Key term
Edexcel GCSE Combined Science Chemistry 1SC0
Key Concepts in Chemistry
Topic overviewFormulae, word equations and balanced equationsHazard symbols and assessing riskThe changing model of the atomProtons, neutrons and electronsThe nucleus, mass number and atomic massElements and isotopesCalculating particle numbers and relative atomic massMendeleev's periodic tableHow the modern periodic table is arrangedElectronic configuration and the periodic tableHow ionic bonds formIons in ionic compoundsFormulae of ionic compoundsNaming compounds and the ionic latticeCovalent bonds and moleculesDot and cross diagrams for simple moleculesClassifying substances and the properties of ionic compoundsProperties of simple molecular substances, and forms of carbonGraphite and diamondFullerenes and graphenePolymers and models of bondingThe properties of metalsRelative formula mass and percentage compositionEmpirical and molecular formulaeConservation of mass in closed and open systemsReacting masses from balanced equationsConcentration in grams per cubic decimetre
States of Matter and Mixtures
Topic overviewThe three states of matter and changes of stateEnergy changes during changes of state, and predicting statePure substances and melting point dataChoosing a separation techniqueSeparating a mixture in practicePaper chromatography and interpreting a chromatogramInvestigating inks by distillation and chromatographyMaking water potable
Chemical Changes
Topic overviewAcids, alkalis and the pH scaleIndicators: litmus, methyl orange and phenolphthaleinInvestigating pH change when neutralising an acidBases and alkalisReactions of acids, and testing for hydrogen and carbon dioxideNeutralisation and its ionic equationPreparing soluble salts from insoluble and soluble reactantsPreparing pure, dry copper sulfate crystalsCarrying out an acid-alkali titrationSolubility rulesPredicting precipitates and preparing an insoluble saltElectrolytes and what electrolysis isMovement of ions and predicting the products of molten electrolysisElectrolysis with inert electrodesElectrolysis of copper sulfate solutionInvestigating the electrolysis of copper sulfate
Extracting Metals and Equilibria
Groups in the Periodic Table
Topic overviewThe groups of the periodic table, and the alkali metalsReactions of the alkali metals with waterThe pattern in alkali metal reactivity and why it happensPhysical properties of the halogensThe test for chlorine, and halogens reacting with metalsHydrogen halides, and explaining halogen reactivityDisplacement reactions of the halogensGroup 0: the noble gases
Rates of Reaction and Energy Changes
Fuels and Earth Science
Topic overviewHydrocarbons and crude oilFractional distillation and the fractionsProperties of the fractions and homologous seriesComplete and incomplete combustionCarbon monoxide and sootPollutants and acid rainHydrogen and fossil fuels comparedCracking and why it is necessaryThe Earth's early atmosphereHow the oceans formed and how oxygen appearedThe test for oxygen and the greenhouse gasesToday's atmosphere and evidence for climate change
Chemical Changes
Preparing soluble salts from insoluble and soluble reactants
- 3 things to know
- Paper 3
Overview
Why an excess of insoluble solid is used and filtered off, crystallising the filtrate, and why a titration and a second indicator-free mixing are needed with a soluble base.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Describe how you can tell that enough insoluble solid has been added to an acid when preparing a soluble salt.
Key term
Describe how the excess insoluble solid is removed after it has been reacted with an acid.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Explain why an excess of the insoluble solid is added to the acid when a soluble salt is prepared.
Model answer
The excess makes sure that all of the acid is used up in the reaction.
- 2
Describe how you can tell that enough insoluble solid has been added to an acid when preparing a soluble salt.
Model answer
Solid stops dissolving and settles at the bottom of the mixture.
- 3
Describe how the excess insoluble solid is removed after it has been reacted with an acid.
Model answer
The mixture is filtered, and the excess solid is left as residue in the filter paper.
- 4
Explain why the solution left after filtering off an excess insoluble base contains only salt and water.
Model answer
All the acid has been used up in the reaction and the unreacted solid has been filtered out.
- 5
Explain why leaving unreacted acid in the mixture would spoil a salt prepared this way.
Model answer
The acid would stay in the solution and contaminate the crystals when the water is evaporated.
- 6
Suggest why the acid is warmed before an insoluble base is added to it.
Model answer
Warming makes the solid react and dissolve more quickly.
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