels 3.1 and 3.2

Because gold is so unreactive, it is found as the native metal and not as a compund ---->  not needed to be chemically seperated. However chemical reactions, may need to remove contraminated metals.

We only extract a metal, if it is economically worthwhile and how easy it is to extract from its ore. (how much metal the ore contains) - whether its worth extracting = - How easy it is to extract from the ore.

Native ---> Unreactive (can be picked up e.g. Gold)

An ore ---> is a rock containing enough metal to make it economically worth extracting.

Oxidation - adding oxygen to a chemical compound.

Reduction - The removal of oxygen from a chemical compund.

Iron from a blast furnace is called cast iron or pigiron. Pure iron has a regular arrangement of atoms with layers.

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3.3 Aluminium and Titanium

Although very strong, metals can also be very dense. We have to use metals that are both strong and are low - density (strong and light). Aluminium and titanium are often chosen = these metals are light and strong and also do not corrode.

Aluminium, silvery and shiny, very light - excellent conductor of electricity and energy, we can also shape it and draw it into wires very easily. Aluminium is a relatively reactive metal - doesnt't corrode very easily - this is because the aluminium metals at the surface react with the oxygen in air. Form a thin layer of aluminium oxide - layer stops any futher corrosion taking place.

Aluminium is not a particualry strong metal - can use it to form alloys. Alloys are harder, more rigid and stronger than pure aluminuim. Uses of aluminium: Drinks cans, cooking foil, saucepans and high voltage power cables.

Extracting aluminium --->

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3.3 Continued

Properties and uses of titanium ---> Titanium is a silvery, white metal - it is strong and very resistant to corrosion. Oxide layer protects it (aluminium)
Although it is denser than aluminium, it is less danse than most other metals. Titanium - a very high melting point - about 1660 degress - uses at very high temperatures.

Uses --> bodeis of high-performace aircarft and racing bike - strong and light, parts of jet engines - can withstand high temps - nuclear reactors - temp and resistance to corrosion, relpacement hip joints - resitant to corrosion, strength and low density. 

Extracting Titanium --> Not particuarly reactive, produce by displacing it form its oxide using carbon - unfortunately carbon reacts with titanium = making it very brittle. Have to use a more recative metal than carbon. We use sodium or magnesium. However both have to be extracted by electrolysis themselves in the first place. 

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3.3 Continued

Extracting aluminium --->

Aluminium is a reactive metal, we cannot use carbon to dispalce it form its oxide - instead we extrcat using electrolysis. An electric current is passed through molten aluminium oxide at a high temperatures to break it down.

Mine aluminium ore -  contains aluminium oxide and impurities - it is then seperated from the impurities, the oxide must be melted before electrolysis can take place.

Problems with electrolysis = is that it's very expensive - due to expensive process ( have to heat to a very high temperatur and needing a great deal of energy in order to extract metal from its molten compound). Also environmental issues to consider when using high amounts of energy.

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A blast furnace

Related image (http://www.bbc.co.uk/staticarchive/78e0f5f20d5d72a2b5d27c083ee714d1ec75bec3.jpg)

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