Limestone and its Uses

Limestone is a sedimentary rock made up of mainly calcium carbonate. 
It’s cheap and easy to obtain.
Some uses:
1) Building materials – limestone can be quarried and cut into blocks to be used in building.However, it is badly affected by acid rain.
2) Glass making – glass is made by mixing limestone with sand and sodium carbonate: 
Limestone + sand + sodium carbonate ----> glass
3) Cement making – limestone can be “roasted” in a rotary kiln to produce dry cement. It’s then mixed with sand and gravel to make concrete

If soil is too acidic crops will fail. Limestone can also be used as a neutralising agent. 
There are two reactions to know:
1) Firstly, a THERMAL decomposition reaction is used to break the calcium carbonate down into calcium oxide (quicklime) and carbon dioxide: 
Calcium Carbonate ----heat> calcium oxide + carbon dioxide
2) This is then “slaked” with water to produce calcium hydroxide (“slaked lime”): 
Calcium Oxide ----water> calcium hydroxide 
Calcium hydroxide is alkaline and is used to neutralise acidic soil.

Key Words:

Quarry

Thermal Decomposition

Cement

Concrete

Questions:

1) What's the word equation for the thermal decomposition of calcium carbonate?

2) How is cement made?

What you should know:

• 2.8 Have an understanding of the balance between the demand for limestone and the economic, environmental and social effects of quarrying it.
• 2.9 Have an understanding of the commercial need for quarrying calcium carbonate on a large scale, as a raw material, for the formation of glass, cement and concrete.
• 2.10 Be able to describe the thermal decomposition of calcium carbonate into calcium oxide and carbon dioxide.