Extraction of metals and reduction: interpret or evaluate specific metal extraction processes when given appropriate information

The idea

This statement asks you to work with information about a named extraction process, such as the blast furnace for iron, and explain what the data shows or make a judgement. Interpreting means extracting meaning: for example, reading a table of energy costs to decide which method is most viable. Evaluating means weighing evidence: for example, comparing the energy cost of electrolysis with the cost of heating a blast furnace. You should link each stage to reduction, which in this context means the loss of oxygen from the metal oxide, and to the reactivity series, which explains why some metals need electrolysis while others can be reduced by carbon. Practise converting unfamiliar contexts into these underlying principles.

What earns the marks

• Extract relevant values or labels from supplied data, such as temperature, energy demand, mass or percentage composition, and use them in the explanation.
• Explain how a metal is obtained from its ore by reduction, defining reduction as the loss of oxygen from the metal oxide.
• Compare two extraction routes using given evidence, for example energy demand, raw material cost, yield or carbon dioxide released.
• Reach a supported conclusion or judgement that follows from the data, stating whether a process is suitable and why.
• Relate the process to the reactivity series, explaining why a more reactive metal cannot be extracted by reduction with carbon and requires electrolysis.

Common mistakes and how to put them right

• Describing a process from memory without using the supplied information.

  Put it right by quoting or referring to specific data from the table, graph or diagram.

• Confusing reduction with oxidation in this context.

  Put it right by remembering that extracting a metal from its oxide involves the loss of oxygen, which is reduction.

• Writing a conclusion with no justification.

  Put it right by linking every judgement to a named piece of evidence, such as a higher energy cost or a lower yield.

Exam tips

• Read the whole resource, including axis labels, units and footnotes, before starting your answer.
• Use comparative language such as higher, lower, more energy-efficient or less polluting when evaluating two processes.