Limestone and Building Materials

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  • Created by: Hope
  • Created on: 09-06-13 11:47

Thermal Decomposition

Limestone is mainly calcium carbonate, CaCo3, which when heated breaks down to form calcium oxide and carbon dioxide. 

Calcium oxid reacts with water to produce calcium hydroxide. Limestone and its products have many uses, including being used to make cement, mortar and concrete

Thermal Decompostition

  • Calcium carbonate breaks down when heated strongly. This reaction is called thermal decompostion. Here are the equations for the thermal decompostion of calcium carbonate:
  • calcium carbonate >heat> calcium oxide + carbon dioxide// CaCO3 >heat> CaO+CO2
  • Other metal carbonates decompose in the same way including, sodium carbonate, magnesium carbonate and copper carbonate e.g.
  • Copper carbonate >heat> copper oxide + carbon dioxide// CuCO3 >heat> CuO+ CO2

Metals high up in the reactivity series (such as sodium, calcium and magnesium) have carbonates that need a lot of energy to decompose them.

Not all the carbonates of group 1 metals decompose at the temperatures reached by a bunsen burner

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Thermal Decomposition 2

Metals low down in the reactivity series, such as copper, have carbonates that are easily decomposed. This is why copper carbonate is used at school to show thermal decomposition. Its colour change from green copper carbonate to black copper oxide is easy to see(http://www.bbc.co.uk/schools/gcsebitesize/science/images/7_thermal_decomposition_v2.gif)

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Products from Calcium Carbonate

Making Calcium Oxide 

  • If calcium carbonate is heated strongly, it breaks down to form calcium oxide and carbon dioxide. 
  • Calcium oxide is yellow when hot but white when cold.
  • Calcium carbonate >heat> calcium oxide + carbon dioxide 
  • CaCO3 >heat> CaO + CO2 - This is a thermal decomposition reaction

Making Calcium Hydroxide

  • Calcium oxide reacts with water to form calcium hydroxide, which is an alkali.
  • Calcium oxide + water > calcium hydroxide
  • CaO + H2O > Ca(OH)2
  • A lot of heat is produced in this reaction, which may even cause water to boil
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Products from Calcium Carbonate

Making Calcium Oxide 

  • If calcium carbonate is heated strongly, it breaks down to form calcium oxide and carbon dioxide. 
  • Calcium oxide is yellow when hot but white when cold.
  • Calcium carbonate >heat> calcium oxide + carbon dioxide 
  • CaCO3 >heat> CaO + CO2 - This is a thermal decomposition reaction

Making Calcium Hydroxide

  • Calcium oxide reacts with water to form calcium hydroxide, which is an alkali.
  • Calcium oxide + water > calcium hydroxide
  • CaO + H2O > Ca(OH)2
  • A lot of heat is produced in this reaction, which may even cause water to boil
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Uses of Limestone

Limestone is a type of rock, mainly composed of calcium cabronate. Limestone is quarried (dug out of the ground) and used as a building material. It is also used in the manufacture of cement, mortat and concrete.

Reactions with Acids

  • Carbonates react with acids to produce carbon dioxide, a salt and water.e.g
  • Calcium carbonate + hydrochloric acid > carbon dioxide + calcium chloride + water
  • CaCO3 + 2HCl > CO2 + CaCl2 + H2O
  • Since limestone is mainly calcium cabronate is damaged by acid rain.
  • Sodium carbonate, magnesium carbonate, zinc carbonate and copper carbonate also react with acids : they fizz when in contact with acids and the carbon dioxide released can be detected using limewater.

Calcium Hydroxide

When limestone is heated strongly, the calcium cabronate it contains decomposes to form calcium oxide. This reacts with water to form calcium hydroxide, which is an alkali. Calcium hydroxide is used to neutralise excess acidity,, for example in lakes and soils affected by acid rain

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Uses of Limestone 2

Cement, Mortar and Concrete

Cement is made by heating powdered limestone with clay. Cement is an ingrediant in mortar and concrete.

  • Mortar used to join bricks together, is made by mixing cement with sand and water
  • Concrete is made by mixing cement with sand and water and aggregate (crushed rock)

Advantages and Disadvantage of various building materials

  • Limestone, cement and mortar slowly react with carbon dioxide dissolved in rainwater and wear away. This damages walls made my limestone and leaves gaps between bricks in buildings 
  • Pollution from burning fossil fuels makes the rain more acidic than it shoul.d be, and this acid rain makes these problems worse.
  • Concrete can be easily formed into different shapes before it sets hard.
  • It is strong when squashed but weak when bent or stretched.
  • Concrete can be made much stronger by reinforcing it with steel.
  • Some people think that concrete buildings and bridges are unnatractive
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Quarrying

Advantages of the Limestone industry

  • Limestone is a valuable natural resource, used to make things such as glass and concrete
  • Limestone quarrying provides employment opportunities that support the local economy and towns around the quarry

Disadvantages of the Limestone industry

  • Limestone quarries are visable from long distances and may permanently disfigure the local environment
  • Quarrying is a heavy industry that creates noise and heavy traffic, which damages peoples quality of life.
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