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  • Created by: Cameron
  • Created on: 30-12-12 07:27

LIMESTONE & BUILDING MATERIALS

Limestone mostly made from  CALCIUM CARBONATE

The reaction when heat is applied to calcium carbonate:  (this is thermal decomposition)
calcium carbonate -->(heat)   calcium oxide + carbon dioxide 

The reaction when acid reacts with calcium carbonate:
calcium carbonate + sulfuric acid --> calcium sulphate + carbon dioxide + water
Calcium sulphate is a calcium salt. The salt depends on the acid used eg.
Hydrocloric acid would produce calcium cloride.  

Calcium Hydroxide is an alkali and can be used to neutralise acidic soil.
To form calcium hydroxide the reaction is:
calcium oxide + water --> calcium hydroxide

Calcium Hydroxide in a water solution is also known as limewater (test for carbon dioxide):
calcium hydroxide + carbon dioxide --> calcium carbonate + water
This forms a full cycle as you are left with the solid calcium carbonate (limestone)

CEMENT
powdered limestone + powdered clay
heated in a kiln

CONCRETE
cement + sand + agrigate
mixed

MORTAR (holds bricks together)
cement + sand + water
mixed 

Quarrying Limestone
Disadvantages:
- Destroys the habitats of animals and birds which may be endangered or become extinct,
  causes changes in the food chain. 
- The exposions caused by quarrying cause particulates and dust to pollute the air, this can   cause health problems such as asthma for workers and surrounding public. 

Advantages:
- Creates jobs and can help to boost the local economy
- Limestone is a vital component in everyday materials such as dyes, paints and medicines

ORES 
Ores contain enough metal to make extraction worthwhile. (profitability)

In many cases the ore is an oxide eg the main aluminium ore = bauxite
A metal can be extracted from its ore chemically - by reduction or electrolysis 

Reduction: Metaks higher than carbon in the reactivity series cannot be extracted by reduction using carbon. Reduction is done in a blast furnace eg. iron oxide --> iron 

Electrolysis: More expensive than reduction because it uses more energy as the metals are more reactive. eg aluminium, high temperature needed to melt aluminium oxide for extraction

Purifying through Electrolysis
Metals like copper can be extracted through reduction with carbon, hwever these metals come out as unpure. Electolysis can be used to purify it in order to make more conductive.

Copper-rich ores are running out: (new methods to extreact copper)
Bioleaching: uses bacteria to seperate copper from copper sulfide. 
Phytomining: grows plants in soil than contains copprt.

METALS
Recycling metals is important: 

1) Mining and extracting uses lots of energy, most comes from fossil fuels (running out)
2) Finite amount of each metal on earth, best to conserve these resources.
3) Reduces amount of landfill, pollutes surroundings.

Metlas are good structural materials, they tend to be durable and are good conductors.
Yet they are expensive to extract in some cases, can corrode and can suffer metal fatigue.
Copper - good conductor of electricity, doesnt react with water (wiring/plumbing)

Aluminium - corrosion resistant(forms thin layer of aluminium oxide), low density, more reactive than carbon so extracted…

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