extractions and uses of metals

why is gold found as a raw metal?

gold is extremely unreactive and so doesn't react with things in the environment to from other compounds

How are most metals found in the Earth's crust?

as ores

when can a metal be extracted from an ore using carbon reduction

if the metal is less reactive than carbon so that the carbon can displace the metal from the ore

what method is used on metals that are more reactive than carbon

electrolysis

Why is electrolysis expensive?

A lot of energy is required to melt the ore and produce the required current.

extraction by heating with carbon (including iron)

iron oxide lose oxygen and is therefore reduced. the carbon gains oxygen and is therefore oxidised.
2Fe₂O₃(s) + 3C(s)-> 4Fe(l) + 3Co₂(g)
for iron this is carried out at high temperature in a blast furnace

Extraction by electrolysis (including aluminium):

metals that are more reactive than carbon are extracted using electrolysis of molten compounds
EXAMPLE
- aluminium is too reactive to be extracted using carbon
- aluminium is made by the electrolysis of a molten mixture of aluminium oxide and cyrolite using carbon as the anode

alternative methods

phytoextraction
- some plants absorb metal compounds through their roots and this concentrates these compounds
- the plants can be burned to produce an ash that contains these compounds
Bacteria extraction
-some bacteria absorb metal compounds
- produce solutions called leachates which contain the metals

properties and uses of aluminium

PROPERTIES:
- low density
- lightweight
- strong when alloyed
- resistant to corrosion → oxide layer
- good conductor

USES:
- airplaines
- foil
- electricity cables
- cooking equipment

properties and uses of copper

PROPERTIES:
- soft and easily bent
- good conductor of electricity
-does not react with water

USES:
- electrical wire
-plumbing

properties and uses of iron

Iron (blast furnace) is hard but too brittle for most uses and so is converted into steel
Raw iron is too soft for most uses

properties and uses of low carbon steel

0.25% carbon
easily shaped
mainly used for car bodies

properties and uses of high carbon steel

2.5% carbon
hard
used for cutting tools

properties and uses of stainless steel

chromium and nickel
resistant to corrosion
used for cutlery and sinks

what is an alloy

A mixture of two or more metals

which metals are usually turned into alloys

copper gold iron and aluminium

Why are alloys harder than pure metals?

the different sized atoms of the metals distort the layers in the structure, making it more difficult for them to slide over each other