C 2 Limestone and building materials Flashcards
(14 cards)
What is limestone made of?
Limestone is mostly made of calcium carbonate (CaCO₃).
What happens when limestone is heated?
It decomposes to form calcium oxide (quicklime) and carbon dioxide.
CaCO₃ → heat → CaO + CO₂
What is the name of the reaction when a substance breaks down on heating?
Thermal decomposition.
What is calcium oxide used for?
It is used to neutralise acidic soils and in the production of cement.
What happens when you add water to calcium oxide?
It forms calcium hydroxide (slaked lime).
CaO + H₂O → Ca(OH)₂
What is calcium hydroxide used for?
It’s an alkali used to neutralise acids — for example, in treating acidic soil or lakes.
How can you test for carbon dioxide?
Bubble the gas through limewater; it will turn cloudy/milky.
What is limewater?
A solution of calcium hydroxide in water.
What is cement made from?
Cement is made by heating limestone with clay in a kiln.
What is mortar made from?
Cement + sand + water.
What is concrete made from?
Cement + sand + water + aggregate (e.g. gravel).
What are the advantages of using limestone to make building materials?
It’s widely available, relatively cheap, and strong when made into concrete.
What are the disadvantages of quarrying limestone?
Destroys habitats, creates noise and dust, uses large amounts of energy, can lead to visual pollution.
What are the environmental issues with heating limestone?
Releases CO₂ (a greenhouse gas) and uses fossil fuels.
