C1 Chemistry Unit 2: Rocks and building materials

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C1 2.1: Limstone and its uses

  • Limestone is mainly made of calcium carbonate.
  • Limestone is mainly used in the building industry.
  • The chemical formula for limestone is CaCO3.
  • When we heat limestone strongly the calcium carbonate breakes down to form calcium oxide and carbon dioxide is also produced. (CaCO3 - CaO + CO2)
  • Breaking down a chemical by heating is called thermal decomposition.
  • Calcium oxide can be produced using a rotary kiln, the kiln is filled with crushed limestone and heated strongly using a supply of hot air. Calcium oxide comes out of the bottom of the kiln and waste gases made come out through the top of the kiln.
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C1 2.2: Reactions of carbonates

  • Buildings and statues made of limestone are damged by acid rain, limestone is mainly made of calcium carbonate which reacts with acid and gives off a gas.
  • Carbon dioxide turns limewater cloudy.
  • When the CO2 reacts with the limewater tiny solid particles of insoluble calcium carbonate are formed as a precipitate.
  • Calcium hydroxide(lime water) + carbon dioxide - calcium carbonate(an insoluble preciptate) + water.
  • Ca(OH)2 + CO2 - CaCO3 + H2O
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C1 2.3: The 'limestone reaction cycle'

When water is added to calcium oxide it reacts to produce calcium hydroxide.

Calcium oxide + water - calcium hydroxide, CaO + H2O - Ca(OH)2

Calcium hydroxide is an akali which reacts with acids in a neutralisation reaction.

(http://image.slidesharecdn.com/c1-140919062042-phpapp01/95/c12-limestone-12-638.jpg?cb=1411107730)

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C1 2.4: Cement and concrete

  • When you heat limestone with clay in a kiln produces cement.
  • Mortar is made by mixing cement and sand with water.
  • Concrete is made by mixing crushed rocks, cement and sand with water.
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C1 2.5: Limestone issues

  • Quarrying scares the landscape and blasting which is used to dislodge limestone scares away the local wildlife and disturbs residents.
  • Eventually a huge crater is left which can be filled with water or used as a landfill site.
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