Where do metals come from?
They are found in the Earth's crust. We find most metals combined chemically with other chemical elements, often with oxygen. So the metal must be chemically separated from its compound before you can use it.
In some places, there's enough of a metal or metal compound in a rock to make it worth extracting the metal. We call this rock an ore. Ores are mined from the ground.
Some need to be concentrated before the metal is extracted and purified.
Whether it is worth extracting a particular metal depends on:
- How easy it is to extract from its ore
- How much metal the ore contains
A few metals, such as gold and silver, are so unreactive that they are found in the earth as metals themselves. We say they exist in their native state.
How do we extract metals?
The way in which we extract metals depends on its position on the reactivity series.
A more reactive metal will displace a less reactive metal from its compounds.
Extraction of Iron
Main reactions in a blast furnace..
Iron Oxide + Carbon --> Carbon Dioxide + Iron
Oxidation is when a substance gains oxygen or loses hydrogen.
Reduction is when a substance loses oxygen and gains hydrogen.
The carbon reduces iron oxide to form iron. This means carbon is the reducing agent for iron oxide (carbon is more reactive than iron as it can displace the oxygen from iron oxide to form iron).
Process in Blast Furnace
1. Iron Ore (mainly iron oxide), Coke (form of Carbon) and limestone (Calcium Carbonate) are the 3 solids in the top of the Blast Furnace
2. Hot air is blasted from the bottom of the Blast Furnace
3. The coke burns in the hot air
C + O --> CO2
4.At the temperature of the Blast Furnace (2000 degrees Celsius) other reactions happen
e.g. CO2 + C --> 2CO(toxic)
5. Carbon Monoxide reduces the iron oxide to form iron
Fe2O3 + 3CO --> 2Fe + 3CO2 molten iron runs out of bottom of the Blast Furnace
6. The limestone decomposes in the heat o the Blast Furnace.