Improving Processes & Products (OCR GCSE Combined Science A (Gateway): Chemistry): Flashcards
Exam code: J250
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- FrontExtracting Metals
What is a metal ore?
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What is a metal ore?
A metal ore is a rock that contains enough of a metal or metal compound to make extraction worthwhile.
True or False?
Unreactive metals like gold are often found as uncombined elements in the Earth's crust.
True.
Gold and platinum are found as native metals in the Earth's crust. They are unreactive and do not easily form compounds, so they are found uncombined as pure elements rather than as ores.
What determines whether a metal is extracted by carbon reduction or electrolysis?
The metal's position in the reactivity series determines the extraction method. Metals above carbon are extracted by electrolysis; metals below carbon can be reduced by heating with carbon.
In the extraction of iron, carbon monoxide reduces iron(III) oxide inside a ...........
In the extraction of iron, carbon monoxide reduces iron(III) oxide inside a blast furnace.
Why is limestone added to a blast furnace during iron extraction?
Limestone (calcium carbonate) is added to remove impurities such as silicon dioxide from the iron ore. It decomposes to calcium oxide, which reacts with the impurities to form molten slag.
What is electrolysis in the context of metal extraction?
Electrolysis is the process of using electrical energy to decompose a molten or dissolved ionic compound, used to extract metals that are too reactive to be reduced by carbon.
True or False?
Aluminium oxide is dissolved in water before electrolysis to extract aluminium.
False.
Aluminium oxide is dissolved in molten cryolite, not water. This lowers the melting point of the mixture, reducing the energy needed.
Why do the graphite anodes in aluminium electrolysis need to be replaced regularly?
The graphite anodes react with the oxygen produced at the anode to form carbon dioxide, gradually burning them away. This means they must be replaced regularly.
During electrolysis of aluminium oxide, aluminium ions are reduced at the ...........
During electrolysis of aluminium oxide, aluminium ions are reduced at the cathode.
Why is extracting aluminium by electrolysis more expensive than extracting iron by carbon reduction?
Extracting aluminium requires large amounts of electricity, which is costly. Electrolysis is needed because aluminium is too reactive to be reduced by carbon.
What is phytomining?
Phytomining is a process in which plants absorb metal ions through their roots, concentrate them in their shoots and leaves, and the harvested plant material is burned to produce ash from which metals can be extracted.
True or False?
(Higher Tier Only) Biological extraction methods such as phytomining and bioleaching are used for high-grade ores.
False.
Biological methods are developed for low-grade ores, where the metal content is too low to make traditional mining economically worthwhile.
(Higher Tier Only) What is the leachate produced during bioleaching?
The leachate is an acidic solution containing metal ions, produced when bacteria break down metal sulfide ores. The metal ions can then be extracted by displacement or electrolysis.
(Higher Tier Only) In phytomining, the harvested plant material is .......... to produce ash that contains metal compounds.
(Higher Tier Only) In phytomining, the harvested plant material is burned to produce ash that contains metal compounds.
(Higher Tier Only) Give one environmental advantage of biological extraction over traditional mining.
Biological extraction methods such as phytomining and bioleaching cause less damage to the landscape than traditional open-cast mining. They do not require large-scale excavation, reducing habitat destruction, noise pollution, and dust.
True or False?
(Higher Tier Only) Bioleaching uses bacteria to extract metals from ores.
True.
Bioleaching uses bacteria to extract metals from low-grade ores. The bacteria oxidise the metal compounds in the ore, producing a leachate solution containing metal ions that can be processed to obtain the metal.
(Higher Tier Only) Why are biological extraction methods considered slow compared to traditional methods?
Biological methods rely on living organisms — bacteria (bioleaching) or plants (phytomining) — which grow and process ores at natural rates. These biological processes take much longer than heating ores in a furnace, making them slower than traditional extraction methods.
(Higher Tier Only) After bioleaching, copper ions in the leachate can be recovered by .......... or .......... .
(Higher Tier Only) After bioleaching, copper ions in the leachate can be recovered by displacement or electrolysis.
What is a life cycle assessment (LCA)?
A life cycle assessment (LCA) is an analysis of the overall environmental impact of a product throughout its entire lifetime, from obtaining raw materials to disposal.
What are the four stages of a life cycle assessment?
A life cycle assessment (LCA) considers four stages: Raw materials extraction, Manufacture, Usage, and Disposal. Each stage is evaluated for its environmental impact, including energy use, resource consumption, and waste produced.
True or False?
Life cycle assessments are always completely objective.
False.
LCAs can be biased because it is difficult to quantify every stage precisely. The way data is selected and weighted can influence the conclusions.
Obtaining raw materials can damage the environment through .......... or deforestation.
Obtaining raw materials can damage the environment through mining or deforestation.
Give two environmental impacts associated with the disposal stage of an LCA.
Two environmental impacts from disposal are:
Using up space at landfill sites
Whether the product or its parts can be recycled rather than discarded
Why is it rare for a product to have zero environmental impact in an LCA?
Every stage of a product's life cycle — extracting raw materials, manufacturing, transporting, using, and disposing — requires energy and resources, and produces waste or emissions. It is extremely difficult to reduce the impact at every single stage to zero.
True or False?
The manufacturing stage of an LCA can include the environmental impact of transporting goods.
True.
Manufacturing processes include the use of fossil-fuelled machines for production and transport, both of which contribute to environmental impact.
LCAs often require a compromise between .......... impact and .......... factors.
LCAs often require a compromise between environmental impact and economical factors.
Give three benefits of recycling materials.
Three benefits of recycling are:
Conserves limited raw materials
Reduces harmful substances released into the environment
Reduces the amount of waste sent to landfill
True or False?
Glass bottles can be reused simply by washing and sterilising them.
True.
Glass bottles are reusable because they can be washed and sterilised without degrading. This makes them more sustainable than single-use plastic bottles over multiple uses, as fewer resources are needed per use.
To recycle metals, they are first crushed into smaller pieces, then .......... and recast into new shapes.
To recycle metals, they are first crushed into smaller pieces, then melted and recast into new shapes.
What are finite resources in the context of materials?
Finite resources are natural materials such as metal ores and crude oil that exist in limited quantities and cannot be replaced once used up.
Why must glass be separated by colour before recycling?
Glass must be separated by colour before recycling because mixing different coloured glass produces a discoloured product of lower quality. Separating by colour (clear, green, brown) ensures the recycled glass can be used to make new products of the same colour and quality.
True or False?
Recycled products always have the same quality as products made from new materials.
False.
Recycled products do not always have the same quality as those made from new materials. For example, recycled paper is often lower quality, and recycled plastics may have reduced strength or flexibility compared to virgin materials.
Give two factors that affect whether a material should be recycled.
Two factors affecting recycling decisions are:
How easy it is to collect and sort the waste
The cost of recycling compared to incineration or landfill
Recycling still has environmental costs because the .......... and transport of waste materials requires energy and fuel.
Recycling still has environmental costs because the collection and transport of waste materials requires energy and fuel.
Why can iron and steel waste be recycled together in a blast furnace?
Iron and steel can be recycled together because steel is an alloy of iron. In a blast furnace, both are melted down together. The scrap steel and iron are combined and reprocessed, as they share the same base metal and can be purified in the same process.
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