C1 Metals and their uses

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  • Metals and their uses
    • Extracting metals
      • A metal ore is a rock which contains enough metal to make it worthwhile extracting the metal from it
        • In many cases the ore is an oxide of the metal (e.g. the main aluminium ore is bauxite, which is aluminium oxide)
      • Most metals need to be extracted from their ores using a chemical reaction
        • A metal ore is a rock which contains enough metal to make it worthwhile extracting the metal from it
          • In many cases the ore is an oxide of the metal (e.g. the main aluminium ore is bauxite, which is aluminium oxide)
        • A metal can be extracted from its ore chemically - by reduction with carbon or by electrolysis
          • This depends on the metal's place in the reactivity series
            • Metals above carbon in the reactivity series are extracted using electrolysis
              • Electrolysis can also be used to purify the extracted metal
                • Some ores may have to be concentrated before the metal is extracted - this just involves getting rid of the unwanted rocky material
              • This process is a lot more expensive than reduction with carbon because it uses a lot of energy
              • Electrolysis involves  passing an electric current through a molten metal compound, splitting it into its metal and non-metal elements
                • Electrons are pulled off metal atoms at the anode, causing them to go into the solution as metal ions
                  • Metal ions are attracted to the cathode, where they gain ellectrons and turn into metal atoms
            • Metals below carbon in the reactivity series are extracted by reduction with carbon
              • The metal oxide is reduced by heating it in a furnace with carbon
                • The carbon reacts with the metal oxide and displaces the metal, leaving carbon dioxide and the metal by itself
              • When are ore is reduced, oxygen is removed from it
        • Some ores may have to be concentrated before the metal is extracted - this just involves getting rid of the unwanted rocky material
      • The economics of metal extraction can change over time
        • If the market price of a metal drops a lot, it might not be worth extracting it
          • If the price increases a lot then it might become worth extracting more of it
        • As technology improves, it becomes possible to extract more metal from a sample of rock than was originally possible
          • This means it might now be worth extracting metal that wasn't worth extracting in the past
    • Copper extraction
      • A displacement reaction can be used to extract copper
        • More reactive metals react more vigorously than less reactive metals
          • If you put a reactive metal into the solution of a dissolved metal compound, the reactive metal will replace the less reactive metal
            • This is because the more reactive metal bonds more strongly to the non-metal bit of the compound and pushes out the less reactive metal
        • For example, scrap iron can be used to displace copper from solution
          • This is really useful because iron is cheap but copper is expensive
          • If some iron is put in a solution of copper sulphate, the more reactive iron will 'kick out' the less reactive copper from the solution
            • You end up with iron sulphate solution copper metal
      • The supply of copper-rich ores is limited, so it's important to recycle as much copper as posible
      • The demand for copper is growing and this may lead to shortages in the future
      • Scientists are looking into new ways of extracting copper from low-grade ores (ores that only contain small amounts of copper) or from the waste that is currently produced when copper is extracted
        • Bioleaching uses bacteria to separate copper from copper sulphide
          • The bacteria gets energy from the bond between copper and sulphur, separating out the copper from the ore in the process
            • The leachate (the solution produced by the process) contains copper, which can be extracted, e.g. by filtering
        • Phytomining involves growing plants in soil that contains copper
          • The plants can't use or get rid of the copper so it gradually builds up in the leaves
            • The plants can be harvested, dried and burned in a furnace
              • The copper can be collected from the ash left in the furnace
        • These new methods of extraction have a much smaller impact on the environment than traditional methods of copper mining, but the disadvantage is that they're slow
    • Impacts of extracting metals
      • Metal extraction can be bad for the environment
        • People have to balance the social, economic and environmental effects of mining the ores
          • Most of the issues are exactly the same as those to do with quarrying limestone
            • So mining metal ores is good because it means that useful products can be made
              • It also provides local people with jobs and brings money into the area, meaning services such as transport and health can be improved
            • Mining ores is bad for the environment as it causes noise, scarring of the landscape and loss of habitats
              • Deep mine shafts can also be dangerous for a long time after the mine has been abandoned
      • Reycling metals is important
        • Mining and extracting metals takes lots of energy, most of which comes from burning fossil fuels
          • Fossil fuels are running out so it's important to conserve them. Not only this, but burning them contributes to acid rain, global dimming and climate change
            • Recycling metals only uses a small fraction of the energy needed to mine and extract new metal
              • Mining and extracting metals takes lots of energy, most of which comes from burning fossil fuels
                • Fossil fuels are running out so it's important to conserve them. Not only this, but burning them contributes to acid rain, global dimming and climate change
                  • Recycling metals only uses a small fraction of the energy needed to mine and extract new metal
                    • For example, recycling copper only takes 15% of the energy that's needed to mine and extract new copper
                • Energy doesn't come cheap, so recycling saves money too
              • For example, recycling copper only takes 15% of the energy that's needed to mine and extract new copper
          • Energy doesn't come cheap, so recycling saves money too
        • There's a finite amount of each metal in the Earth, and recycling conserves these resources
        • Recycling metal cuts down on the amount of rubbish that gets sent to landfill
          • Landfill takes up space and pollutes the surroundings
    • Properties of metals
      • All metals have some fairly similar basic properties
        • Metals are strong but they can be bent or hammered into different shapes (malleable)
        • They're great at conducting heat
        • They conduct electricity well
      • Metals (and especially transition metals) have loads of everyday uses because of their properties
        • Their strength and malleability makes them handy for making into things like bridges and car bodies
        • Their conductivity makes them great for making things like electrical wires and saucepan bases
      • Metals are very useful structural materials, but some corrode when exposed to air and water, so they need to be protected, e.g. by painting
        • If metals corrode, they lose their strength and hardness
      • Metals can get 'tired' when stresses and strains are repeatedly put on them over time
        • This is known as metal fatigue and leads to metals breaking, which can be very dangerous, e.g. in planes
      • Copper is a good conductor of electricity, so it's ideal for drawing out into electrical wires
        • It's hard and strong but can be bent, and it doesn't react with water
      • Aluminium is corrosion-resistant and has a low density
        • Pure aluminium isn't particularly strong, but it forms hard, strong alloys
      • Titanium is a low density metal, which is very strong and corrosion-resistant
    • Alloys
      • See

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