Extraction and uses of metals

What are most metals extracted from and how are unreactive metals found?

Most metals are found in the Earth’s crust combined with other elements. Such compounds are found in rocks called ore, rocks from which it is worthwhile to extract a metal.

A few very unreactive metals, such as gold, are found native which means they are found in the Earth’s crust as the uncombined element.

How is the method of extraction of a metal related to its position in the reactivity series?

Extraction of a metal from its ore typically involves removing oxygen from metal oxides.

 

If the ore contains a metal which is below carbon in the reactivity series then the metal is extracted by reaction with carbon in a displacement reaction.

If the ore contains a metal which is above carbon in the reactivity series then electrolysis (or reaction with a more reactive metal) is used to extract the metal.

Electrolysis is expensive due to the use of large amounts of energy to melt the compounds and to produce the electrical current (so you wouldn’t extract a metal using electrolysis if it could be done more cheaply using carbon)

What are the uses of aluminium, copper, iron and steel in terms of their properties?

• Aluminium – low density, corrosion-resistant, used for aircraft, trains, overhead power cables, saucepans and cooking foil

• Copper – soft and easily bent, good conductor of electricity, does not react with water, used for electrical wiring and plumbing

• Iron – from the blast furnace: hard, but too brittle for most uses, so converted to steel, pure iron: too soft for many uses

• Low carbon steel: 0.25% carbon, easily shaped, car body panels

• High carbon steel: 2.5% carbon, hard, cutting tools

• Stainless steel: chromium & nickel, resistant to corrosion, cutlery and sinks

What is an alloy?

• An alloy is a mixture of a metal and one or more elements, usually other metals or carbon

• Most metals in everyday uses are alloys. Pure copper, gold, iron and aluminium are all too soft for everyday uses and so are mixed with small amounts of similar metals to make them harder for everyday use.

• Gold in jewellery is usually an alloy with silver, copper and zinc

Why are alloys are harder than pure metals?

In a pure metal, the ions are all the same size and are in a regular arrangement of layers, meaning that they can slide over each other easily, making them soft. In an alloy, there are different sized ions,which disrupts the regular arrangement and prevents layers being able to slide over each other so easily.