C1 Chemistry Unit 2: Rocks and building materials

• Limestone is mainly made of calcium carbonate.
• Limestone is mainly used in the building industry.
• The chemical formula for limestone is CaCO3.
• When we heat limestone strongly the calcium carbonate breakes down to form calcium oxide and carbon dioxide is also produced. (CaCO3 - CaO + CO2)
• Breaking down a chemical by heating is called thermal decomposition.
• Calcium oxide can be produced using a rotary kiln, the kiln is filled with crushed limestone and heated strongly using a supply of hot air. Calcium oxide comes out of the bottom of the kiln and waste gases made come out through the top of the kiln.

• Buildings and statues made of limestone are damged by acid rain, limestone is mainly made of calcium carbonate which reacts with acid and gives off a gas.
• Carbon dioxide turns limewater cloudy.
• When the CO2 reacts with the limewater tiny solid particles of insoluble calcium carbonate are formed as a precipitate.
• Calcium hydroxide(lime water) + carbon dioxide - calcium carbonate(an insoluble preciptate) + water.
• Ca(OH)2 + CO2 - CaCO3 + H2O

When water is added to calcium oxide it reacts to produce calcium hydroxide.

Calcium oxide + water - calcium hydroxide, CaO + H2O - Ca(OH)2

Calcium hydroxide is an akali which reacts with acids in a neutralisation reaction.

• When you heat limestone with clay in a kiln produces cement.
• Mortar is made by mixing cement and sand with water.
• Concrete is made by mixing crushed rocks, cement and sand with water.

• Quarrying scares the landscape and blasting which is used to dislodge limestone scares away the local wildlife and disturbs residents.
• Eventually a huge crater is left which can be filled with water or used as a landfill site.