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Year 11
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Higher

Electrolysis: extracting aluminium

I can explain why electrolysis is required for the extraction of aluminium from its ore and describe the process.

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New
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Year 11
OCR
Higher

Electrolysis: extracting aluminium

I can explain why electrolysis is required for the extraction of aluminium from its ore and describe the process.

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Lesson details

Key learning points

  1. Aluminium is above carbon in the reactivity series and can therefore not be extracted with carbon.
  2. Impurities are removed from the bauxite ore at the start.
  3. Cryolite acts as a solvent and allows the electrolysis to take place at a lower temperature.
  4. Carbon electrodes need to be continuously replaced as they react with oxygen as it is produced, forming carbon dioxide.
  5. Electrolysis is an expensive process as it requires large amounts of energy.

Keywords

  • Aluminium oxide - a compound consisting of two aluminum atoms and three oxygen atoms

  • Bauxite - a sedimentary rock with a high aluminium content

  • Cryolite - a compound used in the smelting of aluminium to lower the melting point

Common misconception

Understanding why carbon dioxide is produced at the anode, when there is no carbon in aluminium oxide.

Remind students of previous knowledge about combustion reactions. Help them to apply this knowledge to this new situation in the electrolysis cell.

Show a video of the industrial extraction of aluminium from bauxite.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
What is the reactivity series of metals?
a list of metals ranked by their melting points
Correct answer: a list of metals ranked by their reactivity with water, acids, and oxygen
a table showing how metals combine to form compounds
a list of elements ranked by their atomic numbers
Q2.
What does the reactivity series of metals help determine?
Correct answer: the method of extraction.
the boiling points of metals.
the abundance of metals.
Q3.
What is electrolysis used for in chemistry?
to combine elements into compounds
to measure the reactivity of elements
Correct answer: to split compounds into their elements using electricity
Q4.
What is a common feature of ores?
They all contain carbon.
They are all shiny.
Correct answer: They contain metals that can be extracted.
They are always found in pure form.
Q5.
What is required for industrial processes?
high temperatures and pressures
Correct answer: large amounts of raw materials and energy
pure elements in their natural form
low costs and simple machinery
Q6.
What type of rock is bauxite?
Correct answer: sedimentary rock
igneous rock
metamorphic rock
volcanic rock

Exit quiz

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6 Questions

Q1.
Why can't aluminium be extracted using carbon?
Aluminium and carbon form a compound.
Correct answer: Aluminium is above carbon in the reactivity series.
Aluminium is less reactive than carbon.
Q2.
What is the role of cryolite in aluminium extraction?
to extract aluminium directly
to increase the melting point of aluminium oxide
Correct answer: to lower the melting point of aluminium oxide
Q3.
What ions are present in molten aluminium oxide (Al₂O₃)?
Correct answer: Al³⁺ and O²⁻
Al⁺ and O⁻
Al²⁺ and O⁻
Al⁴⁺ and O²⁻
Q4.
During electrolysis, where do aluminium ions move?
to the anode
Correct answer: to the cathode
to the electrolyte
Q5.
Why does the anode need to be replaced during electrolysis?
It dissolves in aluminium.
It reacts with cryolite.
Correct answer: It reacts with oxygen to form carbon dioxide.
It stop conducting electricity.
Q6.
Why is aluminium recycling economically beneficial?
It produces more aluminium.
It requires more carbon electrodes.
Correct answer: It uses less energy than extracting new aluminium.