Transcript and its uses What is limestone? • It is a sedimentary rock • It was formed mainly from sea shells • It is the compound called.

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 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 CaCO3
• 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
Carbonate
heat
calcium
oxide
carbon
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
oxide
calcium
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
hydroxide dioxide
calcium + water
carbonate
The Limestone Cycle
These reactions all make up the
limestone cycle.
The limestone cycle
carbon
dioxide
limestone
heat
quicklime
limewater
more
water
water
Slaked lime
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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