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GCSE Chemistry · GCSEChapter 19 · Resources, metals, life cycle assessment and recycling
GCSE · Chapter 19

Resources, metals, life cycle assessment and recycling

By the end of this chapter you will be able to

  • Classify resources as finite or renewable, and explain sustainability
  • Choose an extraction method for a metal from its reactivity
  • Name the stages of a life cycle assessment and compare two products
  • Give benefits and costs of recycling, and explain why recycling aluminium is efficient
  • [H] Explain why fertilisers are needed, and link the Haber process to ammonia production

You should already know

  • Reactivity series and displacement (Chapter 3)
  • Electrolysis of aluminium oxide (Chapter 11)
  • Haber process and conditions (Chapter 14)

Where this leads

  • Synthesis of the wider chemical industry (A-level and IGCSE follow-on)
  • Sustainability in every topic

GCSE Chemistry. Content follows the GCSE (9-1) subject content for England (Edexcel and AQA). Content references: Describe finite and renewable resources, and the sustainable use of resources, Describe how metals are extracted from their ores, including reduction with carbon and electrolysis, Describe life cycle assessment (LCA) and compare two products using LCA data, Discuss the costs and benefits of recycling metals, glass, plastics and paper, [H] Describe the Haber process and the fertilisers (nitrogen, phosphorus and potassium) made from it.

Exercise P  Do you remember?

1
FWhich metal is extracted by electrolysis of its molten oxide? Write the name.
2
FWhich gas is produced at the anode when molten sodium chloride is electrolysed? Write the name.
3
FIs crude oil a finite or renewable resource? Write the word.
4
FWhat is the Ar of iron? Write the number. (Use the periodic table value of 56.)
5
FWhat is 2 x 4 + 2 x 6? Write the number.
19.1

Finite and renewable resources

GCSE
Describe finite and renewable resources, and the sustainable use of resources
Video lesson: Finite and renewable resourcesComing soon
Context. A council asks whether it should keep using a mine or switch to a wind farm. “Which resource will last?” asks a councillor. Finite resources, such as metal ores, will run out; renewable resources can be replaced, if they are used sustainably.

A finite resource is one that cannot be replaced at the rate we use it, such as fossil fuels and metal ores. A renewable resource can be replaced, such as wood from managed forests, crops and energy from wind, sunlight and water. A sustainable use meets today’s needs without damaging the chance of future generations to meet theirs.

ResourceTypeNotes
crude oil, natural gas, coalfinite (non-renewable)formed over millions of years; used faster than formed
metal ores (for example iron ore, copper ore)finitewill run out, and lower-grade ores need more energy
phosphate rockfinitesource of phosphorus for fertilisers
wood and cropsrenewablecan be grown again if managed sustainably
wind, sunlight and water powerrenewabledo not run out, and produce little pollution in use
Finite and renewable resources

Key ideas

  • Finite: fossil fuels and metal ores; they will run out.
  • Renewable: crops, wood and energy from wind, sunlight and water.
  • Sustainable use: meets the needs of today without harming the future.
  • Using less, recycling and using renewable sources all help sustainability.
Worked example 19.1.1
Give one finite resource used to make fuel. Write the name.

Method. Recall a finite fuel.

  1. Recall. Crude oil is a finite resource used for fuel.
    crude oil
  2. Check. Fossil fuels form over millions of years, so they cannot be replaced quickly.
    fossil fuels
  3. Write the answer.
    crude oil

Check. Natural gas and coal are other examples. ✓

Worked example 19.1.2
Which type of resource is wind energy? Write the word: finite or renewable.

Method. Think about whether wind can be replaced.

  1. Look. Wind is replaced naturally and will not run out.
    replaced
  2. Decide. So wind is a renewable resource.
    renewable
  3. Write the answer.
    renewable

Check. Wind power produces little pollution in use. ✓

Worked example 19.1.3
What does sustainable use of a resource mean? Write the words.

Method. Recall the definition.

  1. Recall. Sustainable use meets today’s needs without harming future needs.
    meets today’s needs
  2. Check. So resources are used at a rate they can be replaced, or conserved.
    replaced
  3. Write the answer.
    meeting current needs without harming future generations

Check. Sustainability is a key idea. ✓

Watch out

Watch out: renewable does not always mean sustainable. Wood from a forest that is cut down faster than it is replanted is not sustainable.

Exam tip

Exam tip. Name the resource, say finite or renewable, and give one reason.

Exercise 19A  Finite and renewable resources

1
FIs coal a finite or renewable resource? Write the word.
2
FIs wood from a managed forest finite or renewable? Write the word.
3
FIs sunlight used for electricity finite or renewable? Write the word.
4
FName a finite metal resource. Write the name. Accept any metal ore, such as iron ore or copper ore.
5
FWhat does a sustainable resource use meet? Write the words.
6
FWhich is the more sustainable choice: a finite fuel or a renewable fuel? Write the word.
7
FGive one way to use resources more sustainably. Write the words. Accept recycling or using less.
8
RExplain why phosphate rock is a finite resource, in one sentence. Accept any sentence that says it forms over very long periods and cannot be replaced quickly.
9
RExplain why a renewable resource can still be used unsustainably, in one sentence. Accept any sentence that says it is used faster than it can be replaced.
19.2

Extracting metals from their ores

GCSE
Describe how metals are extracted from their ores, including reduction with carbon and electrolysis, [H] Explain the reduction of iron oxide by carbon monoxide
Video lesson: Extracting metals from their oresComing soon
Context. A pupil asks how iron is made from iron ore, which looks like a rust-coloured rock. “Why not just heat it?” asks the pupil. The metal must be separated from the oxygen in the ore, and the method depends on how reactive the metal is.

Metals are found as ores, which are rocks containing the metal compound. A metal less reactive than carbon can be extracted by reduction with carbon: the carbon removes the oxygen. Iron is extracted in a blast furnace from iron ore, coke (carbon) and limestone. A metal more reactive than carbon, such as aluminium, must be extracted by electrolysis of its molten oxide.

Bioleaching (bacteria) and phytomining (plants that absorb metal) are ideas for extracting metals from low-grade ores; they use less energy but are slow.

Blast furnace (simplified): reduction of iron ore with carbon monoxideiron ore + coke + limestone inhot air blown in at the bottommolten iron out at the bottomcarbon monoxide reduces the iron oxide:Fe<sub>2</sub>O<sub>3</sub> + 3CO -> 2Fe + 3CO<sub>2</sub>
The blast furnace: carbon monoxide reduces the iron oxide to iron
MetalMethod of extractionReason
ironreduction in a blast furnace with carbon (as carbon monoxide)iron is less reactive than carbon
copper (from copper oxide)reduction with carboncopper is less reactive than carbon
aluminiumelectrolysis of molten aluminium oxidealuminium is more reactive than carbon, so carbon cannot reduce it
Choosing an extraction method from the reactivity of the metal

[H] Higher tier only. In the blast furnace, coke (carbon) reacts with the hot air to make carbon monoxide, which reduces the iron oxide: Fe2O3 + 3CO -> 2Fe + 3CO2. The carbon monoxide takes the oxygen from the iron oxide, which is a reduction (loss of oxygen).

Key ideas

  • Metals less reactive than carbon are extracted by reduction with carbon.
  • Metals more reactive than carbon (such as aluminium) are extracted by electrolysis.
  • Iron: blast furnace, iron ore + coke + limestone.
  • Bioleaching and phytomining are low-energy but slow ideas for low-grade ores.
Worked example 19.2.1
Why is aluminium extracted by electrolysis rather than by heating with carbon? Write the words.

Method. Compare the reactivity with carbon.

  1. Look. Aluminium is more reactive than carbon.
    more reactive
  2. Conclude. So carbon cannot remove the oxygen from aluminium oxide; electrolysis is needed.
    electrolysis needed
  3. Write the answer.
    aluminium is more reactive than carbon, so carbon cannot reduce it

Check. Electricity supplies the electrons. ✓

Worked example 19.2.2
What does iron ore react with, in the blast furnace, to remove its oxygen? Write the name of the gas.

Method. Recall the reducing agent.

  1. Recall. Carbon monoxide reduces the iron oxide.
    carbon monoxide
  2. Check. Carbon monoxide is made from coke and hot air in the furnace.
    made from coke
  3. Write the answer.
    carbon monoxide

Check. It removes the oxygen from the iron oxide. ✓

Worked example 19.2.3
Name the process by which a metal oxide loses oxygen. Write the word.

Method. Recall the process.

  1. Recall. Losing oxygen is reduction.
    reduction
  2. Check. The metal oxide is reduced to the metal.
    reduced
  3. Write the answer.
    reduction

Check. Oxidation is gaining oxygen. ✓

Watch out

Watch out: a metal less reactive than carbon is extracted by reduction with carbon, but a metal more reactive than carbon needs electrolysis. Use the reactivity series to decide.

Exam tip

Exam tip. State the metal, its reactivity compared with carbon, and the method. The reason is the key mark.

Exercise 19B  Extracting metals from their ores

1
FWhat is an ore? Write the words.
2
FIn the blast furnace, what is the carbon source? Write the name.
3
FWhat is added to the blast furnace to remove impurities? Write the name.
4
FWhich metal is extracted by electrolysis of its molten oxide? Write the name.
5
FIs copper extracted by reduction with carbon? Write yes or no.
6
F[H] What is the carbon monoxide equation for reducing iron oxide, in the simplified form? Write the number in front of Fe.
7
PS[H] In Fe2O3 + 3CO -> 2Fe + 3CO2, how many oxygen atoms are on the left? Write the number.
8
RExplain why copper oxide can be reduced by carbon, but aluminium oxide cannot, in one sentence. Accept any sentence that says copper is less reactive than carbon, while aluminium is more reactive.
9
RGive one advantage and one disadvantage of phytomining, in one or two sentences. Accept any answer that gives low energy use as an advantage and slow extraction as a disadvantage.
10
R[H] Explain why reduction is a loss of oxygen, using the iron oxide example, in one sentence. Accept any sentence that says the iron oxide loses oxygen to become iron.
19.3

Life cycle assessment

GCSE
Describe life cycle assessment (LCA) and compare two products using LCA data
Video lesson: Life cycle assessmentComing soon
Context. Two shopping bags are compared: one made of paper and one of plastic. “Which is better for the environment?” asks a pupil. A life cycle assessment (LCA) looks at the whole life of each product, from raw materials to disposal, before a fair comparison is made.

A life cycle assessment studies the environmental impact of a product at each stage: raw materials (extraction), manufacture, use and disposal or recycling. The results are compared for each stage, using data such as energy, water, waste and emissions. A product with a lower overall impact is preferred, but the choice also depends on the purpose and the cost.

raw materialsmanufactureusedisposal or recyclingan LCA follows a product through all four stages
The four stages of a life cycle assessment

Key ideas

  • LCA stages: raw materials, manufacture, use, disposal or recycling.
  • LCA uses data (energy, water, waste, emissions) to compare products fairly.
  • The product with the lowest total impact is generally preferred.
  • An LCA can show where in the life cycle the impact is largest.
Worked example 19.3.1
Name the four stages of a life cycle assessment. Write the four words in order.

Method. Recall the stages in order.

  1. Recall. Raw materials, manufacture, use, and disposal or recycling.
    four stages
  2. Check. These follow the product from start to end of life.
    start to end
  3. Write the answer.
    raw materials, manufacture, use, disposal or recycling

Check. Each stage is compared. ✓

Worked example 19.3.2
In an LCA, what is the first stage? Write the words.

Method. Think about the start of the life cycle.

  1. Look. The first stage is where the materials come from.
    come from
  2. Decide. So the first stage is raw materials.
    raw materials
  3. Write the answer.
    raw materials

Check. It includes extraction of ores and crops. ✓

Worked example 19.3.3
Why does an LCA consider the use and disposal stages as well as manufacture? Write one reason.

Method. Think about the whole life.

  1. Look. Some products use a lot of energy or water during use.
    use energy
  2. Conclude. Disposal can also cause pollution or waste.
    pollution
  3. Write the answer.
    a product can have a large impact during use or at disposal, not only in manufacture

Check. The whole life is compared. ✓

Watch out

Watch out: an LCA compares the whole life, not one stage. A product that is cheap to make may have a high impact when it is used or thrown away.

Exam tip

Exam tip. In a comparison, name a stage, say which product has the higher impact there, and give the overall conclusion.

Exercise 19C  Life cycle assessment

1
FWhat does LCA stand for? Write the words.
2
FName the stage in an LCA when the product is thrown away or recycled. Write the words.
3
FIn which stage of an LCA are the materials taken from the ground? Write the words.
4
FWhich stage of an LCA covers the making of the product? Write the word.
5
FHow many stages are in a standard LCA? Write the number.
6
PSAn LCA shows a plastic bag uses less energy to make than a paper bag, but it does not biodegrade. Which factor would a fair LCA include? Write the word: disposal.
7
PSTwo products are compared: product A has high energy use in manufacture, and product B has high impact in use. Which stage differs most? Write the stage name.
8
RExplain why a life cycle assessment is useful for choosing a product, in one sentence. Accept any sentence that says it shows the overall environmental impact across the whole life of the product.
9
RExplain why an LCA is not always enough to decide between two products, in one sentence. Accept any sentence that says cost, purpose and performance must also be considered.
19.4

Recycling

GCSE
Discuss the costs and benefits of recycling metals, glass, plastics and paper
Video lesson: RecyclingComing soon
Context. A school sets up bins for cans, glass, plastic and paper. “Is it worth the trouble?” asks a pupil. Recycling saves raw materials and energy, but it has costs in collection, sorting and transport.

Recycling conserves resources and reduces waste. Recycling metals such as aluminium saves ore and a great deal of the energy needed to extract the metal from its ore. Recycling glass saves raw materials; plastics save crude oil, but need careful sorting; and paper saves trees and water, though the fibres weaken each time it is recycled.

MaterialBenefitCost or difficulty
metals (aluminium, steel, copper)saves ore and much of the energy of extractioncollection, sorting and transport
glasssaves raw materials; can be melted and reusedneeds sorting by colour
plasticssaves crude oil and reduces landfillmany types must be sorted; contamination
papersaves trees and waterfibres weaken each time it is recycled
Benefits and costs of recycling different materials

Key ideas

  • Recycling saves raw materials and energy, and reduces landfill.
  • Metals: saves ore and energy; aluminium recycling uses much less energy than extraction.
  • Costs: collection, sorting, transport and contamination.
  • Paper fibres weaken, so paper can only be recycled a limited number of times.
Worked example 19.4.1
Why is recycling aluminium more efficient than making it from its ore? Write one reason.

Method. Compare the energy needed.

  1. Look. Extracting aluminium from its ore needs a very large amount of energy for electrolysis.
    large energy
  2. Conclude. Recycling aluminium uses far less energy, as it is melted rather than extracted.
    far less energy
  3. Write the answer.
    it uses much less energy, because the metal is melted rather than extracted

Check. It also saves the ore. ✓

Worked example 19.4.2
Give one cost of recycling. Write the words.

Method. Think about the process.

  1. Look. Recycling needs materials to be collected and sorted.
    collected and sorted
  2. Conclude. This costs time, money and transport.
    costs money
  3. Write the answer.
    collection, sorting and transport cost time and money

Check. Contamination also makes recycling harder. ✓

Worked example 19.4.3
Why can paper be recycled only a limited number of times? Write the words.

Method. Think about the fibres.

  1. Look. Each recycling process breaks and shortens the paper fibres.
    shortens
  2. Conclude. So the paper becomes weaker and must eventually be replaced with new fibres.
    weaker
  3. Write the answer.
    the fibres become shorter and weaker each time

Check. New fibres are needed. ✓

Watch out

Watch out: recycling is not always better. Compare the energy and the cost of the recycling process with the energy and cost of making the material new.

Exam tip

Exam tip. Give a benefit and a cost for recycling, and a specific reason for each.

Exercise 19D  Recycling

1
FName one metal that is recycled to save energy. Write the name.
2
FWhat resource is saved by recycling plastics? Write the words.
3
FWhat resource is saved by recycling paper? Write the words. Accept trees or wood.
4
FWhat is the main benefit of recycling glass? Write the words.
5
FName one cost of recycling. Write the words.
6
FWhy must plastics be sorted before recycling? Write one reason.
7
FWhy does paper fibre weaken when it is recycled? Write the words.
8
PSIs recycling always better than making a new product? Write yes or no.
9
RExplain why recycling aluminium saves energy, in one sentence. Accept any sentence that says the metal is melted rather than extracted from its ore by electrolysis.
10
REvaluate recycling as a way of conserving resources, in two sentences. Accept any answer that gives a benefit (resources saved) and a cost (collection, sorting and transport), with a balanced view.
19.5

Fertilisers and the Haber process [H]

GCSE
[H] Describe the Haber process and the fertilisers (nitrogen, phosphorus and potassium) made from it
Video lesson: Fertilisers and the Haber process [H]Coming soon
Context. A farmer adds fertiliser to a field of wheat. “Why do plants need more than sunlight and water?” asks a pupil. Plants need nitrogen, phosphorus and potassium from the soil, and fertilisers supply them when the soil runs low.

[H] Higher tier only. Ammonia made by the Haber process (N2 + 3H2 ⇌ 2NH3) is used to make nitrogen fertilisers, such as ammonium nitrate. Phosphate rock is mined and treated to make phosphate fertilisers, and potassium compounds supply potassium. Fertilisers are often labelled N, P and K.

NutrientElementWhy plants need it
nitrogen (N)Nto make proteins and chlorophyll
phosphorus (P)Pfor growth and roots
potassium (K)Kfor healthy plant cells and disease resistance
The main plant nutrients (N, P and K)

Key ideas

  • Plants need nitrogen, phosphorus and potassium (N, P, K).
  • [H] The Haber process makes ammonia, which is used to make nitrogen fertilisers.
  • [H] Phosphate rock is a finite resource used for phosphate fertilisers.
  • Fertilisers help crops grow, but excess can run off into water and cause problems.
Worked example 19.5.1
[H] Which element is supplied by a nitrogen fertiliser? Write the symbol.

Method. Recall the nutrient.

  1. Recall. Nitrogen fertilisers supply nitrogen.
    nitrogen
  2. Symbol. The symbol for nitrogen is N.
    N
  3. Write the answer.
    N

Check. The ammonia comes from the Haber process. ✓

Worked example 19.5.2
[H] What is made in the Haber process that is used to make nitrogen fertilisers? Write the name.

Method. Recall the product.

  1. Recall. The Haber process makes ammonia.
    ammonia
  2. Decide. Ammonia is used to make nitrogen fertilisers.
    ammonia
  3. Write the answer.
    ammonia

Check. Ammonium nitrate is one such fertiliser. ✓

Worked example 19.5.3
[H] Name the finite resource that is used to make phosphate fertilisers. Write the name.

Method. Recall the resource.

  1. Recall. Phosphate rock is mined to make phosphate fertilisers.
    phosphate rock
  2. Check. Phosphate rock is finite, so it cannot be replaced quickly.
    finite
  3. Write the answer.
    phosphate rock

Check. It is a source of phosphorus. ✓

Watch out

Watch out: fertilisers are not all the same. Each supplies a different nutrient, and the balance of N, P and K matters for healthy crops.

Exam tip

Exam tip. Name the nutrient, the plant need it meets, and where the fertiliser comes from.

Exercise 19E  Fertilisers and the Haber process [H]

1
F[H] What is the symbol for phosphorus? Write the symbol.
2
F[H] What is the symbol for potassium? Write the symbol.
3
F[H] Which element does the Haber process supply to crops, through fertilisers? Write the name.
4
F[H] Name the plant nutrient that is needed for healthy roots and growth, and is supplied by phosphate fertilisers. Write the name.
5
F[H] What does NPK stand for on a fertiliser label? Write the words.
6
PS[H] Why is ammonia made in the Haber process used for fertilisers? Write one reason.
7
R[H] Explain why a farmer uses fertilisers, in one sentence. Accept any sentence that says the soil may lack nutrients, so fertilisers replace them and help crops grow.
8
R[H] Explain why phosphate rock is a concern for the future, in one sentence. Accept any sentence that says it is a finite resource that will eventually run out.
9
R[H] Explain why excess fertiliser can cause problems in water, in one sentence. Accept any sentence that says the nutrients run off into rivers and lakes, causing algal growth.

Chapter summary

SkillMethod
Finite resourcesFossil fuels, metal ores, phosphate rock: they will run out.
Renewable resourcesWood, crops, wind, sunlight, water: replaced naturally, if used sustainably.
ExtractionLess reactive than carbon: reduction with carbon. More reactive: electrolysis.
Life cycle assessmentRaw materials, manufacture, use, disposal or recycling; compare with data.
RecyclingSaves resources and energy; costs in collection, sorting and transport.
[H] FertilisersHaber ammonia gives nitrogen fertiliser; NPK nutrients for crops.

Can you…?

  • I can classify resources as finite or renewable and explain sustainability
  • I can choose an extraction method for a metal from its reactivity
  • I can describe the stages of a life cycle assessment and compare products
  • I can give the benefits and costs of recycling different materials
  • [H] I can explain fertilisers and the link to the Haber process

Key terms

finite resource
a resource that cannot be replaced at the rate it is used
renewable resource
a resource that can be replaced naturally
sustainable
meeting the needs of today without harming future generations
ore
a rock that contains a metal compound in enough quantity to extract the metal
life cycle assessment
a study of the environmental impact of a product at each stage of its life
bioleaching
using bacteria to extract metals from low-grade ores
phytomining
using plants that absorb metals to extract them from low-grade ores
fertiliser
a substance added to soil to supply plant nutrients such as nitrogen, phosphorus and potassium

Exercise 19Z  Check-up

1
Is wind energy a finite or renewable resource? Write the word.
2
Which metal is extracted by electrolysis? Write the name.
3
Which gas reduces iron oxide in the blast furnace? Write the name.
4
Name the first stage of a life cycle assessment. Write the words.
5
Name a material for which recycling saves trees. Write the name.
6
Why is recycling aluminium efficient? Write the words.
7
[H] What is the name of the fertiliser element supplied by ammonia? Write the name.
8
Explain why a metal more reactive than carbon cannot be extracted by reduction with carbon, in one sentence. Accept any sentence that says carbon cannot remove the oxygen from a more reactive metal oxide.
9
Give one benefit and one cost of recycling glass, in one sentence. Accept any answer that gives saving raw materials as a benefit and sorting by colour as a cost.

Total 26 marks. Allow about 26 minutes.

Exercise 19X  Exam-style questions

1
RExplain the difference between a finite and a renewable resource, in one or two sentences. Accept any answer that says finite resources cannot be replaced at the rate they are used, and renewable ones can be replaced.[3 marks]
2
RName the method used to extract aluminium and explain why, in one sentence. Accept electrolysis, because aluminium is more reactive than carbon.[2 marks]
3
FName the four stages of a life cycle assessment. Write the four stages.[2 marks]
4
FGive two benefits of recycling metals, in one or two sentences. Accept any two of: saves ore, saves energy, reduces landfill, reduces pollution from extraction.[2 marks]
5
RExplain why sustainable use of resources matters, in two sentences. Accept any answer that says it meets today’s needs without harming future generations, and conserves finite resources.[3 marks]
6
RCompare two products using an LCA, in two sentences. Accept any answer that compares the impact at each stage and chooses the product with the lower overall impact, with a reason.[3 marks]
7
R[H] Explain why ammonia from the Haber process is important for farming, in one sentence. Accept any sentence that says it is used to make nitrogen fertilisers that help crops grow.[2 marks]
8
F[H] Name the three main plant nutrients, using their symbols. Write the three symbols.[2 marks]
9
RExplain why recycling plastics saves crude oil, in one sentence. Accept any sentence that says plastics are made from crude oil, so using recycled plastic means less new crude oil is needed.[2 marks]
10
REvaluate whether recycling is always the best option for a product, in two sentences. Accept any answer that says recycling costs energy and money, so an LCA should compare it with other options.[3 marks]
11
R[H] Explain why the reduction of iron oxide is a reduction, in one sentence. Accept any sentence that says the iron oxide loses oxygen when it forms iron.[2 marks]
← Chapter 18: Earth’s atmosphere, climate and water treatment

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