C1 Limestone and Building Materials

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  • Limestone and Building Materials
    • Limestone
      • Limestone is mainly calcium carbonate (CaCO3)
        • When heated it thermally decomposes into carbon dioxide (CO2) and calcium oxide (CaO)
          • When magnesium, copper, zinc and sodium carbonates are heated, they decompose the same way
            • Metals high up in the reactivity series (such as sodium, calcium and magnesium) have carbonates that need a lot of energy to decompose them.
              • A Bunsen burner can't reach a high enough temperature to thermally decompose some carbonates of Group 1 metals
          • Calcium carbonate also reacts with acid to form a calcium salt, carbon dioxide and water (calcium carbonate + sulphuric acid --> calcium sulphate + carbon dioxide + water)
            • The type of salt produced depends on the type of acid
              • Other carbonates that react with acids are magnesium, copper, zinc and sodium
            • This reaction means that limestone is damaged by acid rain
          • Calcium oxide reats with water to produce calcium hydroxide
            • Calcium hydroxide is an alkali which can be used to neutralise acidic soil in fields. Powdered limestone can be used for this too, but the advantage of calcium hydroxide is that it works much faster
              • Acidity in lakes and rivers caused by acid rain is also neutralised by limestone products
            • Calcium hydroxide in a solution is limewater, which can be used to test for carbon dioxide
      • Limestone provides  things that people want, like houses and roads
        • Chemicals used in making dyes, paints and medicines also come from limestone
      • Limestone is used in power station chimneys to neutralise sulphur dioxide, which is a cause of acid rain
      • Quarrying
        • Quarrying limestone can cause environmental problems
          • It makes huge ugly holes which permanently change the landscape
          • Quarrying processes, like blasting rocks apart with explosives, make lots of noise and dust in quiet, scenic areas
          • Quarrying destroys the habitats of animals and birds
          • The limestone needs to be transported away from the quarry - usually in lorries, which cause more noise and pollution
        • The quarry and associated businesses provide jobs for people and bring more money into the local economy
          • This can lead to local improvements in transport, roads, recreation facilities and health
        • Once quarrying is complete, landscaping and restoration of the area is normally required as part of the planning permisiion
    • Building Materials
      • Powdered limestone is heated in a kiln with powdered clay to make cement
        • Cement can be mixed with sand and water to make mortar, which is used to join bricks together
        • Concrete is made by mixing cement with sand and aggregate (water and gravel)
      • Limestone and concrete are used as building materials
        • Limestone is widely available and is cheaper than granite or marble. It's also a fairly easy rock to cut
        • Some limestone is more hard-wearing than marble, but it still looks attractive
        • Concrete can be poured into moulds to make blocks or panels that can be joined together
          • This is a very quick and cheap way of constructing buildings, but concrete is a very ugly building material
        • Limestone, concrete and cement don't rot when they get wet like wood does
          • They can't be gnawed away by insects or rodents either, and they're fire-resistant
        • Concrete doesn't corrode like lots of metals do
          • However, it has a fairly low tensile strength and can crack
            • If's much stronger when reinforced with steel bars

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