C1.2 Limestone and Building Materials

A decomposition reaction is one in which a compound breaks down into simpler compounds or elements.

Thermal means by heating it.

No atoms are lost or made when a thermal decompostion reaction takes place. The mass of the products, if they can be trapped, is the same as the mass of the reactants.

1. Limestone is a natural rock made mainly of calcium carbonate

Calcium Carbonate -heat strongly-> Calcium Oxide + Carbon Dioxide

CaCO3(s) --> CaO + CO2

2. Calcium Oxide + Water -slaking(add water)-> Calcium Hydroxide

CaO(s) + H2O(l) --> Ca(OH)2(s)

3. Calcium Hydroxide + more water -shake with water and filter, use solution-> Calcium Hydroxide solution

Ca(OH)2 + aq(solvent water) --> Ca(OH)2(aq) 

4. Calcium Hydroxide solution + Carbon Dioxide(bubble through CO2) --> Calcium Carbonate + Water

Ca(OH)2 + CO2 --> CaCO3(s) + H2O  limestone looks cloudy

As a building material:

• Houses and road foundation (direct use)
• Limestone grinded up with clay and mix to powder -heat, rotating kiln-> cement
• Cement is laid to make paths or fill cracks in buildings
• Cement + sand -mix-> mortar (to hold together bricks). 
• Cement + sand + agregat(gravel) -mix-> concrete. Concrete is used to make buildings. It is cheaper than limestone.
• Limestone can be turned into calcium hydroxide by adding heat and water. Calcium Hydroxide neutralises acid farm soil, neutralises excess acidity

Advantages

• Used for buildings
• Creates jobs
• Improve local roads

Disadvantages

• Leaves visual scars on landscape
• Explosives used make noise and dust
• Scare off wildlife
• Noise pollution
• Looks ugly
• Destroys animal wildlife