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Extracting Metals
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- 1Extracting MetalsChemistry 1a 2.1 - 2.7
- 2Where are metal ores found?In the Earth's crust, we often find them combined with other chemical elements such as oxygen. This means that the metal must be separated before it can be used.
- 3What is extracting a metal dependent on?1) How easy it is to extract from the ore.
2) How much metal the ore contains. - 4What is a metal ore?Where there is enough of a metal or metal compound in a rock to make it worth extracting the metal.
- 5What does the process of extraction rely on?This is dependant on the reactivity series, the most reactive is at the top, and the least reactive is at the bottom. A more reactive element will displace a less reactive metal from its compounds. Carbon will also displace less reactive metals from their oxides.
- 6Why can carbon be used to extract metal oxides?Carbon is more reactive than each of the metal oxides therefore it can be used to extract them from their compounds.
- 7What happens when you react the metal oxide with carbon?It removes the oxygen from the metal oxide, leaving just the metal behind, forming carbon dioxide in the process. This is known as a reduction reaction.
- 8What is used to extract iron?A blast furnace, this is a large container made from steel, this is lined with fireproof brick to withstand the high temperatures inside.
- 9What raw materials are added to the furnace?Haematite - common iron ore containing mostly iron (III) oxide and sand.
Coke - this is made from coal and it is almost pure carbon, this acts as the reducing agent to remove the oxygen.
Limestone - added to remove impurities. - 10List the processes.Hot air is blown into the furnace, this makes the coke burn which heats the furnace and forms carbon dioxide. At the high temperatures, the carbon dioxide reacts with more coke to form carbon monoxide. This reacts with the iron oxide, removing the oxygen and reducing it to molten iron.
- 11How is cast iron formed?The molten iron is left to solidify in moulds, and it contains about 96% iron.
- 12How is steel formed using the molten iron?The iron is kept molten, then further impurities are removed, it is then mixed with other elements in order to change its properties.
- 13What is pig iron, and why is it not very useful?This is the iron produced in the blast furnace, however it contains impurities, mainly carbon - this makes it very brittle. These impurities can be removed through treatments.
- 14What are the properties of pure iron?It is very soft and easily shaped.
- 15What is an alloy?This is a metal which contains other elements in order to change its properties.
- 16How do alloys work?The atoms in pure iron are arranged in a regular pattern consisting of layers, this makes it easy for them to slide over one another, however when another element is introduced this structure is disrupted and it stops them from moving so easily.
- 17What is steel?An alloy of iron with carbon/other elements. The simplest steels are carbon steels, these are also the cheapest steels.
- 18What is a low-alloy steel?These are more expensive than carbon steels because they contain between 1% and 5% of other metals. These include nickel, chromium and titanium. Each give an alloy that is well-suited for a particular use, we use then to build long-span bridges and military armour plating.
- 19What is a high-alloy steel?These are even more expensive, as they contain a greater percentage of other metals still, chromium steels have between 12% and 15% chromium mixed with iron plus nickel, this provides strength and chemical stability.
- 20What are stainless steels?Chromium-nickel steels, they often used for cooking utensils and cutlery.
- 21Briefly explain some of the properties of copper.This is a soft, reddish coloured metal, it conducts heat and electricity well.
- 22How is bronze formed?By mixing copper with tin, but small amounts of other elements can also be added as well, this gives the allow properties which make it ideal to use for bearings where we want very low friction.
- 23How and why do we make brass?By alloying copper with zinc, brass is much harder than copper and it is workable. Hammering it into sheets means that it can be used to make musical instruments.
- 24What do we usually alloy gold with?Copper and silver, because otherwise it would be too soft for use as jewellery.
- 25Explain the term 'smart alloy'.If we bend or deform them into a different shape and then heat them, they return to their original shape, their technical name is shape memory alloys which describes the way they behave.
- 26When are SMAs used?In medical practice, they can be used to treat a broken bone and in treating orthodontics.
- 27Where are the transition metals used?As construction materials as they are malleable, we use them in heating systems and for electrical wiring because they conduct heat and electricity easily.
- 28State and briefly explain the two main methods used for the extraction of copper.In one method, they use sulphuric acid to produce copper sulphate before extracting the copper, the other process is smelting. We heat copper very strongly in air to produce crude copper, then we use the impure copper as anodes in electrolysis cells to make pure copper.
- 29What are the new ways of extracting copper?Instead of using chemicals, heat and electricity, scientists are using fungi and bacteria to extract the metals on a larger scale.
- 30Why are alternative methods preferred?It would be a lot cheaper and it would not have as much impact on the planet, we would also be able to extract copper from ores with very little copper (low grade ores).
- 31Why is aluminium used for making an aeroplane or the frame of a racing bicycle?Aluminium is a shiny metal with a relatively low density for a metal, it is also an excellent conductor of heat and electricity, however it does not corrode easily as its surface reacts with the oxygen in the air to form a thin layer of tough aluminium oxide.
- 32State the properties of an aluminium alloy.Harder, more rigid and stronger than pure aluminium, therefore they are used for cans, cooking foil and saucepans.
- 33Why makes titanium a useful metal?It is also a silvery metal, very strong and very resistant to corrosion, it produces an oxide layer to protect it - although it is dense than aluminium, it is less dense than most of the transition metals. It has a very high melting point, whereby it melts at about 1660 degree.
- 34Where is titanium used?It is very useful in nuclear reactors, it is used to make the pipes and other parts which must withstand high temperatures. It is also used in hip replacements.
- 35How is aluminium extracted?Using electrolysis, it is a very reactive metal therefore you cannot use carbon to displace it from its ore so we pass an electric current through molten aluminium oxide at high temperatures.
- 36How is titanium extracted?It is not particularly reactive, therefore we can produce it using displacement with carbon. But carbon makes it brittle so we have to use a more reactive metal, instead we use sodium or magnesium.
- 37What is the problem with using electrolysis?It is very expensive as it requires a lot of electricity and a very high temperature.
- 38What should you do with aluminium that you use?Recycle it.
- 39Explain 'phytomining'.Plants grow in a soil containing a low concentration of metal, and so the plants absorb it through their roots, these plants are then burned to produce plant ash containing a high concentration of the target metal.
- 40What is 'bioleaching'?Bacteria gain energy by digesting q compound of two metals, which separates it. The leachate (solution produced by the process) contains the metal, which can be extracted by filtering it.
- 41Briefly explain some of the advantages of mining for the extraction of metal from rocks.The products of which are useful, it also provides local people with jobs and brings miney into the economy - this means that public services such as the healthcare can be improved.
- 42Explain some of the disadvantages of mining for metal ores.It is bad for the environment as it causes noise, scarring of the environment and loss of habitat. Deep mine shafts can also be dangerous for a long time after they have been abandoned.
- 43Why is recycling metals so important?Mining and recycling of metals requires a lot of energy, most of which comes from burning fossil fuels - these are running out and the combustion of these fuels is leading to global warming and dimming.
- 44Give examples of why somebody should recycle.1) Recycling metals uses up only a fraction of the energy needed to extract them.
2) It saves money as extraction is quite expensive.
3) Recycling conserves the natural resources on our planet.
4) Cuts down pollution as a result of landfills.
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- Fichas sobre Extracting Metals, creado por Lauren Adams el 26/03/2016.
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