C1.2 Limestone and Building Materials

Limestone is a type of rock which is quarried and used as a building material. It is mostly calcium carbonate: CaCO3

Quicklime= clacium oxide, slaked lime= calcium hydroxide

Uses

• Raw material for cement, mortar, and concrete
• Neutralising rivers and acidic lakes
• As blocks and slabs for walls and pavements
• As aggregate (small lumps) for the base of roads and railways

Cement- heat limestone with clay

Mortar- mix cement with sand and water

Concrete- mix cement with sand, aggregate and water

Quarries

• New jobs created
• Limestone a valuable building material
• Fewer tourists
• Extra traffic
• Noise, visual and atmospheric pollution

Thermal decomposition

CaCO_{3 ->} CaO + CO₂

Carbonates of magnesium, copper, zinc and sodium decompose in the same way:

Metal carbonate -> metal oxide + carbon dioxide

Not all carbonates of metals in Group 1 decompose when heated with a bunsen flame.

Calcium Hydroxide

Calcium oxide reacts vigorously with drops of water to make a white solid- calcium hydroxide. A lot of heat is given out in the reaction. Calcium hydroxide is an alkali which can be used to neutralise acids.

calcium oxide + water → calcium hydroxide

CaO + H₂O → Ca(OH)₂

Limewater

Solution of calcium hydroxide in water, and is used as a test for CO2, which turns limewater cloudy. 

Ca(OH)2 + CO2 -> CaCO3 + H2O