1. Limestone
and its uses

2. What is limestone? It is a sedimentary rock
It was formed mainly from sea shells
It is the compound called calcium carbonate
It is a useful raw material

3. What can limestone be used for?
Building walls
Building houses
Limestone is also used to make cement and concrete
Neutralising excess acid in lakes or soils

4. More about limestone
Limestone is dug up out of the ground from lime stone hills.
In Britain about 150 million tonnes of limestone are used each year
Limestone is the compound calcium carbonate
It’s formula is CaCO3
Limestone can be chemically changed into other things

5. Thermal decomposition reaction
Heating limestone
When limestone (calcium carbonate) is heated, it will break down (decompose)
When something breaks down with heat we call this reaction a ….
Thermal decomposition reaction
Calcium carbonate will be broken down into calcium oxide and carbon dioxide on heating.
We call calcium oxide quicklime

6. Equation for this reaction
Calcium heat calcium carbon
Carbonate oxide dioxide
CaCO3(s)  CaO(s) + CO2(g)

7. Reacting quicklime with water
Calcium oxide (quicklime) is a base
It reacts with water to form calcium hydroxide Ca(OH)2
Calcium hydroxide is also known as slaked lime

8. Equation for this reaction
calcium water calcium
oxide hydroxide
CaO(s) H2O(l)  Ca(OH)2(aq)

9. 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

10. Another use for calcium hydroxide
Calcium hydroxide is also called limewater
Limewater is used to test for the presence of carbon dioxide gas
Clear lime water (calcium hydroxide solution) turns white when carbon dioxide gas is passed through it.

11. Equation for this reaction
calcium carbon calcium water
hydroxide dioxide carbonate
Ca(OH)2(aq) + CO2(g)  CaCO3(s) + H2O(l)
(clear) (white ppt)

12. These reactions all make up the
The Limestone Cycle
These reactions all make up the
limestone cycle.

13. The limestone cycle THE END limestone carbon dioxide heat CaCO3
quicklime
limewater
CaO
Ca(OH)2
more
water
water
Slaked lime
Ca(OH)2
THE END