Key term
OCR GCSE Chemistry A J248
Chemical Reactions
Topic overviewWriting formulae of elements and compoundsBalanced equations, and deducing formulae from ionsState symbols in equationsConservation of mass, and changes of mass in open systemsExothermic and endothermic reactions, and reaction profilesActivation energy and why reactions need itOxidation and reduction in terms of oxygenAcids, alkalis and neutralisationThe ionic equation for neutralisation, and reactions of acidsThe pH scale, acidity and alkalinityMeasuring pH with indicators and pH metersProducts at the electrodes, and molten ionic compoundsElectrolysis of aqueous solutionsInert and non-inert electrodes
Elements, Compounds and Mixtures
Topic overviewPurity, and melting point dataRelative formula mass and empirical formulaeFormulations, and separating mixturesPaper and thin layer chromatographyInterpreting chromatograms and Rf valuesChoosing a purification methodMetals and non-metals in the Periodic TableElectron arrangement and position in the Periodic TableIonic, covalent and metallic bonding comparedDot and cross diagrams, and the limits of modelsReactions, electron arrangement and Mendeleev's tableCarbon's four bonds, and the variety of organic compoundsDiamond, graphite, fullerenes and grapheneBond strength, intermolecular forces and predicting stateBulk properties of ionic, molecular and giant structuresNanoparticles: size and surface area to volumeUses and risks of nanoparticulate materials
Global Challenges
Topic overviewExtracting metals by reduction and by electrolysisThe Haber process and fertiliser productionNitrogen, phosphorus and potassium in agricultureLife cycle assessmentRecycling, and the decisions behind itAlloys, and the corrosion of metalsComparing glass, ceramics, polymers, composites and metalsFunctional groups and homologous seriesPredicting the products of organic reactionsAddition polymerisationDNA and other natural polymersFractional distillation of crude oilThe fractions, and crude oil as a feedstockDependence on hydrocarbons, and crackingChemical cells and fuel cellsThe Earth's early atmosphere, and how oxygen developedThe greenhouse effect, and evidence for climate changeEffects of carbon dioxide and methane, and air pollutantsProducing potable water
Monitoring and Controlling Chemical Reactions
Topic overviewCarrying out an acid–alkali titrationTheoretical mass and percentage yieldAtom economy and its calculationMeasuring the rate of a reaction, and rate graphsFactors affecting rate, and collision theorySurface area and rateCatalysts and how they workReversible reactions and dynamic equilibriumActivation energy, and enzymes as catalysts
Particles
Predicting and Identifying Reactions
Topic overviewGroups 1, 7 and 0, and why they behave as they doTransition metalsPredicting reactivity from the Periodic TableReactivity of metals with water and acidsTests for oxygen, hydrogen, carbon dioxide and chlorineTests for aqueous cations and anionsFlame tests, and identifying metal ionsIdentifying a species from test resultsInstrumental methods of analysis
Chemical Reactions
Oxidation and reduction in terms of oxygen
- 3 things to know
- Paper 1
Overview
Oxidation and reduction as the gain and loss of oxygen, identifying what is oxidised and reduced when carbon reduces copper oxide, oxidising and reducing agents, carbon monoxide as the reducing agent for iron oxide, magnesium burning in air, and why oxidation and reduction always happen together.
What you need to know
Answer each one before you reveal it.
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Key term
Define oxidation in terms of oxygen.
Key term
Define reduction in terms of oxygen.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define oxidation in terms of oxygen.
Model answer
Oxidation is the gain of oxygen by a substance.
- 2
Define reduction in terms of oxygen.
Model answer
Reduction is the loss of oxygen from a substance.
- 3
In 2CuO + C → 2Cu + CO₂, state which substance is oxidised and which is reduced.
Model answer
Carbon is oxidised because it gains oxygen, and copper oxide is reduced because it loses oxygen.
- 4
What is an oxidising agent?
Model answer
A substance that oxidises another substance by giving oxygen to it, and is itself reduced.
- 5
What is a reducing agent?
Model answer
A substance that reduces another substance by taking oxygen away from it, and is itself oxidised.
- 6
In Fe₂O₃ + 3CO → 2Fe + 3CO₂, name the reducing agent and explain your choice.
Model answer
Carbon monoxide, because it removes oxygen from the iron oxide and is itself oxidised to carbon dioxide.
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