C1.2 Limestone and building materials

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Calcium Carbonate

Calcium carbonate has the chemical formula CaCO3 and has any uses. Limestone, which is mainly calcium carbonate is extracted from the ground by quarrying and can be used as a building material. Calcium carbonate thermally decomposes to form calcium oxide and carbon dioxide.

The calcium oxide produced will react with water to produce calcium hydroxide Ca(OH)2. Calcium hydroxide can be used to neutralise acids e.g it is used to neutralise acidic soil in farming

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Calcium hydroxide produced by the reaction of calcium oxide and water can be dissolved in water to produce calcium hydroxide solution more commonly known as limewater. Limewater is a test to see if carbon dioxide is present, if CO2 is found the limewater will go cloudy. This is because there has been a reaction between the limewater and carbon dioxide;

Calcium hydroxide + carbon dioxide => calcium carbonate + water

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Limewater cycle

Calcium carbonate [CaCO3] + heat => Carbon dioxide + calcium oxide [CaO]

Calcium oxide [CaO] + water => Calcium hydroxide [Ca(OH)2]

Calcium hydroxide [Ca(OH)2] + more water + filter => calcium hydroxide solution [Ca(OH)2]

calcium hydroxide solution [Ca(OH)2] + carbon dioxide => Calcium carbonate [CaCO3

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Cement, mortar and concrete

Cement is made when limestone is heated with clay.

Mortar is made when cement is mixed with sand.

Concrete is made when cement is mixed with sand and aggegate.

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Pros and Cons of quarrying limestone

Advantages of limestone;

  • used for may different things like buildings and statues
  • fire resistant materials
  • limestone does not rot
  • It does not corrode as fast as metals
  • quarrying provides jobs and adds to the local economy
  • limestone is widley available and cheap
  • old quarrying can be converted into nature reserves


  • large quarries are not aesthetically pleasing
  • transport causes high CO2 emissions and loud noises
  • habitats destroyed
  • accidents in the quarry causing injury
  • high levels of energy used for drills and transport
  • particles released into the atmosphere cause illness
  • concrete blocks are expensive
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Carbonate reactions and thermal decomposition

When metal carbonates react with an acid they always form a salt, water and carbon dioxide, this can be shown in a general equation;

Metal carbonate + acid => salt + water + carbon dioxide

When calcium carbonate is heated it thermaly reacts to produce calcium oxide and carbon dioxide. Other metal carbonates decompose on heating in a similar way;

Metal carbonate + heat => metal oxide + carbon dioxide

Metals high up in the reactivity series e.g. sodium and calcium have carbonates that need a lot of enegy to decompose. Therefore sodium carbonate will not decompose at tempuratures reached by a bunsen burner. Copper carbonate on the other hand will as it is lower down in the reactivity series

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