and its uses

1
and its uses
Limestone
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 in quarries
• In Britain about 150 million tonnes of limestone
  are quarried each year
• Limestone is the compound calcium carbonate
• Its formula is CaCO3
• Limestone can be chemically changed into other
  things

5
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 have broken down into
  calcium oxide and carbon dioxide
• We call calcium oxide quicklime

6
A word equation for this reaction

• Calcium heat calcium
  carbon
• Carbonate oxide dioxide

7
Reacting quicklime with water

• Calcium oxide (quicklime) is a strong alkali
• It reacts with water to form calcium hydroxide
• Calcium hydroxide is also known as slaked lime

8
A word equation for this reaction

• calcium water calcium
  
• oxide
  hydroxide

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
• 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

11
A word equation for this reaction

• calcium carbon calcium water
• hydroxide dioxide carbonate

12
The Limestone Cycle

• These reactions all make up the
• limestone cycle.

13
The limestone cycle
limestone
carbon dioxide
heat
quicklime
limewater
more water
water
Slaked lime
14
Tasks

• Use the worksheet called The Limestone
• Cycle to fill in the gaps and complete the
• equations for the reactions of limestone.
• Copy out The Limestone Cycle.
• Answer questions 1-5 on the next worksheet
• using the information given and your own
• Knowledge. Afterwards copy out the
• summary.

15
HOMEWORK

• Complete the worksheet on
• Questions on Limestone
• for next lesson.

16
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