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LimestoneWhat you need to know |
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Limestone and its usesLimestone is mainly composed of the compound calcium carbonate (CaCO3). Limestone is a sedimentary rock which was formed from the shells of sea creatures that lived millions of years ago. Limestone is quarried and can be used to produce cement, glass and concrete. CementLimestone is heated with clay to make cement in a rotary kiln. The rotary kiln is heated to about 900°C and the calcium carbonate undergoes thermal decomposition to produce calcium oxide. calcium carbonate → calcium oxide + carbon dioxide CaCO3 → CaO + CO2 The energy costs are high and this produces carbon dioxide (CO2). This contributes to global warming and climate change. MortarCement is mixed with sand to make mortar. ConcreteCement is mixed with sand and aggregate to make concrete which can resist crushing or squashing forces. The concrete can be strengthened by adding steel rods to form reinforced concrete. The Lime CycleCalcium carbonate Calcium carbonate can be decomposed by heating (thermal decomposition) to make calcium oxide and carbon dioxide. calcium carbonate → calcium oxide + carbon dioxide CaCO3 → CaO + CO2 The carbonates of magnesium, copper, and zinc decompose on heating in a similar way. However, the more reactive the metal carbonate is the more heat energy is required. Calcium oxideCalcium oxide (slaked lime) reacts with water to produce calcium hydroxide (limewater). calcium oxide + water → calcium hydroxide CaO(s) + H2O(l) → Ca(OH)2(s) Calcium hydroxide is an alkali that can be used in the neutralisation of acids. Calcium hydroxideA solution of calcium hydroxide (limewater) reacts with carbon dioxide to produce calcium carbonate. calcium hydroxide solution + carbon dioxide → calcium carbonate + water Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l) Limewater (calcium hydroxide) is used as a test for carbon dioxide. Carbon dioxide turns limewater cloudy/milky. Reaction of carbonatesCarbonates react with acids to produce a salt, carbon dioxide and water. For example: Calcium carbonate + hydrochloric acid → calcium chloride + carbon dioxide + water. Limestone is damaged by acid rain. Limestone issuesLimestone QuarryingIn order to get the limestone, explosives are used to blast it from quarries. Transported using large lorries to be processed.
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Describe limestone and its uses Describe thermal decomposition of limestone Describe what happens when calcium oxide reacts with water Draw a diagram to represent the limestone cycle Describe what happens at a quarry Identify problems associated with quarrying Consider the views of different people affected by quarrying |