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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
- 10 subtopics
- 30 things to know
- Chemistry Paper 2
What The Rate and Extent of Chemical Change covers
The Rate and Extent of Chemical Change is examined in Chemistry Paper 2. It covers measuring the mean rate of a reaction, rate from graphs, and the gradient of a tangent, factors which affect the rates of chemical reactions, collision theory and activation energy, catalysts, reversible reactions and dynamic equilibrium, the effect of changing conditions on equilibrium, the effect of changing concentration, the effect of temperature changes on equilibrium and the effect of pressure changes on equilibrium.
Where it is assessed
Chemistry Paper 2
Combined Science: Trilogy, Chemistry Paper 2: 1 hour 15 minutes, 70 marks, 16.7% of the qualification.
Check the AQA specification ↗The 10 subtopics
Each one has its own page.
- Measuring the mean rate of a reactionFollowing the quantity of reactant used or product formed over time, using a balance for a gas-producing reaction, the mean rate equations, worked calculations, and the units g/s and cm³/s.Open →
- Rate from graphs, and the gradient of a tangentRate in mol/s, the shape of a volume against time graph and what a horizontal section means, drawing a tangent to find the rate at one moment and calculating its gradient, why a curve is steepest at the start and flattens, plotting graphs with a line of best fit, y = mx + c, gradients and intercepts, and direct proportionality.Open →
- Factors which affect the rates of chemical reactionsThe five factors that affect rate, the effects of concentration, temperature, surface area, gas pressure and catalysts, investigating concentration by gas volume and by the disappearing cross, why rate is proportional to one over the time taken, identifying variables, and writing a hypothesis.Open →
- Collision theory and activation energyThe two conditions for colliding particles to react and activation energy, what collision theory explains, why higher concentration, gas pressure, surface area and temperature make collisions more frequent or more energetic, surface area to volume ratio, predicting rate changes when conditions are altered, and the symbols for proportionality, much less than, much greater than and approximately.Open →
- CatalystsWhat a catalyst is and why little is needed, why different reactions need different catalysts, enzymes as biological catalysts, how a catalyst provides a pathway with lower activation energy without changing the amount of product or the energy change, its effect on a reaction profile, identifying one, and industrial uses.Open →
- Reversible reactions and dynamic equilibriumReversible reactions and the ⇌ symbol, forward and reverse reactions and changing direction by altering conditions, heating and rehydrating copper sulfate, equal energy transferred in each direction, the closed system needed for equilibrium, and equilibrium as forward and reverse reactions continuing at the same rate.Open →
- The effect of changing conditions on equilibriumHow conditions fix the relative amounts at equilibrium, how a system counteracts a change, Le Chatelier's Principle, what a position lying to the right means, and the ammonia equilibrium under changes of temperature, pressure and concentration.Open →
- The effect of changing concentrationWhat happens to a mixture when one concentration changes, why the whole system shifts, the effects of adding a reactant or removing or adding a product, and the hydrogen iodide and ammonia equilibria as examples.Open →
- The effect of temperature changes on equilibriumWhy raising the temperature shifts an equilibrium in the endothermic direction and lowering it in the exothermic direction, the effect on yield for each type of forward reaction, ammonia and N₂O₄ as examples, and the compromise industrial temperature.Open →
- The effect of pressure changes on equilibriumWhich 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.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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Describe the disappearing cross method for investigating how concentration affects rate, how the time relates to rate, and why one person judges the end point.
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For hydrogen iodide and ammonia equilibria, explain what happens when a product is removed or a reactant reduced, and why industry removes product continuously.
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Name the independent variable, the dependent variable and two control variables in an investigation of how concentration affects rate.
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Name the two kinds of measurement that can be followed over time to find the rate of a chemical reaction.
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Give the unit of rate of reaction used when the quantity of reactant is measured in moles.
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State the two conditions that must be met when reacting particles meet if a reaction is to happen.
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Define a catalyst.
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Describe the symbol written between the reactants and the products of a reversible reaction.
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State what decides the relative amounts of reactants and products present in a mixture at equilibrium.
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Explain why raising the temperature of a mixture at equilibrium disturbs it.
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State the kind of equilibrium mixture whose position of equilibrium is altered by a change in pressure.
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Explain why a single measurement of the mass of product made is not enough to give the rate of a reaction.
Numbers
A reaction uses 0.05 mol of a reactant in 25 s. Calculate the mean rate of reaction in mol/s.
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Explain why not every collision between reacting particles produces a reaction.
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Explain why only a small amount of a catalyst is needed even for a reaction that is run many times.
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In the reversible reaction A + B ⇌ C + D, name the substances that are the products of the reverse reaction.
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State how a system at equilibrium responds when one of the conditions is changed.
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The forward reaction of a reversible reaction is endothermic. State the effect of raising the temperature on the relative amount of products at equilibrium.
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Explain why a change in pressure has no effect on the position of an equilibrium between substances dissolved in solution.
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Describe how a balance can be used to follow the rate of a reaction that gives off a gas.
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Explain why the rate of the same reaction can be quoted in g/s, in cm³/s or in mol/s.
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Name the five factors that affect the rate of a chemical reaction.
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Explain, using collision theory, why increasing the pressure of reacting gases increases the rate of reaction.
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Describe how the reaction profile of a catalysed reaction differs from that of the same reaction without a catalyst.
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State what has to be altered to change the direction in which a reversible reaction goes.
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Explain what counteracting the change means when the concentration of a reactant in an equilibrium mixture is increased.
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Describe what happens to a mixture at equilibrium immediately after the concentration of one of the substances in it is changed.
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The forward reaction of a reversible reaction is exothermic. State the effect of raising the temperature on the relative amount of products at equilibrium.
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Describe how you work out which side of a gaseous equilibrium has the smaller number of molecules.
Take The Rate and Extent of Chemical Change further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Reversible reaction vs Equilibrium
Reversible reaction: one whose products can react together to re-form the reactants. Equilibrium: the state where the forward and reverse reactions run at the same rate.
Activation energy vs Rate of reaction
Activation energy: the minimum energy that particles must have to react when they collide. Rate of reaction: how quickly reactant is used up or product is formed.
Concentration vs Pressure
Concentration: how many reacting particles are in a given volume of solution. Pressure: how closely packed the particles of reacting gases are.
Questions from this topic
Each one with the model answer underneath.
- 1
Name the two kinds of measurement that can be followed over time to find the rate of a chemical reaction.
Model answer
The quantity of a reactant used up, or the quantity of a product formed.
- 2
Explain why a single measurement of the mass of product made is not enough to give the rate of a reaction.
Model answer
Rate compares how much is made or used with how long it took, so the time taken must be measured as well.
- 3
Describe how a balance can be used to follow the rate of a reaction that gives off a gas.
Model answer
The reaction vessel is stood on a balance and the mass is recorded at regular times; the mass falls as the gas escapes.
- 4
State the equation for the mean rate of a reaction written in terms of the reactant.
Model answer
Mean rate of reaction = quantity of reactant used ÷ time taken.
- 5
A reaction uses up 2.4 g of magnesium in 60 s. Calculate the mean rate of reaction.
Model answer
2.4 g ÷ 60 s = 0.04 g/s.
- 6
A reaction uses 6.0 g of a reactant at a mean rate of 0.25 g/s. Calculate the time taken.
Model answer
6.0 g ÷ 0.25 g/s = 24 s.
What is inside Levo
Six ways to work the same material.
The Rate and Extent of Chemical Change revision questions
- What does The Rate and Extent of Chemical Change cover in AQA GCSE Combined Science Chemistry?
- 10 subtopics: measuring the mean rate of a reaction, rate from graphs, and the gradient of a tangent, factors which affect the rates of chemical reactions, collision theory and activation energy, catalysts, reversible reactions and dynamic equilibrium, the effect of changing conditions on equilibrium, the effect of changing concentration, the effect of temperature changes on equilibrium and the effect of pressure changes on equilibrium. Each one has its own page with questions and model answers.
- How is The Rate and Extent of Chemical Change organised?
- By the AQA 8464 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in The Rate and Extent of Chemical Change, on a schedule.
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