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Extraction of Metals

Most metals are only found as compounds because the metal has reacted with other elements in the past. Because of this, the metal has to be extracted from the ore (rock) where the metal compound is found.

Carbon - why

Carbon - why

  • Metals that are less reactive than carbon can be extracted from their oxides (compounds with oxygen) by reducing with carbon.
  • Carbon is used because it is cheap and abundant.
Carbon - how

Carbon - how

  • In the reduction, the metal oxide loses oxygen to form a pure metal.
  • Reduction with carbon normally involves heating the metal oxide in the presence of the carbon, which is often used in the form of coal.

Electrolysis - Extracting Metals

Electrolysis is used to extract reactive metals from molten ores (melted materials containing metals). It is used to extract metals such as aluminium, which are more reactive than carbon.

Process

Process

  • Powdered aluminium ore (Al2O3) is first mixed with another aluminium salt called cryolite.
  • This mixture has a lower melting point than pure Al2O3. This makes it cheaper as less energy is needed to melt the powder.
  • Once molten, a large voltage is applied.
At the cathode (negative electrode)

At the cathode (negative electrode)

  • The aluminium is formed at the cathode.
At the anode (positive electrode)

At the anode (positive electrode)

  • Carbon dioxide is formed at the anode.
  • The anode is usually made of carbon because it is a good conductor and is cheap.
Disadvantages

Disadvantages

  • Lots of energy is needed to:
    • Melt the solid ionic compound to allow the ions to flow.
    • To produce the electrical current.
  • All this energy costs money, and a lot of it!
Jump to other topics
1

Principles of Science I

1.1

Structure & Bonding

1.2

Properties of Substances

1.3

Cell Structure & Function

1.4

Cell Specialisation

1.5

Tissue Structure & Function

1.6

Working with Waves

1.7

Waves in Communication

2

Practical Scientific Procedures and Techniques

3

Science Investigation Skills

4

Principles of Science II

4.1

Extracting Elements

4.2

Relating Properties to use of Substances

4.3

Organic Chemistry

4.4

Energy Changes in Industry

4.5

The Circulatory System

4.6

Ventilation & Gas Exchange

4.7

Urinary System

4.8

Cell Transport

4.9

Thermal Physics

4.10

Materials

4.11

Fluids

5

Contemporary Issues in Science

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