Products from rocks (summary of the AQA module)


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AQA Products from Rocks summary

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Products from rocks (summary of the AQA module)

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