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Products from rocks (summary of the AQA module)
 

Products from rocks (summary of the AQA module)

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AQA Products from Rocks summary

AQA Products from Rocks summary

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    Products from rocks (summary of the AQA module) Products from rocks (summary of the AQA module) Presentation Transcript

    • Products from rocks Revision summary 11 February 2011
    • Atoms, elements and compounds
      • All substances are made up of atoms .
      • Elements contain only one type of atom.
      • The atom has a central core called the nucleus and this is surrounded by fast moving electrons .
      • Atoms form chemical bonds by giving taking or sharing electrons – the new substance formed is a compound .
      • All atoms have their own symbols and are shown on the periodic table.
      1
    • Chemistry of limestone
      • Limestone is calcium carbonate (CaCO 3 ), it is a solids white compound.
      • Limestone is used in buildings.
      • Limestone decomposes(thermal decomposition) when heated into quicklime or calcium oxide (CaO) and carbon dioxide (CO 2 ).
      • Other metal carbonates also decompose on heating.
      2
    • Quicklime and slaked lime
      • If water is added to quicklime (CaO) a lot of heat is released and slaked lime or calcium hydroxide Ca(OH) 2 is formed.
      • Slaked lime, sand and water form mortar. This has been used in building for thousands of years.
      • The reaction is:
      • Slaked lime + CO 2 = calcium carbonate + water .
      3
    • Cement, concrete and glass
      • Heating limestone with clay in a kiln produces cement – this hardens much faster than slaked lime mortar.
      • Concrete is a mixture of stones, sand cement and water. It can be reinforced with steel bars and is very strong.
      • Glass is made by heating limestone, sand and sodium carbonate.
      4
    • Extracting metals
      • Metals are usually found combined with other elements in ores but a few like gold and silver are found naturally (native state).
      • The reactivity series shows a list of metals from most reactive to least reactive.
      • Metal oxides can be reduced to the metal and carbon dioxide using carbon.
      • Metal oxide + carbon = metal + carbon dioxide
      5
    • Extracting iron
      • Iron ore (haematite or iron oxide) can be extracted with carbon (coke) in a blast furnace.
      • Limestone is also added to remove sand in the mix as it forms slag.
      • Reactions are:
      • C + O 2 =CO 2
      • CO 2 + C = CO
      • Fe 2 O 3 + 3CO = 2Fe + 3CO 2
      6
    • Properties of iron and steel
      • Iron made in a blast furnace is 96% pure, it is called pig iron and is very brittle.
      • The carbon is removed from the impure iron and other elements are added to make steel.
      • Steels made with chromium and nickel as alloys are called stainless steel. This type of steel does not rust and is very hard.
      7
    • Using alloys
      • Bronze is made from copper and tin – low friction metal.
      • Brass is made from copper and zinc and is very hard and strong.
      • Gold is alloyed to make it harder.
      • Smart alloys are able to retain their shape – they are used in medicine and dentistry to help move teeth and bones into the correct position.
      8
    • Transition metals
      • The transition metals area large block of metals in the middle of the periodic table.
      • Their properties include being good conductors of heat and electricity, hard, strong and malleable (bend into shapes).
      • These properties make these metals ideal for use in construction and manufacturing transport vehicles.
      9
    • Copper
      • Copper is the most useful metal in conduction of electricity.
      • It is extracted form its ore by reacting with sulphuric acid or smelting (heating) followed by electrolysis.
      • The above processes use vast amounts of heat and electricity so are not environmentally friendly and expensive.
      • New methods using bacteria or fungi are being investigated.
      10
    • Aluminium
      • Aluminium has a very low density and is a good conductor or heat and electricity.
      • Aluminium does not corrode easily but in its natural state is not very strong. However when it is alloyed with other metals it becomes harder and stronger.
      • Aluminium is a very reactive metal so it has to be extracted from it bauxite (aluminium oxide) ore by electrolysis – this an expensive process.
      11
    • Titanium
      • Titanium is a silvery white, strong and non corrosive metal.
      • Its very high melting point (1660oC) makes it especially useful.
      • It is produced by displacement by a more reactive metal such as magnesium or sodium.
      • It is used for jet engines, aircraft bodies, in nuclear reactors and for human joint replacements.
      12
    • Fuels from crude oil
      • Crude oil contains a mixture of hydrocarbon molecules.
      • Most of the hydrocarbons in crude oil are alkanes – these have the general formula C n H 2n+2 .
      • Since there are no carbon carbon double bonds in alkanes the molecules are said to be saturated (cannot bond onto any more atoms)
      13
    • Fractional distillation
      • Crude oil is separated into different fractions, containing molecules of different sizes by fractional distillation.
      • Small molecules have lower boiling points, are of low viscosity (runny), more volatile and flammable, so they are better fuels.
      • Crude oil vapour is fed into a fractionating column with lower boiling point gases coming off high up the column.
      14
    • Burning fuels
      • When a fuel is burnt in an oxygen rich environment carbon dioxide and water vapour is produced.
      • If too little oxygen is present poisonous carbon monoxide (CO) is produced.
      • Fuels also produce sulphur dioxide which make acid rain and nitrogen dioxide as well as carbon particles (particulates)
      15
    • Cleaner fuels
      • Carbon dioxide gas from burning fuels is a greenhouse gas. This gas warms the Earth by reducing heat loss from the atmosphere.
      • The pollution produced by gases such as carbon monoxide, sulphur dioxide and nitrogen oxides can be reduced by treating these gases as they are produced – examples are catalytic converters and desulphurisation chemicals.
      16