Presentation on theme: "And its uses. 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."— Presentation transcript:
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
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
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 It’s formula is CaCO 3 Limestone can be chemically changed into other things
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
A word equation for this reaction Calcium heat calcium carbon Carbonateoxide dioxide
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
A word equation for this reaction calcium + water calcium oxide hydroxide
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
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
A word equation for this reaction calcium + carbon calcium + water hydroxide dioxide carbonate
The Limestone Cycle These reactions all make up the limestone cycle.
limestone Slaked lime quicklime limewater heat water more water carbon dioxide The limestone cycle
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.
HOMEWORK Complete the worksheet on Questions on Limestone for next lesson.
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