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1. The limestone cycle
2. Learning Objectives By the end of the lesson I will be able to:
Carry out thermal decomposition of calcium carbonate
Draw a flow diagram of the limestone cycle
Write balanced chemical equations for reactions in the limestone cycle
3. Heating limestone When limestone (calcium carbonate) is heated, it breaks down (decomposes)
When something breaks down with heat we call this reaction
Calcium carbonate breaks down into calcium oxide (quicklime) and carbon dioxide
4. Thermal decomposition of limestone Calcium heat calcium carbon
Carbonate oxide dioxide
5. Reacting quicklime with water Calcium oxide (quicklime) is a strong alkali
It reacts with water to form calcium hydroxide Ca(OH)2
Calcium hydroxide is also known as slaked lime
6. Uses for quicklime Making cement, mortar and concrete.
Decomposing rotting bodies in mass graves and reducing the smell !
7. Making Slaked Lime
calcium + water calcium
CaO + H2O Ca(OH)2
8. Uses for slaked lime To neutralise acidic soils, and to break up the soil so that plants can grow well
To neutralise lakes which have been polluted by acid rain
9. Limewater Limewater is a solution of calcium hydroxide
It is used to test for carbon dioxide
We breathe out a lot of carbon dioxide
If we blow through a straw into limewater it will change from clear to milky-white
The substance formed in this reaction is insoluble calcium carbonate
10. Testing for carbon dioxide
calcium + carbon calcium + water
hydroxide dioxide carbonate
Ca(OH)2 + CO2 CaCO3 + H2O
11. The Limestone Cycle These reactions all make up the
12. Task: Use the worksheet called The Limestone
- fill in the gaps and complete the
equations for the reactions of limestone.
Stick into your books.