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
Energy Changes
- 4 subtopics
- 12 things to know
- Chemistry Paper 1
What Energy Changes covers
Energy Changes is examined in Chemistry Paper 1. It covers exothermic and endothermic reactions, everyday uses, and investigating temperature change, reaction profiles and the energy change of reactions.
Where it is assessed
Chemistry Paper 1
Combined Science: Trilogy, Chemistry Paper 1: 1 hour 15 minutes, 70 marks, 16.7% of the qualification.
Check the AQA specification ↗The 4 subtopics
Each one has its own page.
- Exothermic and endothermic reactionsConservation of energy in reactions, exothermic reactions that transfer energy to the surroundings and raise their temperature, examples such as combustion, oxidation and neutralisation, self-heating cans and hand warmers, and endothermic reactions that take in energy and lower the temperature of the surroundings.Open →
- Everyday uses, and investigating temperature changeThermal decomposition and the citric acid and sodium hydrogencarbonate reaction, cold packs, hand warmers, reading energy change from a thermometer, and measuring temperature change in an insulated cup with the variables controlled.Open →
- Reaction profilesThe two conditions for colliding particles to react, activation energy and why not every collision leads to a reaction, what a reaction profile shows, reading the overall energy change and activation energy from it, and the profiles of exothermic and endothermic reactions.Open →
- The energy change of reactionsBreaking bonds as endothermic and making bonds as exothermic, bond energy, calculating the overall energy change from the energy needed to break reactant bonds and the energy released forming product bonds, why the change is negative for exothermic and positive for endothermic reactions, and worked bond energy calculations.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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Explain what a high activation energy means for a reaction's rate, what particles must have to react, and what a reaction profile shows.
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Explain why a reaction can be exothermic overall even though energy has to be supplied to start it.
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If a reaction transfers energy to its surroundings, how does the energy stored in the products compare with the energy stored in the reactants?
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Which two substances are mixed in a well known endothermic reaction that makes the temperature of the mixture fall?
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A reaction transfers 200 kJ of energy to the surroundings. By how much has the energy stored in the chemicals fallen?
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Give one everyday application of an endothermic reaction.
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State the two conditions that must be met before colliding particles will react.
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A student mixes two solutions in a beaker and the beaker becomes warm. What type of energy change has taken place?
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A reaction mixture becomes noticeably colder as it proceeds. State what this tells you about the direction of the energy transfer.
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Explain why not every collision between reactant particles leads to a reaction.
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What two kinds of change to chemical bonds take place in every chemical reaction?
Take Energy Changes further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Exothermic vs Endothermic
Exothermic: a reaction transferring energy to the surroundings, raising their temperature. Endothermic: a reaction taking in energy from the surroundings, lowering their temperature.
Activation energy vs Overall energy change
Activation energy: the minimum energy that colliding particles need in order to react. Overall energy change: the difference between the reactants' and products' levels on a reaction profile.
Bond breaking vs Bond making
Bond breaking: the endothermic step that takes in the supplied energy at the start. Bond making: the exothermic step that releases energy as the products form.
Questions from this topic
Each one with the model answer underneath.
- 1
What happens to the total amount of energy in the universe during a chemical reaction?
Model answer
It stays exactly the same, because energy is conserved in chemical reactions.
- 2
If a reaction transfers energy to its surroundings, how does the energy stored in the products compare with the energy stored in the reactants?
Model answer
The product molecules store less energy than the reactants, by exactly the amount of energy transferred out.
- 3
A reaction transfers 200 kJ of energy to the surroundings. By how much has the energy stored in the chemicals fallen?
Model answer
By 200 kJ, because the energy gained by the surroundings is exactly the energy the chemicals have lost.
- 4
Define an exothermic reaction.
Model answer
It is a reaction that transfers energy to the surroundings.
- 5
What happens to the temperature of the surroundings during an exothermic reaction?
Model answer
It increases.
- 6
A student mixes two solutions in a beaker and the beaker becomes warm. What type of energy change has taken place?
Model answer
An exothermic change, because energy has been transferred from the reaction to the surroundings.
What is inside Levo
Six ways to work the same material.
Energy Changes revision questions
- What does Energy Changes cover in AQA GCSE Combined Science Chemistry?
- 4 subtopics: exothermic and endothermic reactions, everyday uses, and investigating temperature change, reaction profiles and the energy change of reactions. Each one has its own page with questions and model answers.
- How is Energy Changes organised?
- By the AQA 8464 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Energy Changes, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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