AQA · GCSE · Combined Science

    Course version: 8464 · Version from Sept 2018

    Alternative methods of extracting metals (HT only): Students should be able to evaluate alternative biological methods of metal extraction, given appropriate information.

    Bioleaching and phytomining are biological alternatives to traditional metal extraction.

    • 3 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Bioleaching and phytomining are biological alternatives to traditional metal extraction. Bioleaching uses bacteria to break down low-grade ores, producing a leachate containing metal ions. Phytomining grows plants that absorb metal ions from soil; the plants are harvested and burned, and the ash is processed to recover the metal. To evaluate, compare these methods with conventional mining and smelting using supplied information: consider energy demand, cost, ore grade, land use, timescale, and environmental impact. For example, bioleaching can work on low-grade rock that traditional methods cannot economically process, but it is slow. A judgement must weigh benefits against drawbacks and be justified by the data given.

    What earns the marks

    • Identifies bioleaching as using bacteria to produce a leachate containing metal ions from low-grade ore.
    • Identifies phytomining as growing metal-absorbing plants, harvesting and burning them, then processing the ash.
    • Compares biological methods with traditional extraction in terms of energy use, cost, timescale, and environmental impact.
    • Uses the supplied information as evidence rather than relying only on general knowledge.
    • Reaches a justified conclusion about which method is more suitable, acknowledging trade-offs.

    Common mistakes and how to put them right

    • Describing bioleaching as melting ore.

      Put it right: Bioleaching uses bacteria to dissolve metal ions into solution, not heat.

    • Claiming phytomining involves genetically modifying plants to make metal.

      Put it right: Plants naturally absorb metal ions from soil, and the metal is recovered from the ash after burning.

    • Listing advantages and disadvantages without making a judgement.

      Put it right: An evaluation must reach a justified conclusion that weighs the evidence.

    Exam tips

    • Underline the command word evaluate and plan to include both sides plus a final justified judgement.
    • Use specific data from the supplied information, such as figures for energy, cost or land use, rather than vague statements.
    • Link each point to a named method and a named comparison, for example bioleaching versus smelting, to keep the evaluation focused.

    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 company is comparing two biological methods for extracting copper from low-grade ore. Method 1: Plants are grown on the ore, harvested, and burned to produce ash containing copper compounds. This takes 6 months per crop. Method 2: Bacteria break down the ore to produce a leachate solution of copper compounds. This takes several years but requires very little human intervention. Which statement correctly evaluates these methods based on this information?

    Listen

    Bioleaching and phytomining are biological alternatives to traditional metal extraction. Bioleaching uses bacteria to break down low-grade ores, producing a leachate containing metal ions. Phytomining grows plants that absorb metal ions from soil; the plants are harvested and burned, and the ash is processed to recover the metal. To evaluate, compare these methods with conventional mining and smelting using supplied information: consider energy demand, cost, ore grade, land use, timescale, and environmental impact. For example, bioleaching can work on low-grade rock that traditional methods cannot economically process, but it is slow. A judgement must weigh benefits against drawbacks and be justified by the data given. A strong answer earns marks for these points. Identifies bioleaching as using bacteria to produce a leachate containing metal ions from low-grade ore. Identifies phytomining as growing metal-absorbing plants, harvesting and burning them, then processing the ash. Compares biological methods with traditional extraction in terms of energy use, cost, timescale, and environmental impact. Uses the supplied information as evidence rather than relying only on general knowledge. A common slip: Describing bioleaching as melting ore. Instead, bioleaching uses bacteria to dissolve metal ions into solution, not heat. Exam tip: Underline the command word evaluate and plan to include both sides plus a final justified judgement.

    See it

    A top-down flowchart. A single node, low-grade ore or soil, splits into two routes. The first route goes to bioleaching, where bacteria break down ore, then to a leachate containing metal ions. The second route goes to phytomining, where plants absorb metal ions, then to harvesting and burning the plants, then to processing the ash to recover metal. Both the leachate node and the ash-processing node lead to a node for evaluating against traditional mining and smelting. That leads to a node for weighing energy, cost, ore grade, land use, timescale and environmental impact, which finally leads to a justified conclusion acknowledging trade-offs.
    It shows the two biological extraction routes, bioleaching and phytomining, leading into an evaluation against traditional methods and a justified 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.

    Environmental and economic evaluation

    Try answering aloud or in your head before turning the card.

    See every definition
    Bioleaching
    Uses bacteria to break down low-grade ores, producing a leachate containing metal ions.
    Phytomining
    Grows plants that absorb metal ions from soil; the plants are harvested and burned, and the ash is processed to recover the metal.
    Environmental and economic evaluation
    Weighs benefits against drawbacks, considering energy demand, cost, ore grade, land use, timescale and environmental impact, and is justified by the data given.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. A single node, low-grade ore or soil, splits into two routes. The first route goes to bioleaching, where bacteria break down ore, then to a leachate containing metal ions. The second route goes to phytomining, where plants absorb metal ions, then to harvesting and burning the plants, then to processing the ash to recover metal. Both the leachate node and the ash-processing node lead to a node for evaluating against traditional mining and smelting. That leads to a node for weighing energy, cost, ore grade, land use, timescale and environmental impact, which finally leads to a justified conclusion acknowledging trade-offs.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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