Edexcel GCSE Chemistry

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Formulae, equations and hazards

0.1 - Recalling chemical formulaeLearn to recognise and write common element, compound and ion formulae. You will use the position of numbers, brackets and charges to distinguish formulae that contain similar symbols but represent different substances or particles.
0.2 - Word equationsTurn a description of a reaction into a word equation by separating the starting substances from the substances formed. You will practise keeping complete substance names together and including every reactant and product.
0.3 - Balancing chemical equationsWrite formula equations that conserve atoms, then add state symbols to show whether each substance is solid, liquid, gas or dissolved in water. Worked examples show how coefficients change particle numbers while the formulae stay fixed.
0.4 - Writing ionic equationsHigher tier: use a balanced formula equation to identify the particles that change and cancel unchanged spectator ions. You will check atoms and charge in precipitation and neutralisation equations; knowing common ion formulae and state symbols will help.
0.5 - Recognising chemical hazardsRecognise common pictograms on chemical containers and connect each warning to a suitable laboratory precaution. You will read the actual symbols and explain how a specific action reduces the danger they warn about.
0.6 - Assessing practical risks and precautionsAssess how a practical procedure could cause harm, then choose a precaution that reduces that particular risk. Worked examples link chemical and apparatus hazards to exposure, likelihood and seriousness across a range of practicals.

Topic 1 - Key concepts in chemistry

Atomic structure

1.1 - How atomic models changedDiscoveries of smaller particles changed the atom from Dalton’s indivisible sphere into a model with electrons surrounding a nucleus. You will connect each change to what scientists learned about atomic structure.
1.2 - Inside the atomLearn where protons, neutrons and electrons are found, and how a simple diagram represents their arrangement inside an atom.
1.3 - Charges and masses of subatomic particlesCompare the charges and masses of protons, neutrons and electrons. You will use the relative values correctly without confusing electric charge with mass.
1.4 - Why atoms are electrically neutralAn atom has no overall electrical charge. Learn why this requires equal numbers of protons and electrons, and why their masses and the number of neutrons do not set that balance.
1.5 - The sizes of atoms and nucleiThe nucleus is central but occupies only a tiny part of the atom. Learn to describe that size difference and recognise when a diagram enlarges the nucleus for clarity.
1.6 - Where an atom's mass is concentratedMost of an atom’s mass is concentrated in its tiny nucleus. Use particle masses to explain why occupying more space does not mean containing more mass.
1.7 - Understanding mass numberMass number counts the particles in an atom’s nucleus. Learn which particles to include, how to calculate the total, and what a name such as carbon-12 tells you.
1.8 - Atomic number and element identityAn element’s identity depends on its proton number. Learn to compare atoms using that number, and distinguish it from the total number of particles in the nucleus.
1.9 - IsotopesIsotopes let atoms belong to the same element while having different masses. Learn the two conditions for an isotope pair and use particle counts to identify one.
1.10 - Counting protons, neutrons and electronsUse atomic number and mass number to calculate protons, neutrons and electrons in neutral atoms. Then check a set of particle counts for mistakes.
1.11 - Why relative atomic masses are not always whole numbersA mass number counts particles in one nucleus, whereas relative atomic mass describes an average. Learn how isotope mixtures produce decimal averages without any atom containing a fraction of a neutron.
1.12 - Calculating relative atomic mass from isotopesFor this Higher-tier skill, calculate relative atomic mass as a weighted mean of isotope relative masses. You will use percentage and ratio abundances, then check and round the result.

The periodic table

1.13 - Mendeleev's periodic tableMendeleev used patterns in the properties of elements and their compounds to organise the elements known in his time. You will see how this evidence helped him decide which elements belonged together.
1.14 - Mendeleev's predictionsMendeleev used gaps in a repeating pattern to predict elements that had not yet been discovered. You will follow the reasoning from a gap to a prediction, then see how later discoveries tested it.
1.15 - Isotopes and the order of the periodic tableRelative atomic mass usually increases through the periodic table, but there are exceptions. You will use isotope abundance to explain why an element can have a larger average atomic mass than the element after it.
1.16 - Atomic number and position in the periodic tableAtomic number connects an element’s identity to its place in the periodic table. You will use the proton number of an atom to identify its element and compare positions in the table.
1.17 - Periods, groups and atomic numberThe periodic table uses atomic-number order, horizontal periods and vertical groups. You will use a table extract to recognise these patterns and identify elements likely to have similar chemical properties.
1.18 - Metals and non-metals in the periodic tableAn element’s position gives clues to whether it is a metal or a non-metal. You will connect the broad regions of the periodic table to outer-shell electrons, while recognising the limits of the pattern.
1.19 - Electron arrangements of the first 20 elementsAn electron arrangement shows how an atom’s electrons occupy shells. You will predict arrangements for neutral atoms of the first 20 elements, write them in numbers, and represent them in shell diagrams.
1.20 - Linking electron arrangements to the periodic tableFor the first 20 elements, a neutral atom’s electron arrangement connects to its period and group. You will use occupied shells and outer electrons to find a position, then work backwards from a position to an arrangement.

Ionic bonding

1.21 - Electron transfer and ionic bondingElectron transfer makes positive and negative ions. You will follow this process in sodium chloride and use a dot-and-cross model to distinguish making ions from the attraction that holds them together.
1.22 - Understanding ionsIons can be charged single atoms or charged groups of atoms. You will learn how to read their symbols and distinguish them from neutral atoms and molecules.
1.23 - Counting particles in ionsUse atomic number, mass number and ion charge to count protons, neutrons and electrons. Worked positive- and negative-ion examples show how the electron count changes while the nucleus stays the same.
1.24 - How ions form in ionic compoundsThe outer-shell electrons of Groups 1, 2, 6 and 7 help predict the ions formed in their ionic compounds. You will connect group number, electron transfer and charge, including cases where more than one atom supplies or receives electrons.
1.25 - Naming compounds: -ide and -ateThe endings -ide and -ate give clues about the elements in a compound. You will use familiar ionic compound names to interpret these clues and recognise why oxygen alone does not determine the ending.
1.26 - Writing formulae of ionic compoundsAn ionic compound formula records the simplest ratio of its ions. You will use supplied ion charges to balance positive and negative charge, then use brackets correctly when more than one group ion is needed.
1.27 - The ionic latticeIonic crystals contain a regular arrangement of positive and negative ions. You will connect this three-dimensional structure to the attractions between ions and interpret what a small, flat lattice diagram can show.

Covalent bonding

1.28 - Covalent bonds and shared electron pairsAtoms can join by sharing outer-shell electrons. This lesson explains what a shared pair means and how a diagram represents one covalent bond.
1.29 - How covalent bonds form moleculesCovalent bonds can join atoms into separate particles called molecules. You will distinguish atoms from molecules and recognise molecules of elements and compounds.
1.30 - The sizes of atoms and moleculesAtoms and small molecules are far too small to measure with a classroom ruler. You will learn their approximate scale, convert between metres and nanometres, and use that scale in a simple estimate.
1.31 - Drawing dot-and-cross diagramsA dot-and-cross diagram shows how outer-shell electrons are shared in a molecule. You will build and check diagrams for hydrogen, hydrogen chloride, water, methane, oxygen and carbon dioxide, then explain how sharing completes their outer shells.

Types of substance

1.32 - Classifying structures and bondingElements and compounds can be classified by the type of structure and bonding they have. This classification matters because structure and bonding explain physical properties such as relative melting point, boiling point, solubility in water and electrical conductivity. The best answers do not ju...
1.33 - Properties of ionic compoundsLearn why ionic compounds usually have high melting and boiling points, and why their electrical conductivity changes when they melt or dissolve. The key ideas are strong attractions and mobile ions.
1.34 - Properties of simple molecular substancesLearn how separate molecules explain low melting and boiling points and poor electrical conduction. Distinguish the strong bonds inside a molecule from the weaker forces between molecules.
1.35 - Carbon and giant covalent structuresLearn how graphite and diamond can be different substances while containing the same element, and what their giant covalent classification means.
1.36 - Structures of graphite and diamondCompare how carbon atoms join in diamond and graphite. Learn to read a structure model by counting neighbouring atoms and distinguishing a three-dimensional network from stacked sheets.
1.37 - How structure explains uses of diamond and graphiteUse the bonding in graphite and diamond to explain why graphite works as an electrode and lubricant, while diamond makes an effective cutting edge. Follow each structure → property → use link.
1.38 - Properties of fullerenes, C60 and grapheneCompare a hollow C₆₀ molecule with a one-atom-thick graphene sheet. Use the difference between separate molecules and a continuous network to explain their strength, electrical conduction and response to heating.
1.39 - Simple polymers and poly(ethene)Learn to recognise a simple polymer as very large molecules with carbon chains. Use poly(ethene) to read a short structural fragment and distinguish one bonded chain from a whole sample of polymer.
1.40 - Properties of metalsA copper wire carries current and a metal sheet can be pressed into shape. You will use the structure of a metal to explain both electrical conductivity and malleability, distinguishing electron movement from the sliding of layers.
1.41 - What scientific models can and cannot showChemical models make invisible structures easier to understand. You will compare dot-and-cross diagrams, ball-and-stick models and flat or three-dimensional representations, choosing what each can tell you and recognising what it leaves out.
1.42 - Comparing metals and non-metalsMetals and non-metals show useful patterns in their physical properties, but there are exceptions. You will describe the usual patterns and use several properties together to compare and classify elements.

Calculations involving masses

1.43 - Relative formula mass and percentage by massRelative formula mass is a way of adding up the relative atomic masses of all the atoms shown in a chemical formula. Once you know the relative formula mass, you can calculate what percentage of the compound's mass comes from one element.
1.44 - Empirical formulae from masses and percentagesMass data can be used to work out the formula of a simple compound. The important move is to convert masses, or percentages by mass, into a ratio of atoms. The formula you calculate in this way is an empirical formula: the simplest whole-number ratio of atoms of each element in the compound.
1.45 - Empirical and molecular formulaeEmpirical and molecular formulae both describe the elements in a compound, but they give different levels of detail. The key move is ratio: simplify a molecular formula to the smallest whole-number ratio, or scale an empirical formula up using relative molecular mass.
1.46 - Finding the formula of magnesium oxideAn empirical formula shows the simplest whole-number ratio of atoms of each element in a compound. In this experiment, magnesium is heated so that it reacts with oxygen to form magnesium oxide. The useful evidence is the mass of magnesium that reacted and the mass of oxygen that combined with it.
1.47 - Conservation of mass in closed and open systemsIn a chemical reaction, atoms are rearranged into new substances. The law of conservation of mass says that atoms are not made or destroyed in ordinary chemical reactions, so the total mass is conserved when every substance is included. The important GCSE skill is explaining why the measured mass...
1.48 - Masses from balanced equationsA balanced equation is not just a list of reactants and products. It gives the ratio in which substances react and form. In this Topic 1 calculation skill, you use that ratio with relative formula masses to calculate the mass of one reactant or product when the mass of another substance is given.
1.49 - Calculating mass concentrationA solution can contain a small or large mass of dissolved substance in the same volume. This lesson is about calculating concentration in g dm^-3, which means grams of solute per cubic decimetre of solution. You will convert volume units, calculate concentration and rearrange the relationship to...
1.50 - The mole and the Avogadro constantOne mole is a counting amount used in chemistry. This Higher-tier Topic 1 idea links a measurable mass in grams to a fixed number of particles. The key recall point is that one mole has two equivalent descriptions: it contains the Avogadro constant number of particles, and it has a mass equal to...
1.51 - Moles, particles and mass calculationsThis Higher-tier calculation lesson links the mass you can measure in the lab to the number of particles too small to count directly. The route is always built from two bridges: mass to moles, then moles to particles. Once those bridges are secure, the reverse calculations use the same relationsh...
1.52 - Limiting reactants and mass of productIn many reactions, one reactant is used up before the others. Once that reactant has gone, the reaction cannot keep making product, even if another reactant is still present. In this Higher-tier lesson, you will use mole ratios to find the limiting reactant and calculate the maximum mass of product.
1.53 - Finding reaction ratios from massesIn this Higher-tier lesson, you will turn measured masses into mole ratios and use them to deduce a balanced equation. You will learn how to handle fractional ratios and check that the equation fits both the data and conservation of atoms.

Topic 2 - States of matter and mixtures

States of matter

2.1 - Particle model of solids, liquids and gasesUse the particle model to compare the arrangement, movement and relative energy of solids, liquids and gases. These microscopic differences help explain why a solid keeps its shape, a liquid flows and a gas spreads out.
2.2 - Changes of stateLearn the names and directions of changes of state, distinguish evaporation from boiling, and decide whether an observed change makes a new substance.
2.3 - Explaining changes of state using particlesExplain changes of state by linking energy transfer to particle attractions, arrangement and movement. Distinguish heating a substance within one state from supplying energy while it changes state.
2.4 - Predicting physical state from conditionsUse melting and boiling points to predict a substance’s state at a specified temperature and pressure. Practise comparisons involving negative temperatures, then examine what can and cannot be concluded at an exact change-point.

Methods of separating and purifying substances

2.5 - Pure substances and mixturesWhat does “pure” actually mean? You will distinguish the everyday meaning from chemical purity, then use particles and examples to tell a pure element or compound from a mixture.
2.6 - Using melting points to test purityYou will use the start and end temperatures of melting to judge purity, and distinguish evidence about purity from evidence about a substance’s identity.
2.7 - Separation techniques for mixturesMixtures can be separated using differences in physical properties. You will learn how five separation methods work and which kinds of mixtures each method can separate.
2.8 - Choosing a separation methodYou will choose and describe separation methods from the properties of a mixture. The target product matters: collecting a dissolved solid needs a different method from collecting its solvent.
2.9 - Paper chromatography and phasesYou will explain why soluble substances separate on paper using the mobile and stationary phases, then connect that explanation to the baseline, solvent level and solvent front.
2.10 - Reading chromatograms and calculating RfYou will use spot patterns to investigate purity and identify possible components, then calculate Rf values from measurements made from the baseline.
2.11 - Investigating inks by distillation and chromatographyIn this core practical, you will separate the water and dyes in an ink, carry out both methods safely, and use the results to make supported conclusions about its composition.
2.12 - Drinking water and laboratory waterDrinking water must be safe, while water used in chemical analysis must not introduce dissolved salts. This lesson explains how sedimentation, filtration, chlorination and distillation address different impurities, and how to choose a treatment for its purpose.

Topic 3 - Chemical changes

Acids

3.1 - Acids, alkalis and ionsLearn which ions acids and alkalis supply in water, and how their formulae distinguish ions from neutral atoms or molecules.
3.2 - Understanding the pH scaleUse the pH scale to classify solutions as acidic, neutral or alkaline, including values close to neutral.
3.3 - Using indicatorsLearn the colour changes of litmus, methyl orange and phenolphthalein, then use observations without claiming more than an indicator can show.
3.4 - Hydrogen ion concentration and pHThis Higher-tier lesson connects pH with hydrogen and hydroxide ion concentrations, and explains why the amount of solution is different from its concentration.
3.5 - Tenfold concentration changes and pHIn this Higher-tier lesson, use powers of ten to compare hydrogen ion concentrations and work backwards from a concentration change to a new pH.
3.6 - Investigating neutralisation and pHIn this core practical, add measured portions of calcium hydroxide or calcium oxide to a fixed volume of dilute hydrochloric acid. Learn how to collect pH data, explain the neutralisation curve and improve an estimate of the mass needed to reach neutral.
3.7 - Dilute and concentrated solutionsThis Higher-tier lesson compares solutions using the amount of solute per volume, and explains how dilution changes concentration without removing solute.
3.8 - Weak and strong acidsThis Higher-tier lesson explains acid strength through ionisation, distinguishes it from concentration, and links the two ideas to hydrogen ion concentration and pH.
3.9 - How bases react with acidsUse reactions with acids to recognise bases, explain how water forms, and distinguish the salt-and-water pattern from acid reactions that also release a gas.
3.10 - Alkalis are soluble basesDistinguish bases from alkalis using solubility in water, and use examples to explain why every alkali is a base but not every base is an alkali.
3.11 - Reactions of acidsPredict the products when acids react with metals, metal oxides, hydroxides and carbonates. Use the reactants to name the salt and connect the product pattern to the reacting particles.
3.12 - Tests for hydrogen and carbon dioxideLearn how to distinguish two colourless gases using a chemical test: hydrogen gives a squeaky pop with a lighted splint, while carbon dioxide turns limewater cloudy. You will connect each method to its observation and explain why a flame going out is insufficient evidence.
3.13 - Neutralisation reactions between acids and basesNeutralisation is an acid–base reaction. You will recognise the salt-and-water pattern for metal oxides and hydroxides, name the salt formed, and explain why a mixture can remain acidic after some neutralisation has occurred.
3.14 - The ionic equation for neutralisationIn acid–alkali neutralisation, hydrogen ions and hydroxide ions react to form water. You will write the ionic equation, check its atoms and charge, and distinguish the reacting ions from ions that remain unchanged in solution.
3.15 - Making salts with insoluble reactantsA soluble salt can be made by reacting an acid with an insoluble reactant, then separating the useful salt solution from anything left over. You will connect each separation step to the solubility of the substances present. The important idea is that an insoluble excess solid is easy to remove, w...
3.16 - Making salts with soluble reactantsSome soluble salts are made by neutralising an acid with a soluble reactant, usually an alkali. Because both reactants are dissolved, the method has to avoid leaving any excess acid or alkali in the final solution. The central idea is simple but easy to miss: titration is used to find the correct...
3.17 - Preparing hydrated copper sulfate crystalsThis core practical prepares pure, dry hydrated copper sulfate crystals from copper oxide and dilute sulfuric acid. The chemistry is simple neutralisation, but the practical skill is in choosing the right sequence: warm, react with excess insoluble base, filter, crystallise, and dry. A strong ans...
3.18 - Making a pure salt by titrationWhen an acid reacts with an alkali, neutralisation produces a salt and water. If both reactants are soluble, you cannot add one in excess and filter the excess away, so a titration is used to find volumes that react exactly. You will use the measured volumes to prepare an uncontaminated solution,...
3.19 - Solubility rules for common saltsUse the common solubility rules to decide whether a salt stays dissolved or remains as a solid in water. You will learn the rule groups and exceptions that let you predict precipitation reactions.
3.20 - Predicting precipitates using solubility rulesWhen two clear salt solutions are mixed, sometimes nothing visible happens. At other times, ions from the two solutions form an insoluble solid called a precipitate. This lesson teaches the prediction skill: use the solubility rules to decide whether a precipitate forms, and name the solid if one...
3.21 - Preparing an insoluble salt by precipitationPrepare an insoluble salt by mixing two suitable solutions, then collecting the solid precipitate. You will choose the reactants and explain how filtration, washing and drying give a pure, dry sample.

Electrolytic processes

3.22 - What makes a substance an electrolyte?Learn why molten ionic compounds and their aqueous solutions conduct electricity, while their solids do not. The key is whether charged ions can move.
3.23 - How electrolysis breaks down a compoundLearn how a direct current supply drives a chemical change in an electrolyte, and how this differs from melting or separating a mixture.
3.24 - Ion movement during electrolysisUse ion charges and the connections to a DC supply to explain which way ions move during electrolysis.
3.25 - Predicting electrolysis products with inert electrodesIn electrolysis, the products are the substances formed at the electrodes. This lesson focuses on the five electrolytes named by Pearson Edexcel for this point: copper chloride solution, sodium chloride solution, sodium sulfate solution, water acidified with sulfuric acid, and molten lead bromide...
3.26 - Electrolysis of molten binary compoundsLearn to predict the products from the ions in a molten binary compound. With inert electrodes and no water present, each product comes from an element in the compound.
3.27 - Writing electrode half-equationsHigher tier. Learn to write electrode half-equations by balancing atoms first and then total charge. You will use metal, hydrogen, halogen and oxygen examples.
3.28 - Oxidation and reduction as electron transferHigher tier. Use electron transfer to identify oxidation and reduction, including changes from atoms to ions and from ions to atoms.
3.29 - Oxidation and reduction at the electrodesHigher tier. Connect each electrode to electron transfer: reduction occurs at the cathode and oxidation at the anode. Use that connection to identify an electrode from its reaction.
3.30 - Copper purification by electrolysisElectrolysis transfers copper from an impure anode onto a pure copper cathode. You will link the electrode reactions to the changes in mass and explain why the copper collected is purer than the starting material.
3.31 - Investigating copper sulfate electrolysisThis Pearson Edexcel core practical investigates copper sulfate solution in two ways. With copper electrodes, you measure how the mass of each electrode changes when the current is changed. With inert graphite electrodes, you observe the products formed at the electrodes and explain why they form.

Topic 4 - Extracting metals and equilibria

Obtaining and using metals

4.1 - Comparing the reactivity of metalsMetals do not all react in the same way. Some react quickly with water, some react only with dilute acids, and some can push another metal out of a salt solution. In this lesson, the key skill is to use observations as evidence and deduce a relative order of reactivity.
4.2 - Displacement reactions as redox reactionsExplain metal displacement by following electrons. In this Higher-tier lesson, you will identify which atoms lose electrons, which ions gain them, and why these changes happen together.
4.3 - Reactivity and the formation of metal ionsThe reactivity series puts metals in order from most reactive to least reactive. In this lesson, the evidence comes from reactions with water and dilute acids. The deeper idea is that a more reactive metal atom has a greater tendency to form a positive ion, called a cation.
4.4 - Where metals are foundLearn what an ore is and why most metals occur as compounds, while very unreactive metals such as gold can occur as uncombined elements in the Earth’s crust.
4.5 - Oxidation and reduction involving oxygenTrack oxygen through reactions to identify oxidation and reduction. You will learn to name the substance that changes and explain whether it gains or loses oxygen.
4.6 - Why extracting metals requires reductionUnderstand why extracting a metal from a compound requires reduction. You will distinguish mining and physical separation from the chemical change that produces the metal.
4.7 - Choosing a metal extraction methodUse the reactivity series to decide whether a metal oxide can be reduced with carbon or needs electrolysis. Compare iron and aluminium, and explain why energy cost matters when choosing a method.
4.8 - Biological methods of metal extractionEvaluate bacterial extraction and phytoextraction as ways of obtaining metals from low-grade sources. This Higher-tier lesson explains both routes, why a final chemical step is needed, and how to weigh speed, yield and environmental risks.
4.9 - Resistance to oxidation and the reactivity seriesUse the reactivity series to compare how readily metals are oxidised. You will link position in the series to resistance to oxidation, then distinguish this pattern from the protection provided by an oxide coating.
4.10 - Advantages of recycling metalsRecycling keeps useful metals in circulation and can reduce the need for extraction from ores. You will use evidence about energy, costs, environmental effects and available scrap to judge when recycling is advantageous.
4.11 - Life-cycle assessment stagesA product affects the environment before, during and after its use. You will follow the four stages of a life-cycle assessment and connect each stage to specific resource use, waste or emissions.
4.12 - Evaluating life-cycle assessment dataUse life-cycle assessment data to compare products fairly, calculate comparable totals and make an evidence-based decision. You will distinguish a result for one environmental measure from a conclusion about the whole product.

Reversible reactions and equilibria

4.13 - Understanding reversible reactionsLearn how to recognise a reversible reaction, read its equation in both directions, and use two examples to see how changing conditions can reverse a chemical change.
4.14 - Dynamic equilibriumLearn why an equilibrium mixture can remain unchanged even while its particles keep reacting. You will connect a closed system, equal reaction rates and constant amounts, then interpret rate data.
4.15 - Making ammonia in a reversible reactionAmmonia is made by reacting nitrogen with hydrogen. Learn their industrial sources, balance the formation equation, and apply dynamic equilibrium to this particular reaction.
4.16 - Conditions for the Haber processThe Haber process uses a hot, pressurised reactor and a catalyst to make ammonia. Learn the temperature, pressure and catalyst, with the correct units for each condition.
4.17 - How conditions shift an equilibriumThis Higher-tier lesson develops predictions about how temperature, pressure and concentration change an equilibrium mixture. Use the balanced equation and the energy change to explain which direction is favoured.

Topic 5 - Separate chemistry 1

Transition metals, alloys and corrosion

5.1C - Properties of transition metalsTransition metals include iron, copper and nickel. You will learn their typical physical properties, how their compounds can differ from the metals themselves, and what catalytic activity means.
5.2C - Oxidation of metals and corrosionYou will connect oxidation at a metal surface with corrosion, then distinguish the rusting of iron from corrosion of other metals.
5.3C - Preventing rusting of ironRust prevention works by stopping the reactions that damage iron. You will interpret evidence about the conditions for rusting and compare barrier methods with sacrificial protection.
5.4C - Electroplating to improve metal objectsElectroplating deposits a thin metal coating on an object. You will connect the cell arrangement and electron transfer with improved appearance, lower material cost and resistance to corrosion.
5.5C - Why alloys are often stronger than pure metalsA particle model helps explain why alloying often makes a metal harder to deform. You will compare regular layers in a pure metal with the disturbed arrangement in an alloy, and recognise what this simplified model leaves out.
5.6C - Why iron is alloyed to make alloy steelsDifferent steel compositions suit different jobs. You will use the layer model to explain increased strength and distinguish this from corrosion resistance when choosing an alloy steel.
5.7C - Uses and properties of metals and alloysYou will connect the properties of aluminium, copper and gold with their uses, then explain why alloys such as magnalium, brass and gold alloys can be more suitable for particular jobs.

Quantitative analysis

5.8C - Calculating molar concentrationLearn to calculate concentrations from moles, mass and solution volume, and convert between mol dm⁻³ and g dm⁻³. This separate Chemistry point is Higher tier only.
5.9C - Accurate acid-alkali titrationIn this Edexcel core practical, you carry out an accurate acid-alkali titration using a burette, pipette and a suitable indicator. The aim is to find the volume of one solution needed to exactly neutralise a measured volume of the other solution. Good titration work is careful practical chemistry...
5.10C - Calculating concentrations and volumes from titrationsA titration gives an accurate reacting volume: the volume of one solution needed to exactly react with a fixed volume of another solution. In this lesson, you use those results to calculate either an unknown concentration or an unknown volume required. This separate Chemistry point is Higher tier...
5.11C - Calculating percentage yieldPercentage yield compares the product actually obtained with the calculated maximum. You will choose the correct masses, make their units consistent and calculate or check a percentage yield.
5.12C - Why actual yield is usually lower than theoretical yieldA balanced equation can be used to calculate the maximum amount of a desired product that could be made. In a real experiment, the amount of product collected is usually lower than this calculated maximum. This lesson is about describing why that happens: incomplete reactions, practical losses, a...
5.13C - Understanding atom economyAtom economy describes how much of the reactant mass enters a specified desired product. You will connect this idea to a balanced equation and distinguish it from the amount of product actually collected.
5.14C - Calculating atom economyAtom economy is a percentage that shows how much of the mass in a balanced reaction equation becomes the desired product. A high atom economy means more of the atoms from the reactants are present in the product you wanted. In this lesson, the focus is the calculation: choosing the correct formul...
5.15C - Choosing reaction pathways using dataA specified product can often be made by more than one reaction pathway. This separate Chemistry point is Higher tier only. In separate Chemistry, the exam skill is to use the data you are given to explain why one pathway is chosen. A strong answer does not just spot the biggest number: it links...
5.16C - Molar gas volume at room conditionsThis Higher-tier separate Chemistry lesson connects gas amount and volume at room temperature and pressure. At room temperature and pressure, one mole of molecules of any gas occupies the same volume. In this lesson, that volume is the Edexcel value that will be provided in calculations: 24 dm3 o...
5.17C - Gas volumes and balanced equationsThis Higher-tier separate Chemistry lesson is about using one balanced equation to connect the mass of a solid to the volume of a gas. The calculation route is always the same: convert the known amount into moles, use the balanced equation ratio, then use the molar volume of a gas at room tempera...
5.18C - Gas volume calculations using Avogadro's lawAvogadro's law is useful in this lesson because it links the amount of gas to the volume of gas. When gases are measured at the same temperature and pressure, the balanced equation can be read as a volume ratio for the gases involved. This is a Higher-tier separate Chemistry calculation skill. Th...

The Haber process and fertilisers

5.19C - Ammonia and the reversible Haber reactionLearn how nitrogen and hydrogen form ammonia, how to read the balanced equation, and what its reversible arrow tells you.
5.20C - How quickly equilibrium is reachedHigher tier. Learn how temperature, reacting-particle concentration, gas compression and catalysts affect how quickly equilibrium is approached, while keeping rate separate from equilibrium yield.
5.21C - Choosing industrial equilibrium conditionsHigher tier. Use the Haber process to explain how industry balances equilibrium yield, production rate, raw-material supply and costs when choosing operating conditions.
5.22C - Nitrogen, phosphorus and potassium fertilisersLearn which elements N, P and K represent, why fertilisers supply them as compounds, and how to identify them in a fertiliser mixture.
5.23C - Making ammonium nitrateLearn the reaction that makes ammonium nitrate, explain its name and formula using ions, and connect its nitrogen content to its use as a fertiliser.
5.24C - Making ammonium sulfate in the lab and industryLearn how to prepare ammonium sulfate crystals by titration and crystallisation, then compare this small-scale method with the multi-stage industrial route used to make fertiliser.

Topic 6 - Groups in the periodic table

Group 1 - Alkali metals

6.1 - Recognising Groups 1, 7 and 0Learn to recognise alkali metals, halogens and noble gases from their positions in the periodic table, including why hydrogen is an exception.
6.2 - Physical properties of alkali metalsAlkali metals are soft and melt at relatively low temperatures. Learn what these two physical properties mean and why a low melting point does not necessarily mean a liquid at room temperature.
6.3 - How alkali metals react with waterLithium, sodium and potassium react with cold water to form hydrogen and a metal hydroxide. Learn to describe the observations, write balanced equations and connect demonstration precautions to their hazards.
6.4 - Comparing alkali-metal reactivityUse observations to compare lithium, sodium and potassium, then extend the Group 1 reactivity trend to another alkali metal. Also consider what makes a comparison of demonstrations convincing.
6.5 - Explaining alkali-metal reactivityExplain why alkali metals have similar reactions but become more reactive down Group 1. Connect their electronic configurations to the attraction holding the outer electron in the atom.

Group 7 - Halogens

6.6 - Colours and states of the halogensLearn the colours and physical states of chlorine, bromine and iodine at room temperature, and distinguish the elements from their vapours and ions.
6.7 - Physical property trends in halogensUse the physical-property trends down Group 7 to explain the states of the halogens and predict properties of other members.
6.8 - Chemical test for chlorineLearn how damp litmus paper identifies chlorine gas and why the final bleaching observation matters.
6.9 - Halogen reactions with metalsHalogens react with metals to form metal halides. Learn how to name these products, balance their equations and use the Group 7 reaction pattern.
6.10 - Hydrogen halides and acidic solutionsLearn how halogens form hydrogen halides and why dissolving a hydrogen halide in water produces an acidic solution.
6.11 - Halogen displacement reactionsUse displacement reactions to compare chlorine, bromine and iodine, write equations for successful reactions and predict the behaviour of astatine.
6.12 - Halogen displacement reactions as redoxThis Higher-tier lesson explains electron transfer in the halogen displacement reactions from 6.11. Use ionic and half-equations to identify what is oxidised and what is reduced.
6.13 - Explaining halogen reactivityExplain why halogen reactivity decreases down Group 7 using occupied electron shells, shielding and attraction for an incoming electron.

Topic 7 - Rates of reaction and energy changes

Rates of reaction

7.1 - Measuring rates through gas and colour changesIn this Edexcel core practical, you investigate how changing a condition changes the rate of a chemical reaction. One method measures the volume of carbon dioxide made when hydrochloric acid reacts with marble chips. The other method times the appearance change when sodium thiosulfate reacts with...
7.2 - Choosing methods to measure reaction ratesA rate experiment measures how quickly a reaction changes with time. For this specification point, the skill is to suggest a practical method that matches the reaction: choose a measurable change, record it against time, control the important variables, then use the data to determine a rate. Edex...
7.3 - Reactions occur when particles collideLearn why collisions are necessary for reactions and how collision frequency and energy affect the number of successful reactions each second.
7.4 - Explaining changes in rate using collision theoryReactions can be sped up or slowed down by changing the conditions. Use collision theory to explain the effects of temperature, concentration, gas pressure and solid surface area.
7.5 - Interpreting reaction-rate graphsReaction-rate graphs show how the amount of a reactant or product changes as time passes. In Edexcel Paper 2, this is a data skill: you may need to read axes, calculate a rate from a gradient, recognise when a reaction has finished, or compare two curves. The same graph habits work for mass, volu...
7.6 - Catalysts and reaction rateLearn what distinguishes a catalyst from a reactant, and how rate, product and recovery evidence can support that conclusion.
7.7 - How catalysts lower activation energyUse activation energy to explain why a catalyst can speed up a reaction without raising its temperature.
7.8 - Enzymes in alcoholic-drink productionLearn what an enzyme is and connect biological catalysis to the production of alcoholic drinks.

Heat energy changes in chemical reactions

7.9 - Measuring temperature changes in reactionsDiscover how temperature measurements reveal energy changes when salts dissolve and when neutralisation, displacement or precipitation reactions occur in solution. Learn how to collect comparable measurements and interpret the evidence.
7.10 - Exothermic changes and reactionsLearn what exothermic means and how a temperature rise provides evidence of heat energy moving from a change or reaction to its surroundings.
7.11 - Endothermic changes and reactionsLearn why an endothermic change takes in heat energy while its surroundings can become cooler. Use temperature evidence to distinguish this from an exothermic change.
7.12 - Energy in breaking and forming bondsChemical reactions rearrange atoms by breaking bonds and forming new ones. Learn why these two bond changes transfer energy in opposite directions, and why neither step alone decides the overall energy change.
7.13 - Explaining the overall energy changeUse the energy required to break reactant bonds and the energy released when product bonds form to explain whether a reaction is exothermic or endothermic overall.
7.14 - Energy change from bond energiesHigher tier. Learn to calculate energy changes from a balanced equation and supplied bond energies. Count the bonds, total the energy taken in and released, then subtract and interpret the sign.
7.15 - Activation energyLearn what activation energy means, why a collision may fail to produce a reaction, and how the energy barrier is represented on a reaction profile.
7.16 - Reading and drawing reaction profilesRead, label and draw reaction profiles for exothermic and endothermic reactions. Learn to distinguish activation energy from overall energy change, then practise the drawings in an ungraded notebook activity.

Topic 8 - Fuels and Earth science

Fuels

8.1 - What hydrocarbons containLearn how to recognise a hydrocarbon from its formula and distinguish a compound from a mixture.
8.2 - Crude oil as a mixtureSee why crude oil is a mixture of many molecules, how it is useful, and why its supply is limited.
8.3 - Fractional distillation of crude oilFollow how heating, cooling and different boiling ranges separate crude oil into useful fractions.
8.4 - Uses of crude-oil fractionsLearn the main uses of six fractions obtained from crude oil.
8.5 - How crude-oil fractions differUse hydrocarbon molecule size to explain differences in boiling point, flow and ease of ignition between crude-oil fractions.
8.6 - Homologous seriesRecognise the formula pattern in a homologous series and distinguish changing physical properties from similar chemical behaviour.
8.7 - Complete combustion of hydrocarbon fuelsLearn the products and energy change of complete hydrocarbon combustion, then balance equations by conserving each element.
8.8 - Incomplete combustion of hydrocarbonsExplain how too little oxygen changes hydrocarbon combustion products, and use balanced equations to compare the oxygen needed.
8.9 - Why carbon monoxide is toxicTrace how carbon monoxide interferes with oxygen transport from the lungs to body cells.
8.10 - Incomplete combustion and appliance safetyConnect incomplete combustion in appliances to the different problems caused by carbon monoxide gas and soot particles.
8.11 - How burning fuels produces sulfur dioxideExplain where the atoms in sulfur dioxide come from when a fuel containing sulfur impurities burns.
8.12 - Sulfur dioxide and acid rainFollow how sulfur dioxide contributes to acid rain and why lower pH can damage ecosystems and materials.
8.13 - How engines produce nitrogen oxidesBurning fuel makes an engine hot enough for nitrogen and oxygen from the air to react. This lesson explains how nitrogen oxides form and why this is different from incomplete combustion.
8.14 - Comparing hydrogen and petrol as fuelsCompare hydrogen and petrol by considering emissions, how the fuel is made, storage and safety. You will use those comparisons to make a judgement for a particular driving situation.
8.15 - Fossil fuels and non-renewable resourcesPetrol, kerosene and diesel oil come from crude oil; methane is the main component of natural gas. Learn these sources and explain why the fossil resources supplying them are non-renewable.
8.16 - Cracking long-chain hydrocarbonsCracking changes large hydrocarbon molecules into smaller molecules, including alkenes. Learn how the bonds and products differ, then use atom conservation to complete cracking equations.
8.17 - Why cracking is necessaryFractional distillation does not always supply crude-oil products in the proportions people need. Explain how cracking converts surplus larger hydrocarbons into useful fuels and chemical feedstock.

Earth and atmospheric science

8.18 - Volcanic gases and Earth's early atmosphereDiscover how volcanic activity supplied the gases that formed Earth's early atmosphere, and why lava and ash are different from those gases.
8.19 - Composition of Earth's early atmosphereUse volcanic gases and ancient rocks to understand the model of Earth's early atmosphere. Learn to distinguish observations from the conclusions scientists infer from them.
8.20 - How the oceans formedFollow the sequence from water vapour in the hot early atmosphere to liquid oceans. Use changes of state to explain why cooling mattered.
8.21 - How the oceans removed carbon dioxideExplain how newly formed oceans removed carbon dioxide from the atmosphere, and how some of that carbon could later be stored in rocks.
8.22 - Photosynthesis and rising oxygen levelsLearn how early photosynthetic organisms used carbon dioxide and released oxygen, and why oxygen accumulated in the atmosphere over a long time.
8.23 - Chemical test for oxygenIdentify oxygen using a glowing splint, explain the positive result, and understand what a negative result can and cannot tell you.
8.24 - The greenhouse effectFollow energy from the Sun to Earth's surface and back through the atmosphere. Explain how carbon dioxide, methane and water vapour keep the surface warmer by absorbing and emitting infrared radiation.
8.25 - Evidence linking human activity to climate changeUse climate records to compare fossil-fuel use, carbon dioxide and temperature. Evaluate what the trends show, how measurement uncertainty is handled, and why a causal explanation needs more than matching lines.
8.26 - Today's atmosphere and climate effectsDescribe the main gases in today's atmosphere, connect human activities to carbon dioxide and methane emissions, and compare ways to reduce climate risks with attention to scale and environmental effects.

Topic 9 - Separate chemistry 2

Chemical tests for gases and ions

9.1C - Choosing an identifying test for an ionAn observation identifies an ion only when it distinguishes that ion from the other likely possibilities. You will learn to recognise ambiguous results and choose the extra evidence needed for a valid conclusion.
9.2C - Flame tests for metal ionsLearn how to carry out a flame test on a solid salt, match five characteristic colours to metal ions, and avoid contamination that could lead to a wrong identification.
9.3C - Sodium hydroxide tests for cationsUse sodium hydroxide solution to distinguish the six cations in this topic. You will interpret precipitate colours, test a white precipitate with excess reagent, and identify ammonium ions by the ammonia released on warming.
9.4C - Chemical test for ammoniaLearn the chemical test for ammonia gas and why it uses damp red litmus paper. Then use the apparatus correctly so an alkaline liquid cannot give a misleading result.
9.5C - Tests for carbonate, sulfate and halide ionsLearn the reagent sequence and positive observation for carbonate, sulfate and halide ions. These tests identify negative ions, and using the correct acid prevents the reagent itself from causing a false positive.
9.6C - Identifying ions in unknown saltsThis core practical is about using a logical sequence of qualitative tests to identify the ions in unknown salts. The evidence is mostly observations: flame colours, gases, litmus changes and precipitates. A strong practical answer names the reagent, describes the positive observation, and then d...
9.7C - Interpreting ion-test resultsUse observations from ion tests to identify the cation and anion in a simple unknown salt. You will combine supported results, balance charges when writing a formula, and recognise when the evidence does not justify a definite conclusion.
9.8C - Instrumental methods of analysisInstruments can detect or measure properties of a sample. Learn how they may improve sensitivity, accuracy and speed, and why suitable calibration and clean samples still matter.
9.9C - Flame photometer dataUse known standards to convert a flame photometer reading into a concentration, and use reference signals to identify metal ions. You will distinguish interpolation from extrapolation and judge how strongly the data support a conclusion.

Hydrocarbons

9.10C - Drawing and naming the first four alkanesLearn the names and molecular formulae of the first four alkanes, then use carbon’s four-bond rule to draw and check their displayed structures. This is a separate Chemistry point.
9.11C - Why alkanes are saturatedAlkanes are saturated hydrocarbons. Learn how the elements in a molecule and the bonds between its atoms explain these two words, including the one-carbon example methane. This is a separate Chemistry point.
9.12C - Formulae and structures of alkenesConnect the names ethene, propene, but-1-ene and but-2-ene to their formulae and displayed structures. You will use carbon’s four-bond rule to place hydrogens correctly around a double bond. This is a separate Chemistry point.
9.13C - Why alkenes are unsaturatedExplain why alkenes are unsaturated hydrocarbons and recognise their carbon–carbon double bond. The elements present and the type of bond answer different parts of that description. This is a separate Chemistry point.
9.14C - Addition reaction of ethene with bromineFollow what happens when bromine adds to ethene, then use the same bond changes to predict products from other alkenes. You will track both atom conservation and where each bromine atom attaches. This is a separate Chemistry point.
9.15C - Distinguishing alkanes and alkenesUse bromine water to distinguish an alkane from an alkene, then explain the observations using their bonds. You will also learn why a colour change must be recorded precisely. This is a separate Chemistry point.
9.16C - Complete combustion of alkanes and alkenesExplain why complete combustion oxidises both alkanes and alkenes to carbon dioxide and water. Then practise balancing the equations by tracking carbon, hydrogen and oxygen atoms. This is a separate Chemistry point.

Polymers

9.17C - Polymers and repeating unitsLearn how small repeating units form very large polymer molecules, and why a polymer sample has a high average relative molecular mass.
9.18C - Ethene polymerisation to poly(ethene)Follow ethene molecules as they join into poly(ethene), then learn how a repeating-unit diagram represents the long chain.
9.19C - Addition polymers from monomers with C=C bondsApply the addition-polymerisation pattern to propene, chloroethene and tetrafluoroethene, tracking the groups that remain attached to each repeating unit.
9.20C - Monomers and addition polymersPractise deducing an addition polymer from its monomer and working backwards, while keeping atoms, side groups and continuation bonds consistent.
9.21C - Uses and properties of polymersConnect the properties of four common polymers to their uses, and use product requirements or supplied data to justify a material choice.
9.22C - Polyesters as condensation polymersIn this Higher-tier lesson, explain how diacid and diol monomers form polyester chains and account for the water released at every ester link.
9.23C - Environmental problems caused by polymersExplain the resource and disposal problems associated with polymers: finite feedstocks, persistent landfill waste, combustion gases and sorting before remelting.
9.24C - Evaluating polymer recyclingWeigh the costs, resource savings and environmental effects of polymer recycling, using evidence to reach a judgement for a particular waste stream and product.
9.25C - Natural polymers: DNA, starch and proteinsMatch DNA, starch and proteins to their monomers, and distinguish the number of monomer types from the many units in a polymer molecule.

Alcohols and carboxylic acids

9.26C - Drawing and naming the first four alcoholsLearn the formulae of the first four alcohols and how to draw every bond in their molecules. Here, propanol means propan-1-ol and butanol means butan-1-ol, with the OH group on an end carbon.
9.27C - Alcohols and dehydrationRecognise the alcohol functional group and explain how dehydration turns ethanol into an alkene. Atom counting links the meaning of dehydration to the products.
9.28C - Investigating energy released by alcoholsThis core practical compares the temperature rise produced when four alcohols burn: ethanol, propanol, butanol and pentanol. The alcohol is burned in a spirit burner, and the heat released is used to warm a known mass of water. You will plan a fair comparison, process measurements per gram of fue...
9.29C - Formulae and structures of carboxylic acidsUse carbon-count prefixes to learn the first four carboxylic acids. Build their displayed structures by showing the complete acid group and checking every atom’s bonds.
9.30C - The carboxyl group and acidityConnect the carboxyl group to hydrogen ions in water, then use familiar acid reaction patterns to predict what carboxylic acids do.
9.31C - Ethanol oxidation to ethanoic acidEthanol can be oxidised to ethanoic acid. Learn what changes in the molecule and use the same carbon-chain pattern to predict products from the other alcohols studied here.
9.32C - Using homologous series to predict reactionsUse a known reaction to predict what another member of the same homologous series will do. The functional group determines the reaction pattern; the carbon chain determines the particular product.
9.33C - Production of ethanol by fermentationExplain how yeast converts glucose into ethanol, why the conditions matter and how a water seal lets carbon dioxide escape while limiting air entry. Fermentation produces ethanol mixed with water.
9.34C - Concentrating ethanol by fractional distillationUse boiling-point differences and repeated evaporation and condensation to separate an ethanol-rich liquid from a fermentation mixture. Understand what the column, thermometer and condenser each do.

Materials and nanoparticles

9.35C - The size of nanoparticlesLearn how nanoparticles compare in size with atoms and simple molecules, how to convert nanometres into metres, and how to calculate a diameter ratio.
9.36C - Nanoparticle properties and usesExplore why small particle size can change a material’s properties. Use surface-area calculations to explain catalysts, then link the light behaviour of metal oxide nanoparticles to sunscreens.
9.37C - Evaluating nanoparticle risksExplain why some nanoparticulate materials may pose risks, how exposure affects those risks, and how evidence can support a balanced decision about a proposed use.
9.38C - Comparing ceramics, polymers, composites and metalsCompare glass, clay ceramics, polymers, composites and metals using precise property descriptions and supplied data. Learn why strength, hardness and toughness mean different things, and when a comparison needs more evidence.
9.39C - Choosing materials using evidenceUse property data to select materials for a particular job. Check essential limits first, then justify your choice by comparing performance, mass and cost, including any trade-off.