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
Elements, Compounds and Mixtures
Uses and risks of nanoparticulate materials
- 2 things to know
- Paper 1
Overview
Uses of nanoparticles in sun creams, wound dressings, catalysts, sports equipment, self-cleaning glass, electronics and medicine delivery, why their colour can differ from the bulk, and the risks of them entering cells, lungs and the bloodstream, harming river bacteria and being highly reactive, with the uncertain long-term effects, the limits of ordinary safety tests and the case for labelling.
What you need to know
Answer each one before you reveal it.
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Key term
How does a nanoparticle coating make glass self-cleaning?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Why are nanoparticles used in sun creams?
Model answer
Because they block ultraviolet light very effectively while being too small to scatter visible light, so the cream is transparent rather than white.
- 2
Why are silver nanoparticles added to wound dressings and to some fabrics?
Model answer
Because silver nanoparticles kill bacteria, so they keep wounds free of infection and stop clothing smelling.
- 3
Why are nanoparticles used as catalysts in industry?
Model answer
Because their huge surface area for a given mass speeds up reactions, so far less of the expensive catalyst is needed.
- 4
Why are carbon nanotubes added to sports equipment and other composite materials?
Model answer
Because they are extremely strong and very light, so they reinforce the material without adding much mass.
- 5
How does a nanoparticle coating make glass self-cleaning?
Model answer
A coating of titanium dioxide nanoparticles breaks down dirt in sunlight and spreads water into a sheet that washes the residue away.
- 6
Why are nanoparticles useful in electronics?
Model answer
Because materials such as carbon nanotubes conduct electricity and are minute, so they allow circuits and sensors to be made much smaller.
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