chemistry C1 (2)

How is limestone made?

1. when fish and other organisms that live in the sea die, their remains sink to the bottom of the sea

2. their skeletons and the calcium of their shells form layers on the sea floor

3. with many years passing, the layers become compressed, they decome the thick layers of rock known as limestone

4. these are the main rocks that we see because they are formed on the surface of the earth, they are usually soft

The limestone cycle

• when limestone is heated strongly, it decomposes to give solid quicklime and carbon dioxide
• when a small amount of water is added to quicklime it gives slaked lime
• if a lot of water is added to the slaked lime a solution of lime water is formed
• if carbon dioxide is bubbled through lime water limestone is formed again, along with water

• calcium carbonate = calcium oxide (s) + carbon dioxide (g)
• CaCO3 = Ca + CO2
• calcium oxide (s) + water (l) = calcium hydroxide (s)
• CaO + H2O = Ca(OH)2
• calcium hydroxide (aq) + carbon dioxide (g) = water + calcium carbonate
• Ca(OH)2 + CO2 = CaCO3 + H2O

Uses of limestone

• limestone can be added directly to soils to help combat acid and alter their pH
• buildings have been made out of limestone for thousands of years
• limestone maybe added to cosmetics and toothpaste as a bulking agent
• …