extraction and uses of metals Flashcards
What is an ore?
a mineral that contains enough of a metal/compound to make it worthwhile extracting
What are the two main methods of extracting?
- electrolysis
- heating with reducing agent
Which metals in reactivity series require electrolysis?
all metals above carbon
Which metals in reactivity series require heating with a reducing agent?
zinc, iron, copper
which reducing agent is usually used?
carbon or carbon monoxide
how is silver/gold extracted?
they occur naturally
Which method of extraction is aluminium
electrolysis
What are the electrodes made out of?
graphite (carbon)
What is the electrolyte made out of?
solution of aluminium oxide dissolved in molten cryolite
What is the main ore of aluminium?
bauxite
Why is it dissolved in molten cryolite?
- bauxite has high melting point
- cryolite lower melting point
- cheaper and also better conductor of electricity than molten aluminium oxide
What is formed at cathode?
aluminium
What is formed at anode?
oxygen + 4 electrons
How is aluminium collected?
- melted
- collects at bottom
- tapped off
Why do electrodes need replacing?
- react with graphite to form carbon dioxide
- electrodes burn away
- regularly needs replacing
Raw materials needed for extraction of iron
- haematite (iron ore)
- coke (carbon)
- limestone (calcium carbonate
- air
Where are the raw materials inserted?
- hot air blasted at bottom
- rest are mixed and fed in at top
How is carbon monoxide formed?
- oxygen in air reacts with coke to form carbon dioxide
- carbon dioxide reacts with coke to form carbon monoxide
What is the purpose of the carbon monoxide?
- reducing agent for iron
What happens once the iron is reduced?
- melts
- collects at bottom of furnace where it is tapped off
What happens to the limestone?
calcium carbonate decomposes to form calcium oxide
What happens to the calcium oxide?
reacts with silicon dioxide (impurity of iron ore) to form calcium silicate
What happens to the silicate?
melts and collects as molten slag on top of molten iron
What is molten slag?
waste material produced in blast furnace during the production of iron
What is the cooled slag used for?
- road-building
- fertiliser
Properties of iron and aluminium
- dense and lustrous
- high melting ponts
- high tensile strength
- malleable
- good conductors of electricity and heat
what is wrought iron? give a property and uses
- pure iron
- malleable
- gates/ railings
what is cast iron? give a property and uses
- iron with 4% carbon and silicon (pig iron remelted under controlled conditions)
- brittle
- drainpipes, manholes, cooking pans
what is steel? give a property and uses
- alloy of iron, carbon and other metals
- hard but malleable(strong)
- car bodies, girders, bridges, ships, nails
what is stainless steel? give a property and uses
- alloy of iron and chromium and nickel (strong oxide layers protect iron from rust)
- resistant to corrosion
- cutlery, kitchen utensils, kitchen sinks
why is aluminium useful for food cans?
- resists corrosion
- non-toxic
why is aluminium useful for window frames?
resists corrosion
why is aluminium useful for aeroplane bodies/ bicycle frames?
- less dense than iron: weight of them
why is aluminium useful for power cables?
good conductor of electricity
why is aluminium useful for saucepans?
good conductor of heat
