Key term
AQA GCSE Combined Science Chemistry 8464
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 7
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 fullerenes
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 neutralisationStrong 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
Quantitative Chemistry
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
The Rate and Extent of Chemical Change
The effect of pressure changes on equilibrium
- 3 things to know
- Chemistry Paper 2
Overview
Which equilibria respond to pressure and why solutions do not, shifting towards fewer or more molecules, counting gas molecules from balancing numbers, and predictions for the ammonia, sulfur dioxide, N₂O₄ and hydrogen iodide equilibria.
What you need to know
Answer each one before you reveal it.
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Key term
Explain why a change in pressure has no effect on the position of an equilibrium between substances dissolved in solution.
Key term
Describe how you work out which side of a gaseous equilibrium has the smaller number of molecules.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the kind of equilibrium mixture whose position of equilibrium is altered by a change in pressure.
Model answer
One in which the reactants and products include gases.
- 2
Explain why a change in pressure has no effect on the position of an equilibrium between substances dissolved in solution.
Model answer
A change in pressure alters how closely gas particles are packed together, and there are no gases present to be affected.
- 3
State the direction in which the position of a gaseous equilibrium shifts when the pressure is increased.
Model answer
It shifts towards the side with the smaller number of molecules.
- 4
State the direction in which the position of a gaseous equilibrium shifts when the pressure is decreased.
Model answer
It shifts towards the side with the larger number of molecules.
- 5
Describe how you work out which side of a gaseous equilibrium has the smaller number of molecules.
Model answer
Add up the balancing numbers in front of the gases on each side of the symbol equation and compare the two totals.
- 6
Explain why increasing the pressure shifts a gaseous equilibrium towards the side with fewer molecules.
Model answer
Fewer gas molecules exert a lower pressure, so shifting that way opposes the increase in pressure that was made.
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