Revise: Properties of metalsExtraction of metals

Metal ores are naturally occurring rocks that contain metals or metal compounds in sufficient amounts to make it worthwhile extracting them. The method used to extract a given metal from its ore depends upon the reactivity of the metal and how stable the ore is.

In each case the metal ions in the compound gain electrons to form atoms of the metal element.

Extracting unreactive metals

Ores of unreactive metals only need to be heated to obtain the metal.

For example, black silver oxide can be heated to produce shiny silver metal and oyxgen gas.

Word equation

silver oxide → silver + oxygen

Chemical equation

2 Ag₂O(s) → 4 Ag(s) + 2 O₂(g)

Extracting reactive metals

Ores of reactive metals have to be heated with carbon or carbon monoxide in order to extract the metal.

Carbon is a non-metal but it is more reactive than some metals. This means that some metals can be extracted from their metal oxides using carbon.

This works for zinc, iron, tin, lead and copper. Copper is the least reactive of these five metals.

The general word equation for this reaction is:

metal oxide + carbon → metal + carbon dioxide

Extracting copper from copper oxide

To extract copper metal:

• Copper oxide powder is mixed with carbon powder.
• The mixture is heated strongly for a few minutes in a crucible. A lid is kept on the crucible to prevent the carbon from reacting with oxygen in the air, rather than with the copper oxide.
• The carbon dioxide formed in the reaction escapes into the air.
• The crucible is left to cool down.
• The mixture is tipped into cold water. Pieces of brown copper sink to the bottom, leaving unreacted powder suspended in the water.

These equations represent the reaction:

Word equation

copper oxide + carbon → copper + carbon dioxide

Chemical equation

2 CuO(s) + C(s) → 2 Cu(s) + CO₂(g)

Extracting very reactive metals

Ores of very reactive metals have to be melted and electrolysed with a direct current (DC) supply of electricity.

The positive metal ions are attracted to the negative electrode where they accept electrons.

This also works for less reactive metals, like copper. Watch this video to see how solid copper can be extracted from a solution using electrolysis.

The reaction in the video can be written as a word equation or chemical equation.

Word equation

copper chloride → copper + chlorine

Chemical equation

CuCl₂(aq) → Cu(s) + Cl₂(g)