Global Challenges

What Global Challenges covers

Global Challenges is examined in Chemistry A Paper 4. It covers extracting metals by reduction and by electrolysis; biological methods of metal extraction; rate against yield in industry and reaction conditions; the Haber process and fertiliser production; nitrogen, phosphorus and potassium in agriculture; life cycle assessment; recycling and the decisions behind it; alloys and the corrosion of metals; comparing glass, ceramics, polymers, composites and metals; functional groups and homologous series; predicting the products of organic reactions; addition polymerisation; condensation polymerisation and making a polymer; DNA and other natural polymers; fractional distillation of crude oil; the fractions and crude oil as a feedstock; dependence on hydrocarbons and cracking; chemical cells and fuel cells; the Earth's early atmosphere and how oxygen developed; the greenhouse effect and evidence for climate change; the effects of carbon dioxide and methane, and air pollutants; and producing potable water.

The 22 subtopics

Each one has its own page.

• Extracting metals by reduction and by electrolysisReduction by carbon for metals below carbon, the blast furnace and its raw materials, why aluminium needs electrolysis, bauxite and cryolite, the electrodes in aluminium extraction, and the cost of each method.Open →
• Biological methods of metal extractionBioleaching with bacteria and phytoextraction with plants as ways to obtain metals from low-grade ores, how each works, recovering copper from a leachate by displacement with scrap iron or by electrolysis, why the ash is useful, their environmental and economic advantages, their slow rate and toxic leachate as drawbacks, and why these methods are becoming more important.Open →
• Rate against yield in industry, and reaction conditionsThe Haber and Contact equilibria, how temperature and pressure change yield and rate, the compromise conditions, what a catalyst does to yield, reading rate and yield graphs, and where the nitrogen and hydrogen come from.Open →
• The Haber process and fertiliser productionWhat the ammonia from the Haber process is mainly used for, why crops need nitrogen compounds and how cheap fertiliser raises food production, where farmers got nitrogen before, the algal growth that fertiliser run-off causes, preparing ammonium sulfate by titration and crystallisation in the laboratory, and how industrial production differs in scale, acid concentration, automation and continuous running.Open →
• Nitrogen, phosphorus and potassium in agricultureThe three elements in an NPK fertiliser and what nitrogen, phosphorus and potassium each do for a plant, why fertiliser compounds must be soluble, choosing a fertiliser for a leaf crop, making ammonium nitrate and ammonium sulfate by neutralisation, fertiliser manufacture as a set of integrated processes with its nitric acid, Contact process and raw materials, and crystallising the solid salt.Open →
• Life cycle assessmentThe four stages of a life cycle assessment, placing quarrying, product use, transport and landfill in them, what is measured at each stage, and why comparing two products fairly is difficult.Open →
• Recycling, and the decisions behind itHow plastic bottles become fleece and why that is easier than making new bottles, recycling glass and car tyres for other uses, why recycling aluminium saves so much energy, why sorting comes first and recycled material is often lower grade, the resources saved, and the costs, contamination, scarcity, market prices and social factors that decide whether recycling is worthwhile.Open →
• Alloys, and the corrosion of metalsWhat an alloy is and why it is harder than the pure metal, the make-up and uses of steel, brass, bronze, solder and duralumin, what corrosion is, the conditions for rusting and the experiment that shows them, why salt speeds it up, why aluminium and copper are protected by their corrosion layers, and preventing rusting with barriers, galvanising and sacrificial protection by zinc or magnesium.Open →
• Comparing glass, ceramics, polymers, composites and metalsHow metals, ceramics, polymers, glass and composites compare in toughness, density, melting point, conductivity and strength, what a composite is, and choosing materials for windows, furnaces, bicycles, cables, kettles and bridges.Open →
• Functional groups and homologous seriesWhat a homologous series and a functional group are, the general formulae of the alkanes, alkenes, alcohols and carboxylic acids, the C=C and –OH groups, identifying a series from a molecular formula, the first four members of each series, the formulae of propane, but-1-ene and ethanoic acid, and how the atoms in ethene are joined.Open →
• Predicting the products of organic reactionsThe products and equations for the complete combustion of propane and ethanol, adding bromine or hydrogen across the double bond of an alkene and the bromine water test, oxidising alcohols such as ethanol to carboxylic acids, why the functional group decides the reactions of a whole homologous series, and using it to predict the products of unfamiliar compounds.Open →
• Addition polymerisationWhat addition polymerisation, a monomer and a repeating unit are, the C=C double bond a monomer needs and what happens to it, why there is only one product, poly(ethene), poly(propene), poly(chloroethene) and poly(tetrafluoroethene), what n and the end bonds show in a polymer formula, and working out the monomer from a repeating unit.Open →
• Condensation polymerisation, and making a polymerWhat condensation polymerisation is, the two functional groups a monomer needs, the water released at each link, the monomers and links of polyesters and polyamides, and making a polyamide or polyester in the laboratory.Open →
• DNA and other natural polymersNucleotides as the monomers of DNA, its four bases, why DNA counts as a polymer, its double helix shape and its job of carrying genetic instructions, proteins as polymers of amino acids, and starch and cellulose as polymers of glucose.Open →
• Fractional distillation of crude oilWhat crude oil is and how fractional distillation separates it in a column that is hot at the bottom and cool at the top, the fractions from refinery gases to bitumen and their uses, why larger hydrocarbons have higher boiling points and condense lower down, which forces are overcome on boiling, and why a fraction boils over a range of temperatures.Open →
• The fractions, and crude oil as a feedstockThe alkanes and their general formula CₙH₂ₙ₊₂, what a hydrocarbon is, working out and naming alkane formulae such as C₈H₁₈ and pentane, what saturated means, why a fraction is not pure, crude oil as the feedstock of the petrochemical industry for polymers, solvents, lubricants and medicines, how crude oil formed, and ethene for poly(ethene).Open →
• Dependence on hydrocarbons, and crackingWhy crude oil is finite and how modern life and transport depend on hydrocarbons, rising costs, arguments against burning oil, uses that do not burn it, pollution concerns, why replacing hydrocarbon fuels is hard, what cracking is and why refineries do it, the conditions for catalytic and steam cracking, its products and equation, and the ethical case against burning oil so quickly.Open →
• Chemical cells and fuel cellsWhat a chemical cell is, why it runs until a reactant is used up and a battery goes flat, the electrolyte and the difference in reactivity that sets the potential difference, making a cell last longer, the hydrogen–oxygen fuel cell with its equation, electrodes and water product, its advantages and disadvantages in cars and spacecraft, and whether a hydrogen car is free of carbon dioxide emissions.Open →
• The Earth's early atmosphere, and how oxygen developedThe composition of today's atmosphere, the volcanic gases of the early atmosphere, why ideas about it are uncertain and the evidence used, how carbon dioxide dissolved in the oceans and was locked into carbonate rocks and fossil fuels, how photosynthesis slowly produced oxygen and its equation, why oxygen mattered for life, and why nitrogen became the most abundant gas.Open →
• The greenhouse effect, and evidence for climate changeThree greenhouse gases, how the greenhouse effect traps infrared radiation and why life needs it, the effect of more greenhouse gas, the correlation between fossil fuel use and carbon dioxide, ice core evidence, the uncertainty in the evidence and in climate predictions, judging climate claims, peer review, communicating findings, and the ethics of cutting emissions.Open →
• Effects of carbon dioxide and methane, and air pollutantsThe effects of rising carbon dioxide and methane such as warming and rising sea levels, sources of methane, ways to cut emissions including carbon capture and storage and planting trees, why global action is hard, the sources and harm of carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates, and presenting and sampling pollution data with bar charts, histograms and frequency tables.Open →
• Producing potable waterWhat potable water is and how it differs from pure water, treating fresh water by screening, filtering and sterilising with chlorine, ozone or ultraviolet light, desalination by distillation or reverse osmosis and its cost, how hard ground, salt and waste water are to treat, and taking random, representative samples from a reservoir.Open →

What you need to know

Answer each one before you reveal it.

Take Global Challenges further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Bioleaching vs Phytoextraction

  Bioleaching: bacteria break down low-grade ore to give a copper leachate. Phytoextraction: plants absorb metal compounds and are burned to a metal-rich ash.

• Addition polymerisation vs Condensation polymerisation

  Addition polymerisation: unsaturated monomers join into one chain with no other product. Condensation polymerisation: monomers join with a small molecule such as water released at each link.

• Alkane vs Alkene

  Alkane: saturated hydrocarbon with only single bonds, general formula CₙH₂ₙ₊₂. Alkene: hydrocarbon with a carbon–carbon double bond, general formula CₙH₂ₙ.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What does the position of a metal relative to carbon in the reactivity series tell you about how it can be extracted?

   Model answer

   A metal less reactive than carbon can be extracted by heating its ore with carbon, while a more reactive metal cannot.

2. 2

   Why is carbon able to remove the oxygen from iron oxide?

   Model answer

   Carbon is more reactive than iron, so it takes the oxygen from the iron oxide and is itself oxidised.

3. 3

   In terms of oxygen, what happens to a metal oxide when it is reduced by carbon?

   Model answer

   The metal oxide loses its oxygen to the carbon, leaving the metal behind.

4. 4

   Name the raw materials fed into a blast furnace to extract iron.

   Model answer

   Iron ore, coke, limestone and hot air.

5. 5

   Which gas formed inside a blast furnace does most of the reducing of the iron ore?

   Model answer

   Carbon monoxide.

6. 6

   Give a word equation for the reduction of iron(III) oxide by carbon.

   Model answer

   Iron(III) oxide + carbon → iron + carbon dioxide.

What is inside Levo

Six ways to work the same material.

Global Challenges revision questions

What does Global Challenges cover in OCR GCSE Chemistry A?

22 subtopics: extracting metals by reduction and by electrolysis, biological methods of metal extraction, rate against yield in industry, and reaction conditions, the haber process and fertiliser production, nitrogen, phosphorus and potassium in agriculture, life cycle assessment, recycling, and the decisions behind it, alloys, and the corrosion of metals, comparing glass, ceramics, polymers, composites and metals, functional groups and homologous series, predicting the products of organic reactions, addition polymerisation, condensation polymerisation, and making a polymer, dna and other natural polymers, fractional distillation of crude oil, the fractions, and crude oil as a feedstock, dependence on hydrocarbons, and cracking, chemical cells and fuel cells, the earth's early atmosphere, and how oxygen developed, the greenhouse effect, and evidence for climate change, effects of carbon dioxide and methane, and air pollutants and producing potable water. Each one has its own page with questions and model answers.

How is Global Challenges organised?

By the OCR J248 specification, subtopic by subtopic, so it matches the order you are taught it in.