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
Global Challenges
Fractional distillation of crude oil
- 2 things to know
- Paper 4
Overview
What 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.
What you need to know
Answer each one before you reveal it.
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Key term
Name the fractions obtained from crude oil, from the top of the column downwards.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is crude oil?
Model answer
A mixture of a very large number of hydrocarbons, most of them alkanes, formed over millions of years from the buried remains of ancient organisms.
- 2
Describe how crude oil is separated by fractional distillation.
Model answer
The oil is heated until it vaporises and fed into a tall column that is hot at the bottom and cool at the top; each fraction condenses at the level where the temperature falls below its boiling range and is drawn off there.
- 3
Name the fractions obtained from crude oil, from the top of the column downwards.
Model answer
Refinery gases, petrol, kerosene, diesel oil, fuel oil and bitumen.
- 4
Which fraction leaves at the very top of the fractionating column?
Model answer
The refinery gases.
- 5
Which fraction is collected at the base of the column, and what is it used for?
Model answer
Bitumen, which is used for surfacing roads and roofs.
- 6
What is kerosene used for?
Model answer
It is used as fuel for aircraft.
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