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
Chemistry of the Atmosphere
The Earth's early atmosphere
- 3 things to know
- Paper 2
Overview
Why the evidence is limited and theories keep changing, the volcanic origin of the gases and the oceans, carbon dioxide with little oxygen, the Mars and Venus comparison, and how carbon dioxide dissolved into carbonate sediments.
What you need to know
Answer each one before you reveal it.
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Key term
Why is the evidence about the Earth's early atmosphere so limited?
Key term
Why can scientists not be certain which account of the early atmosphere is correct?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Why is the evidence about the Earth's early atmosphere so limited?
Model answer
The Earth formed about 4.6 billion years ago, so almost no direct evidence of the conditions then has survived.
- 2
What has happened to scientific ideas about how the early atmosphere formed?
Model answer
They have changed and developed over time as new evidence and new interpretations have appeared.
- 3
Roughly how long ago did the Earth form?
Model answer
About 4.6 billion years ago.
- 4
Why can scientists not be certain which account of the early atmosphere is correct?
Model answer
The evidence is limited and indirect, so more than one theory can fit what is known.
- 5
What is thought to have released the gases that made up the Earth's early atmosphere?
Model answer
Intense volcanic activity during the first billion years of the Earth's existence.
- 6
How are the oceans thought to have formed?
Model answer
Water vapour released by volcanoes cooled and condensed to liquid water.
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