Key term
AQA GCSE Chemistry 8462
Atomic Structure and the Periodic Table
Topic overviewAtoms, elements and compoundsWord equations, symbols and balanced equationsMixturesFrom the plum pudding model to the nuclear modelBohr, Chadwick and the modern model of the atomRelative electrical charges of subatomic particlesSize and mass of atomsRelative atomic mass and electronic structureThe periodic tableDevelopment of the periodic tableMetals and non-metalsGroup 0Group 1Group 7Transition metals, and how they differ from Group 1
Bonding, Structure, and the Properties of Matter
Topic overviewChemical bonds, including metallic bondingIonic bondingIonic compoundsCovalent bonding and how it is representedThe three states of matter and changes of statePredicting state, state symbols, and the limits of the particle modelProperties of ionic compoundsProperties of small moleculesPolymers and giant covalent structuresProperties of metals and alloys, and why metals conductDiamond and graphiteGraphene and fullerenesSizes of particles and their propertiesUses of nanoparticles
Chemical Analysis
Chemical Changes
Topic overviewThe reactivity seriesMetal oxides, extraction, and redox in terms of electronsAcids reacting with metals, neutralisation and saltsSoluble saltsThe pH scale and neutralisationTitrationsStrong and weak acidsThe process of electrolysis, and molten ionic compoundsUsing electrolysis to extract metalsElectrolysis of aqueous solutionsRepresentation of reactions at electrodes as half equations
Chemistry of the Atmosphere
Topic overviewThe Earth's early atmosphereHow oxygen increased and carbon dioxide decreasedThe gases in today's atmosphere, and which are greenhouse gasesHuman activities which contribute to an increase in greenhouse gases in the atmosphereGlobal climate change and carbon footprintsAtmospheric pollutants from fuels, and their effects
Energy Changes
Organic Chemistry
Topic overviewCrude oil, hydrocarbons and alkanesFractional distillation and petrochemicalsProperties of hydrocarbonsCracking, and testing alkenes with bromine waterWhy cracking is useful, and equations for itStructure and formulae of alkenesReactions of alkenesAlcoholsCarboxylic acidsAddition polymerisationCondensation polymerisationAmino acids, DNA and naturally occurring polymers
Quantitative Chemistry
Topic overviewConservation of mass and balanced chemical equationsRelative formula mass and concentration of solutionsMass changes when a gas is involved, and measurement uncertaintyMolesAmounts of substances in equations, and balancing using molesLimiting reactantsPercentage yieldAtom economyUsing concentrations of solutions in mol/dmUse of amount of substance in relation to volumes of gases
The Rate and Extent of Chemical Change
Topic overviewMeasuring the mean rate of a reactionRate from graphs, and the gradient of a tangentFactors which affect the rates of chemical reactionsCollision theory and activation energyCatalystsReversible reactions and dynamic equilibriumThe effect of changing conditions on equilibriumThe effect of changing concentrationThe effect of temperature changes on equilibriumThe effect of pressure changes on equilibrium
Using Resources
Topic overviewUsing the Earth's resources and sustainable developmentProducing potable water in the UKDesalination, and analysing water samplesWaste water treatmentAlternative methods of extracting metalsLife cycle assessmentWays of reducing the use of resourcesCorrosion and its preventionAlloys as useful materialsGlass, clay ceramics and polymersComposites, and comparing materialsThe Haber processProduction and uses of NPK fertilisers
Bonding, Structure, and the Properties of Matter
Covalent bonding and how it is represented
- 3 things to know
- Paper 1
Overview
What a covalent bond is, small molecules, polymers and giant covalent structures, recognising each from formulae, bonds drawn as lines, ball and stick models and shortened polymer formulae, dot and cross diagrams for molecules such as hydrogen, chlorine, water, ammonia and methane, the limits of two-dimensional diagrams, and deducing molecular and polymer formulae from models and diagrams.
What you need to know
Answer each one before you reveal it.
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Key term
Give two examples of substances that consist of small covalently bonded molecules.
Key term
How can you recognise from its chemical formula that a substance consists of small molecules?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is a covalent bond?
Model answer
A bond formed when two atoms share a pair of electrons.
- 2
How strong are the covalent bonds between the atoms in a molecule?
Model answer
They are very strong.
- 3
Give two examples of substances that consist of small covalently bonded molecules.
Model answer
Water, H₂O, and carbon dioxide, CO₂.
- 4
How can you recognise from its chemical formula that a substance consists of small molecules?
Model answer
The formula shows a small fixed number of non-metal atoms, as in NH₃ or CH₄.
- 5
Which covalently bonded substances have very large molecules?
Model answer
Polymers.
- 6
How does a polymer molecule differ from a molecule of methane?
Model answer
A polymer molecule contains very many atoms covalently bonded in a long repeating chain, while methane has only five atoms.
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