AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Students should be able to evaluate alternative biological methods of…
Full specification wording
Alternative methods of extracting metals (HT only): Students should be able to evaluate alternative biological methods of metal extraction, given appropriate information.
Biological methods use living organisms to extract metals from low-grade ores or waste.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 8 of 8
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Biological methods use living organisms to extract metals from low-grade ores or waste. In bioleaching, bacteria obtain energy by breaking down metal sulfide ores, producing a solution containing metal ions that can be processed to obtain the metal. In phytomining, plants absorb metal ions from the soil through their roots; the plants are harvested and burned, and the ash contains the metal compound, which is then processed. To evaluate these methods you must weigh advantages against disadvantages using the information given. Advantages can include working on low-grade ores, reduced need for high temperatures, and less landscape disruption than open-cast mining. Disadvantages can include slow rates, the need for large areas of land, and the energy or chemical processing still required afterwards. A judgement must be based on the evidence provided, not on a general preference.
What earns the marks
- Bioleaching uses bacteria to break down metal sulfide ores and release metal ions into solution.
- Phytomining uses plants to absorb metal ions from the soil; the plants are harvested and burned, and the ash is processed to obtain the metal.
- Evaluation requires identifying advantages such as use on low-grade ores and disadvantages such as slow rates or large land use.
- A justified conclusion must refer to the information supplied and weigh the benefits against the drawbacks.
- Biological methods still produce a metal compound that needs further processing to obtain the metal.
- Comparisons with traditional methods should consider energy use, cost, environmental impact and rate of extraction.
Common mistakes and how to put them right
Describing bioleaching or phytomining without making a judgement.
Put it right: Evaluation requires a conclusion that weighs advantages against disadvantages.
Claiming biological methods produce pure metal directly.
Put it right: They produce a solution or ash containing a metal compound that must be processed further.
Ignoring the information provided and writing a general answer about recycling.
Put it right: Base the evaluation on the data or details given in the question.
Exam tips
- Use the phrase 'however' to balance each advantage with a disadvantage before reaching a conclusion.
- Refer explicitly to figures or details from the supplied information to support each point.
- Finish with a clear overall judgement that answers the question directly.
Try the lesson
The start of the Alternative methods of extracting metals (HT only): Students should be able to evaluate alternative biological methods of metal extraction, given appropriate information. lesson, made from checked teaching notes for this specification point.
Have a go first
A mining company is considering using phytomining instead of traditional mining to extract copper from a low-grade ore. Phytomining involves growing plants on the ore, burning them, and extracting copper from the ash. Traditional mining involves digging up high-grade ore and smelting it. Which statement is a valid evaluation of choosing phytomining?
Listen
Biological methods use living organisms to extract metals from low-grade ores or waste. In bioleaching, bacteria obtain energy by breaking down metal sulfide ores, producing a solution containing metal ions that can be processed to obtain the metal. In phytomining, plants absorb metal ions from the soil through their roots; the plants are harvested and burned, and the ash contains the metal compound, which is then processed. To evaluate these methods you must weigh advantages against disadvantages using the information given. Advantages can include working on low-grade ores, reduced need for high temperatures, and less landscape disruption than open-cast mining. Disadvantages can include slow rates, the need for large areas of land, and the energy or chemical processing still required afterwards. A judgement must be based on the evidence provided, not on a general preference. A strong answer earns marks for these points. Bioleaching uses bacteria to break down metal sulfide ores and release metal ions into solution. Phytomining uses plants to absorb metal ions from the soil; the plants are harvested and burned, and the ash is processed to obtain the metal. Evaluation requires identifying advantages such as use on low-grade ores and disadvantages such as slow rates or large land use. A justified conclusion must refer to the information supplied and weigh the benefits against the drawbacks. A common slip: Describing bioleaching or phytomining without making a judgement. Instead, evaluation requires a conclusion that weighs advantages against disadvantages. Exam tip: Use the phrase 'however' to balance each advantage with a disadvantage before reaching a conclusion.
Key words
Say what each word means before you turn the card.
Bioleaching
Try answering aloud or in your head before turning the card.
Phytomining
Try answering aloud or in your head before turning the card.
Evaluating evidence and reaching justified conclusions
Try answering aloud or in your head before turning the card.
Environmental and economic trade-offs in extraction
Try answering aloud or in your head before turning the card.
See every definition
- Bioleaching
- Bacteria obtain energy by breaking down metal sulfide ores, producing a solution containing metal ions that can be processed to obtain the metal.
- Phytomining
- Plants absorb metal ions from the soil through their roots, are harvested and burned, and the ash contains the metal compound, which is then processed.
- Evaluating evidence and reaching justified conclusions
- Weighing advantages against disadvantages using the information given, with a judgement based on the evidence provided, not on a general preference.
- Environmental and economic trade-offs in extraction
- Weighing advantages such as working on low-grade ores and less landscape disruption against disadvantages such as slow rates and the need for large areas of land.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Alternative methods of extracting metals (HT only): Students should be able to evaluate alternative biological methods of metal extraction, given appropriate information.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge