C1 2.1 - 2.5 - Rocks and Building Rocks

Limestone

Limestone is a compound of calcium carbonate. We use it for hundreds of things, from building to acidity regulation. It was formed millions of years ago in the sea from the bodies of dead sea creatures. It is now found worldwide. We dig it out of quarries,

It is so popular as a building material, as we can shape it very easily into things such as bricks, blocks and statues. If we turn the limestone into powder, we can create cement by heating the powdered limestone with powdered clay. This, in turn, can be made into concrete if we mix the cement with water, crushed rock and sand. The reaction is very slow. This cement is known as lime mortar. It can hold bricks and stone together very strongly, but it will not set whilst in contact with water. However, after mixing the cement with other minerals, we made Portland cement. After 200 years, we are still using it.

After adding crushed rock or small stones (known as aggregate), we can create a building material called concrete. It is strong and very resistant against forces that squash or crush it. If we pour it around steel bars and rods, we create reinforced concrete. This is very resistant against forces that pull it apart.

The formula for calcium carbonate is CaCO3.

If we vigorously heat the CaCO3, we produce calcium oxide (also known as Quicklime) and CO2 (carbon dioxide). This method of breaking down a material by heating it is called thermal decomposition.

Thermal decomposition of CaCO3:

CaCO3 -> CaO + CO2

Calcium carbonate -> Calcium Oxide + Calcium Carbonate

We use CaO in the building and agricultural industry.

In industry, we produce a lot of CaO in something called a rotary kiln (also known as a lime kiln). It looks like a large oil barrel turned on it's side with t statues and they are missing features, such as the nose. There is a test for the existence of CO2. You put a tube in the reaction to catch any waste…