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 compounds and ionic equationsNaming 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 decimetreMoles and the Avogadro constantLimiting reactants and stoichiometry
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 phenolphthaleinHydrogen ion concentration and the pH scaleInvestigating pH change when neutralising an acidDilute and concentrated, weak and strong acidsBases 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 electrodesWriting half equationsOxidation and reduction at the electrodesElectrolysis of copper sulfate solutionInvestigating the electrolysis of copper sulfate
Extracting Metals and Equilibria
Topic overviewInvestigating the reactivity of metalsDisplacement reactions as redox reactionsThe reactivity seriesOres, oxidation and reductionChoosing a method to extract a metalBiological methods of metal extractionCorrosion resistance and recycling metalsLife cycle assessmentReversible reactions and dynamic equilibriumThe Haber process and its conditionsChanging the position of an equilibrium
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
Topic overviewInvestigating the rate of a reactionMeasuring rate and interpreting rate graphsCollision theory and factors affecting rateCatalysts and enzymesExothermic and endothermic changesBond breaking, bond making and the overall energy changeBond energies, activation energy and reaction profiles
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
- 20 subtopics
- 45 things to know
- Paper 3
What Chemical Changes covers
Chemical Changes is examined in Paper 3, Chemistry 1. It covers acids, alkalis and the pH scale, the indicators litmus, methyl orange and phenolphthalein, hydrogen ion concentration and the pH scale, investigating pH change when neutralising an acid, dilute and concentrated, weak and strong acids, bases and alkalis, reactions of acids, and testing for hydrogen and carbon dioxide, neutralisation and its ionic equation, preparing soluble salts from insoluble and soluble reactants, preparing pure, dry copper sulfate crystals, carrying out an acid-alkali titration, solubility rules, predicting precipitates and preparing an insoluble salt, electrolytes and what electrolysis is, movement of ions and predicting the products of molten electrolysis, electrolysis with inert electrodes, writing half equations, oxidation and reduction at the electrodes, electrolysis of copper sulfate solution and investigating the electrolysis of copper sulfate.
Where it is assessed
Paper 3
Chemistry 1: Chemistry in Combined Science: 1 hour 10 minutes, 60 marks, 16.67% of the qualification.
Check the Pearson Edexcel specification ↗The 20 subtopics
Each one has its own page.
- Acids, alkalis and the pH scaleThe hydrogen ions released by acids and hydroxide ions released by alkalis, the ions in sodium hydroxide and sulfuric acid solutions, and the pH values of acidic, neutral and alkaline solutions.Open →
- Indicators: litmus, methyl orange and phenolphthaleinThe colours of litmus, methyl orange and phenolphthalein in acidic and alkaline solutions, and why litmus is less useful than phenolphthalein for finding the exact point of neutralisation.Open →
- Hydrogen ion concentration and the pH scaleHow hydrogen and hydroxide ion concentrations affect pH, the effect of adding water to acidic and alkaline solutions, and the tenfold change in hydrogen ion concentration for each unit change in pH.Open →
- Investigating pH change when neutralising an acidThe apparatus, variables and pH readings when calcium hydroxide is added to hydrochloric acid, how the pH rises and levels off, the equations, why stirring and small additions matter, and presenting the results in tables and graphs.Open →
- Dilute and concentrated, weak and strong acidsConcentrated and dilute solutions and their units, strong and weak acids as fully and partly dissociated, and why a weak acid has a higher pH and reacts more slowly than a strong acid of the same concentration.Open →
- Bases and alkalisWhat bases and alkalis are, metal oxides and hydroxides as bases, why a metal carbonate does not fit the definition of a base, and why every alkali is a base but insoluble bases such as copper oxide are not alkalis.Open →
- Reactions of acids, and testing for hydrogen and carbon dioxideThe products when acids react with metals, metal oxides, hydroxides and carbonates, naming the salts and writing their equations, choosing the acid for a nitrate, and the tests for hydrogen and carbon dioxide.Open →
- Neutralisation and its ionic equationWhat neutralisation is, how the pH changes as alkali is added, the products of neutralising sulfuric acid, how indigestion remedies work, and the ionic equation H⁺ + OH⁻ → H₂O that explains why water always forms.Open →
- Preparing soluble salts from insoluble and soluble reactantsWhy 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.Open →
- Preparing pure, dry copper sulfate crystalsReacting excess copper oxide with warm dilute sulfuric acid, the equation and colour change, filtering off the excess, concentrating over a water bath without evaporating to dryness, and crystallising and drying the crystals.Open →
- Carrying out an acid-alkali titrationUsing a pipette, burette and phenolphthalein, adding acid drop by drop near the end point, concordant results, making a pure salt, and accuracy, precision, repeatability, random and systematic errors and the uncertainty in a mean titre.Open →
- Solubility rulesThe solubility of sodium, potassium and ammonium salts, nitrates, chlorides, sulfates, carbonates and hydroxides, the insoluble exceptions such as silver chloride and barium sulfate, and applying the rules to particular salts.Open →
- Predicting precipitates and preparing an insoluble saltPredicting which mixed solutions give a precipitate, naming silver chloride, barium sulfate, copper hydroxide and lead sulfate, and mixing, filtering, washing and drying an insoluble salt.Open →
- Electrolytes and what electrolysis isWhat an electrolyte is and why molten or dissolved ionic compounds conduct while solids do not, electrolysis as decomposition by electrical energy, why a direct current is used, and the electrodes.Open →
- Movement of ions and predicting the products of molten electrolysisThe cathode and anode, cations and anions and the electrodes they move to, and predicting the metal and non-metal products when molten compounds such as zinc chloride, potassium iodide and aluminium oxide are electrolysed.Open →
- Electrolysis with inert electrodesThe products at each electrode when copper chloride, concentrated sodium chloride and sodium sulfate solutions, acidified water and molten lead bromide are electrolysed, why hydrogen and oxygen form instead of sodium or a sulfur gas, and the tests for chlorine and oxygen.Open →
- Writing half equationsHalf equations for copper, hydrogen, chlorine and oxygen at the electrodes, the electrolysis of molten lead bromide and sodium chloride, and why electrons sit on opposite sides at anode and cathode.Open →
- Oxidation and reduction at the electrodesOxidation and reduction as the loss and gain of electrons, deciding whether chloride, copper and lead ions are oxidised or reduced, why the two always happen together, and why reduction occurs at the cathode and oxidation at the anode.Open →
- Electrolysis of copper sulfate solutionHow the anode loses mass and the cathode gains it when copper sulfate solution is electrolysed with copper electrodes, why the blue colour stays, and purifying copper with an impure anode, a pure cathode and copper sulfate electrolyte.Open →
- Investigating the electrolysis of copper sulfateWhat is seen at graphite electrodes, weighing copper electrodes before and after, how current affects the mass of copper deposited and keeping the comparison fair, hypotheses and predictions, and straight-line graphs, direct proportion and gradients.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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Compare strong and weak acids of the same concentration in terms of hydrogen ion concentration, pH and rate of reaction with magnesium.
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Describe what happens at each electrode when copper is purified by electrolysis of copper sulfate solution with copper electrodes.
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Describe how phenolphthalein appears in acid and in alkali, and what a change to pink shows about a solution.
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Which ion do all acids release when they dissolve in water?
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State the effect on pH of increasing the concentration of hydrogen ions in an acidic solution.
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Name the apparatus used to measure out a fixed volume of dilute hydrochloric acid before calcium hydroxide powder is added to it.
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Define the term base.
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Give the general products formed when an acid reacts with a metal.
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Describe what is meant by a neutralisation reaction.
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Explain why an excess of the insoluble solid is added to the acid when a soluble salt is prepared.
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Name the acid used to prepare copper sulfate crystals from copper oxide.
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Name the apparatus used to measure an accurate fixed volume of alkali into a conical flask for a titration.
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State the solubility in water of nitrates.
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Predict whether a precipitate forms when silver nitrate solution is mixed with sodium chloride solution, and name any precipitate formed.
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Define the term electrolyte.
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Name the product formed at the cathode when copper chloride solution is electrolysed with inert electrodes.
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Write the half equation for the formation of copper at a cathode.
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Define oxidation in terms of electrons.
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Name the two types of electrode that are compared when the electrolysis of copper sulfate solution is investigated.
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Which ion is released into solution when an alkali dissolves in water?
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State the colour of litmus in an acidic solution.
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Two acidic solutions have pH values of 2 and 5. State which contains the greater concentration of hydrogen ions.
Process
State the independent variable when powdered calcium hydroxide is added in stages to a fixed volume of dilute hydrochloric acid.
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Explain what is meant by a concentrated solution.
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Give the two products always formed when a base reacts with an acid.
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Give the general products formed when an acid reacts with a metal oxide.
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State the pH of the solution when an acid has been exactly neutralised by an alkali.
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Describe how you can tell that enough insoluble solid has been added to an acid when preparing a soluble salt.
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Write the balanced equation for the reaction of copper oxide with sulfuric acid.
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Name the apparatus used to add acid a little at a time during a titration.
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Name the two common chlorides that are insoluble in water.
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Predict whether a precipitate forms when barium chloride solution is mixed with sodium sulfate solution, and name any precipitate formed.
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Explain why molten sodium chloride conducts electricity.
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Name the electrode that carries a negative charge during electrolysis.
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Name the product formed at the anode when copper chloride solution is electrolysed with inert electrodes.
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Write the half equation for the formation of hydrogen at a cathode.
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Define reduction in terms of electrons.
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Describe what happens to the mass of the anode when copper sulfate solution is electrolysed using copper electrodes.
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Describe what is seen at the cathode when copper sulfate solution is electrolysed using graphite electrodes.
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Name the ion responsible for the acidic behaviour of a solution of hydrochloric acid.
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State the colour of litmus in an alkaline solution.
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State the effect on pH of increasing the concentration of hydroxide ions in an alkaline solution.
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Name the measurement that is recorded after each addition of calcium hydroxide powder to dilute hydrochloric acid.
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Explain what is meant by a dilute solution.
Take Chemical Changes further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Strong acid vs Weak acid
Strong acid: one whose molecules all dissociate into ions in water. Weak acid: one whose molecules only partly dissociate into ions in water.
Anode vs Cathode
Anode: positive electrode, where negative ions lose electrons. Cathode: negative electrode, where positive ions gain electrons.
Methyl orange vs Phenolphthalein
Methyl orange: indicator that is red in acidic and yellow in alkaline solution. Phenolphthalein: indicator that is colourless in acidic and pink in alkaline solution.
Questions from this topic
Each one with the model answer underneath.
- 1
Which ion do all acids release when they dissolve in water?
Model answer
Acids release hydrogen ions, H⁺, into the solution.
- 2
Which ion is released into solution when an alkali dissolves in water?
Model answer
An alkali releases hydroxide ions, OH⁻, into the solution.
- 3
Name the ion responsible for the acidic behaviour of a solution of hydrochloric acid.
Model answer
The hydrogen ion, H⁺, is responsible for its acidic behaviour.
- 4
Name the two ions formed when sodium hydroxide dissolves in water.
Model answer
It forms sodium ions, Na⁺, and hydroxide ions, OH⁻.
- 5
Explain why hydrogen chloride only behaves as an acid once it has dissolved in water.
Model answer
Only in solution does it release hydrogen ions, and these ions are what make a solution acidic.
- 6
Name the two ions present in an aqueous solution of sulfuric acid.
Model answer
Hydrogen ions, H⁺, and sulfate ions, SO₄²⁻, are present.
What is inside Levo
Six ways to work the same material.
Chemical Changes revision questions
- What does Chemical Changes cover in Edexcel GCSE Combined Science Chemistry?
- 20 subtopics: acids, alkalis and the ph scale, indicators: litmus, methyl orange and phenolphthalein, hydrogen ion concentration and the ph scale, investigating ph change when neutralising an acid, dilute and concentrated, weak and strong acids, bases and alkalis, reactions of acids, and testing for hydrogen and carbon dioxide, neutralisation and its ionic equation, preparing soluble salts from insoluble and soluble reactants, preparing pure, dry copper sulfate crystals, carrying out an acid-alkali titration, solubility rules, predicting precipitates and preparing an insoluble salt, electrolytes and what electrolysis is, movement of ions and predicting the products of molten electrolysis, electrolysis with inert electrodes, writing half equations, oxidation and reduction at the electrodes, electrolysis of copper sulfate solution and investigating the electrolysis of copper sulfate. Each one has its own page with questions and model answers.
- How is Chemical Changes organised?
- By the Edexcel 1SC0 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Chemical Changes, on a schedule.
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