Alternative Methods of Extracting Metals
Practise Alternative Methods of Extracting Metals for GCSE Chemistry with this free worksheet and full mark scheme — Higher-tier exam-style questions with worked answers for AQA, Edexcel and OCR. A Higher topic: phytomining and bioleaching extract copper from low-grade ores without the energy cost of traditional mining.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
This is a Higher tier only topic, so there's no Foundation paper — only the Higher worksheet and mark scheme below.
Topic overview
Copper ores are becoming scarce, so new methods have been developed to extract copper from low-grade ores. This is a Higher-only topic.
Phytomining uses plants to absorb metal compounds from the soil. The plants are harvested and burned, and the ash contains the metal compounds in a much higher concentration than the original ore.
Bioleaching uses bacteria to produce leachate solutions containing metal compounds. In both cases the copper is then obtained from the solution, either by displacement using scrap iron or by electrolysis. Both methods avoid the traditional processes of digging, moving and disposing of large amounts of rock.
Revision notes
Phytomining
Plants are grown on soil containing low-grade copper ore and absorb metal compounds as they grow.
The plants are harvested and burned. The ash produced contains the metal compounds in a much higher concentration than the original ore.
Bioleaching
Bacteria are used to produce leachate solutions that contain metal compounds.
The bacteria break down the ore, releasing the metal into solution. No heating is required, unlike traditional smelting.
Obtaining the metal
From either process, copper can be obtained from the solution by displacement using scrap iron, since iron is more reactive than copper.
Alternatively electrolysis can be used. Both new methods avoid digging, moving and disposing of large amounts of rock, so they cause less environmental damage.
Key points
- Copper ores are becoming scarce.
- Phytomining uses plants to absorb metal compounds.
- The plants are burned and the ash contains the metal.
- Bioleaching uses bacteria to produce leachate solutions.
- Copper is obtained by displacement with scrap iron.
- Both methods avoid moving large amounts of rock.
Worked examples
Example 1
Describe the process of phytomining. [3 marks]
Model answer
Plants are grown on soil containing low-grade copper ore and absorb metal compounds as they grow (1 mark). The plants are harvested and burned (1 mark). The ash contains the metal compounds in a much higher concentration than the original ore (1 mark).
Example 2
Explain how copper can be obtained from a leachate solution using scrap iron. [2 marks]
Model answer
Iron is more reactive than copper (1 mark), so it displaces copper from the solution, leaving copper metal (1 mark).
Example 3
Give one advantage of bioleaching over traditional mining. [2 marks]
Model answer
It avoids digging, moving and disposing of large amounts of rock (1 mark), so it causes less damage to the environment (1 mark).
Common mistakes
Saying phytomining extracts the metal directly.
The plants must be harvested and burned first, and the metal is obtained from the ash.
Confusing phytomining and bioleaching.
Phytomining uses plants; bioleaching uses bacteria.
Forgetting why scrap iron works.
Iron is more reactive than copper, so it displaces it.
Saying the new methods are faster.
They are generally slower; their advantage is environmental and using low-grade ores.
Exam tips
- Describe phytomining as a three-stage process.
- Explain displacement through relative reactivity.
- Give the environmental advantage when evaluating.
- Remember this is a Higher-only topic.
Key terms
- Phytomining
- Using plants to absorb metal compounds from soil.
- Bioleaching
- Using bacteria to produce metal-containing solutions.
- Leachate
- The solution containing dissolved metal compounds.
- Low-grade ore
- Ore containing only a small percentage of metal.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.