Key term
OCR GCSE Chemistry A J248
Chemical Reactions
Topic overviewWriting formulae of elements and compoundsBalanced equations, and deducing formulae from ionsIonic equations, and state symbolsThe mole and the Avogadro constantConservation of mass, and changes of mass in open systemsStoichiometry, and calculating reacting massesExothermic and endothermic reactions, and reaction profilesActivation energy, and bond energy calculationsOxidation and reduction, by oxygen and by electronsAcids, alkalis and neutralisationThe ionic equation for neutralisation, and reactions of acidsDilute and concentrated, weak and strongThe pH scale, and hydrogen ion concentrationpH as a factor of ten, and measuring pHProducts 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 electrolysisBiological methods of metal extractionRate against yield in industry, and reaction conditionsThe 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 polymerisationCondensation polymerisation, and making a polymerDNA 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 overviewConcentration in mol/dm³, and titrationTitration calculations, and the mass of a soluteMolar gas volume and the volumes of gasesTheoretical mass and percentage yieldAtom economy, and choosing a reaction pathwayMeasuring the rate of a reaction, and rate graphsFactors affecting rate, and collision theorySurface area and rateCatalysts and how they workReversible reactions and dynamic equilibriumChanging the conditions of an 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
Predicting and Identifying Reactions
Transition metals
- 3 things to know
- Paper 4
Overview
How transition metals compare with Group 1 metals in melting point, density and reactivity, ions with different charges and the Roman numerals that show them, the colours of copper and iron ions, nickel as the catalyst for margarine, and copper for water pipes.
What you need to know
Answer each one before you reveal it.
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Key term
What is meant by saying that transition metals form ions with different charges? Give an example.
Key term
What colours are solutions containing copper(II) ions, iron(II) ions and iron(III) ions?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How do the melting points and densities of the transition metals compare with those of the Group 1 metals?
Model answer
Transition metals have much higher melting points and much higher densities, so they are hard, strong and heavy compared with the soft, light Group 1 metals.
- 2
How does the reactivity of a typical transition metal compare with that of a Group 1 metal?
Model answer
It is far less reactive, reacting only slowly or not at all with water and oxygen, while Group 1 metals react vigorously with cold water.
- 3
What is meant by saying that transition metals form ions with different charges? Give an example.
Model answer
The same metal can form more than one kind of positive ion, for example iron forms both Fe²⁺ and Fe³⁺.
- 4
What colours are solutions containing copper(II) ions, iron(II) ions and iron(III) ions?
Model answer
Copper(II) solutions are blue, iron(II) solutions are pale green and iron(III) solutions are orange-brown.
- 5
Name the transition metal used as the catalyst when hydrogen is added to vegetable oils to make margarine.
Model answer
Nickel.
- 6
Give the formulae of iron(II) chloride and iron(III) chloride, and explain why the names need Roman numerals.
Model answer
FeCl₂ and FeCl₃; iron forms both Fe²⁺ and Fe³⁺ ions, so the numeral shows which ion the compound contains.
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