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
Quantitative Chemistry
Conservation of mass and balanced chemical equations
- 3 things to know
- Paper 1
Overview
The law of conservation of mass, calculating masses in sealed reactions, why reactions are shown by balanced equations, balancing the equations for hydrogen and methane burning, the difference between balancing numbers and subscripts, and counting atoms in formulae such as 3H₂SO₄ and 2Ca(OH)₂.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Explain why the total mass inside a sealed container does not change when a reaction happens in it.
Key term
Give the balancing numbers needed for the equation H₂ + O₂ → H₂O.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the law of conservation of mass.
Model answer
No atoms are lost or made during a chemical reaction, so the total mass of the products equals the total mass of the reactants.
- 2
In a reaction carried out in a sealed flask, 8 g of one reactant reacts completely with 12 g of another to give a single product. What mass of product forms?
Model answer
20 g, because the mass of the product must equal the total mass of the reactants.
- 3
24 g of magnesium reacts completely with oxygen to form 40 g of magnesium oxide. What mass of oxygen reacted?
Model answer
16 g, since the mass of the product equals the total mass of the reactants.
- 4
Explain why the total mass inside a sealed container does not change when a reaction happens in it.
Model answer
The atoms present are only rearranged into new substances, and none are lost or made, so the total mass stays the same.
- 5
Explain why chemical reactions can be represented by balanced symbol equations.
Model answer
Because no atoms are lost or made, the number of atoms of each element must be the same on both sides of the equation.
- 6
What does it mean to say that a symbol equation is balanced?
Model answer
There are the same numbers of atoms of each element on the left-hand side as on the right-hand side.
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