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
Predicting and Identifying Reactions
Predicting reactivity from the Periodic Table
- 3 things to know
- Paper 2
Overview
Where metals and non-metals sit, why a group reacts alike, caesium in water, the formulae of potassium iodide and calcium chloride, chlorine displacing iodine, why argon does not react, and recognising a Group 1 metal.
What you need to know
Answer each one before you reveal it.
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Key term
Where are the metals and the non-metals found in the Periodic Table?
Key term
Predict the formula of the compound formed between potassium and iodine.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Where are the metals and the non-metals found in the Periodic Table?
Model answer
Metals are on the left and in the centre, and non-metals are on the right-hand side.
- 2
Why do elements in the same group of the Periodic Table react in similar ways?
Model answer
They have the same number of electrons in their outer shell, so they form ions of the same charge and behave alike chemically.
- 3
Caesium lies at the bottom of Group 1. Predict what happens when it is added to cold water.
Model answer
It reacts explosively, forming caesium hydroxide solution and hydrogen gas.
- 4
Predict the formula of the compound formed between potassium and iodine.
Model answer
KI, because potassium loses one electron and iodine gains one.
- 5
Calcium is in Group 2. Predict the formula of the compound it forms with chlorine.
Model answer
CaCl₂, because a calcium atom loses two electrons and each chlorine atom gains one.
- 6
Predict what is seen when chlorine solution is added to colourless sodium iodide solution.
Model answer
The solution turns brown as iodine is displaced, because chlorine is more reactive than iodine.
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