1. GCSE 1.2 – Limestone Cycle
Limestone
Cycle!!!

2. Aims Limestone is mostly made of calcium carbonate
CaCO3 can decompose under heat to form calcium oxide and carbon dioxide
Calcium oxide can react with water to form calcium hydroxide
Calcium hydroxide can react with carbon dioxide to give calcium carbonate
The above reaction can be used as a test for CO2

3. What is Limestone?
Limestone is a sedimentary rock – built up over millions of years.
Cut into blocks it makes a pretty solid building material.

4. We are going to investigate some of the chemical reactions of limestone…
H2O
Add water
Thermal decomposition – ‘limelight’
Filter…
Blow through solution

5. CaCO3  CaO + CO2 CaO + H2O  Ca(OH)2 Ca(OH)2 + CO2  CaCO3 + H2O
calcium carbonate calcium oxide
CaO + H2O  Ca(OH)2
calcium oxide calcium hydroxide
Ca(OH)2 + CO2  CaCO3 + H2O
calcium hydroxide calcium carbonate
Are these equations balanced?

6. A reaction in which a compound is broken down using heat
Term
Definition
Limestone
A sedimentary rock mostly composed of calcium carbonate which can be used as a building material
Thermal decomposition
A reaction in which a compound is broken down using heat
Alkali
A substance which neutralises acids and is water soluble (as opposed to a base which is not water soluble but can neutralise acids)
Limewater
A solution of calcium hydroxide used to test for carbon dioxide, if the gas is present the limewater will turn cloudy when the gas is bubbled through it