Rocks
Most minerals come from rocks in the ground.
Rocks from which we can obtain a metal are known as ores
(eg Iron ore is a rock from which we can obtain iron).
Some rocks (like chalk or limestone) are slightly porous and full of tiny holes. These rocks can soak up water (or oil) and are called permeable.
Some rocks (like granite) are waterproof and are called impermeable.
Although there are over 100 elements, only about 9 of them appear in any quantity in the Earth’s crust.
IRON
Iron is obtained by heating the ore with coke.
Iron ore contains iron oxide and coke contains carbon and is made by heating coal.
The carbon in the coke pulls away the oxygen from the iron ore, leaving molten iron.
[Note: other elements, eg zinc, could be used to reduce the iron, but they are expensive and the iron is more difficult to purify after].
Word equation:
Iron oxide + carbon —-> Iron + carbon dioxide
Aluminium is too high in the activity series to be reduced by heating it with carbon.
Aluminium is obtained by a process called electrolysis, where an electric current is passed through the molten ore. This makes aluminium a lot more expensive than iron.
COPPER
Copper is low in the activity (and can be found native as the free metal) but is usually obtained by heating its ore with carbon. (See the page about using carbon in the activity series.
Copper is purified by electrolysis which makes it an expensive metal.
NEW WORDS:
Ore: A rock containing a metal. In most ores the metal is only present as a compound and needs to be refined in some way. Some ores containing unreactive metals, eg copper and gold, can contain the actual metal. A rock containing a metal. In most ores the metal is only present as a compound and needs to be refined in some way. Some ores containing unreactive metals, eg copper and gold, can contain the actual metal.
Electrolysis: The process of passing electricity through a liquid. This can cause the elements in the liquid to separate. Metals are formed on the cathode (negative electrode)
Properties of some common metals
| Metal | Advantage | Disadvantage | Use |
| Iron | Cheap, strong | Corrodes easily (rusts), heavy | Girders, bicycle frames |
| Aluminium | low density (light), can be hammered into thin sheets. | A little brittle, expensive | Aircraft bodies, kitchen foil, saucepans and many alloys |
| Copper | Malleable. Good conductor of heat and electricity. | Expensive, not very strong | Water pipes, electric wires. |
| Gold | Does not corrode. Attractive. Good conductor of electricity | Expensive, heavy | Electrical contacts.Jewellery and ornaments. |
Note: An ALLOY is a mixture containing more than one metal. Eg brass is an alloy of copper and zinc
