Chemistry - C1.2 - Rocks and Building Materials

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C1.2.1 - Limestone and Its Uses

  • Limestone is quarried as it has many uses - it can be used for building as it is used to make calcium oxide and cement
  • Concrete - cement, sand, aggregate and water
  • Limestone - calcium carbonate CaCO3 - when heated -> decomposes -> calcium oxide (quicklime) and CO2 - this is done on a large scale in kilns and called thermal decomposition
  • CaCO3 -> CaO + CO2
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C1.2.2 - Reactions of Carbonates

  • Metal carbonates - react in similar ways when heated or with acids, decompose to metal oxide and CO2 when heated strongly enough - bunsen burners aren't hot enough to decompose sodium or potassium carbonate
  • Carbonate + acid -> salt + water + CO2
  • Limestone - damaged by acid rain - CaCO3 reacts with acid in the rain
  • Calcium hydroxide solution - limewater - used to test for CO2 - turns cloudy as reacts with CO2 to produce insoluable CaCO3
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C1.2.3 - The 'Limestone Reaction Cycle'

  • CaCO3 ->heat-> CaO + CO2
  • CaO + H2O -> Ca(OH)2
  • Ca(OH)2 + CO2 -> CaCO3
  • Calcium hydroxide - alikali - used to neutralise acids - used by farmers to neutralise soil and industry to neutralise gases, not very soluable in water - dissolves slightly to make limewater
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C1.2.4 - Cement and Concrete

  • Cement - limestone mixed with clay, heated strongly in kiln, ground into fine powder
  • Mortar - cement mixed with sand and water, used to hold bricks and blocks in buildings together
  • Concrete - aggregate, cement, sand and water, poured into moulds and then sets to form hard solid
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C1.2.5 - Limestone Issues

  • Limestone is needed for building - cement and concrete are used in most buildings
  • Disadv of limestone -
      - quarrying limestone - negative impacts on environment and people living near quarries
      - cement - uses lots of heat, therefore energy,  large area of land needed
      - other issues - dust, noise, traffic, loss of habitat for wildlife
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