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'
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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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