Edexcel IGCSE Chemistry

Last Accessed

Recently visited lessons will appear here for quick access.Start exploring your first lesson today!

Principles of chemistry

The Periodic Table

1.18-1.19, 1.22 - Periodic table arrangement and electron configurationsThe Periodic Table is not just a list of elements. Its rows and columns give clues about atomic number and electron arrangement. In this lesson, you will learn how to use an element's position to deduce its electronic configuration for the first 20 elements.
1.20-1.21 - Metals and non-metalsChemists often begin by asking a simple classification question: is this element a metal or a non-metal? In this lesson, you will use three kinds of evidence: where the element sits in the Periodic Table, whether the element conducts electricity, and whether its oxide behaves as acidic or basic.
1.23-1.24 - Group trends and noble gasesThe Periodic Table is not just a list of elements: it puts elements with related electron arrangements into the same vertical groups. This lesson explains why elements in the same group often react in similar ways, and why the noble gases in Group 0 are different because their outer shells are al...

Chemical formulae, equations and calculations

1.25-1.26 - Writing equations and calculating formula massesChemical equations are a compact way to show what changes during a reaction. This lesson teaches how to move from words to balanced chemical equations with state symbols, and how to calculate relative formula mass, Mr, from relative atomic masses, Ar. The same careful counting links both skills:...
1.27-1.30 - Moles, reacting masses and percentage yieldChemists cannot count atoms or ions one by one, so they use a counting unit called the mole. In this lesson, you will use masses, relative atomic masses, relative formula masses and balanced equations to work out how much substance reacts or forms. You will then compare the maximum possible produ...
1.31-1.33 - Empirical and molecular formulae from dataA chemical formula tells you the ratio of atoms or ions in a substance. This lesson shows how experimental mass data can be turned into that ratio, and how an empirical formula can be scaled up to a molecular formula when the Mr is known. The central move is always the same: change masses into mo...
1.34C-1.35C - Concentration and gas volume calculationsChemists often measure a volume in the lab, but balanced equations compare amounts of substance in moles. In this lesson, the same idea appears twice: a solution volume can be linked to concentration, and a gas volume can be linked to the molar volume of a gas at room temperature and pressure. Th...
1.36 - Formula of a metal oxide practicalA metal oxide contains a metal chemically combined with oxygen. In this practical, the formula is found from mass measurements: either oxygen is added to a metal by combustion, or oxygen is removed from a metal oxide by reduction. The skill is not just doing the heating; it is using the mass chan...

Covalent bonding

1.44-1.46 - Covalent bonding and dot-and-cross diagramsCovalent bonding happens when atoms share electrons. In this lesson, you will learn exactly what a covalent bond is, how Pearson describes the electrostatic attraction in the bond, and how to represent the bonding using dot-and-cross diagrams for the molecules named in the specification.
1.47-1.48 - Simple molecular substancesSimple molecular substances are made from separate molecules. The covalent bonds inside each molecule are strong, but the forces between neighbouring molecules are much weaker. That difference explains why many simple molecular substances are gases or liquids, and why the ones that are solids usu...
1.49-1.51 - Giant covalent structuresSome covalent substances are made from small molecules. Others are different: their atoms are joined in a huge network of covalent bonds. Giant covalent structures explain why diamond is extremely hard, why graphite can write on paper and conduct electricity, and why C60 fullerene behaves differe...

Inorganic chemistry

Acids, alkalis and titrations

2.28-2.30 - Acids, alkalis and indicatorsMany acidic and alkaline solutions are colourless, so you often need an indicator to tell what type of solution you have. This lesson focuses on three named indicators, the pH scale from 0 to 14, and how universal indicator gives an approximate pH. Keep the job of each test clear: some indicators...
2.31-2.32 - Ions in acids - alkalis and neutralisationAcids and alkalis are not only identified by indicator colours or pH values. In water, their behaviour can be explained using ions: acids are sources of hydrogen ions, and alkalis are sources of hydroxide ions. Neutralisation happens because the ions from an alkali can remove the acidic effect of...
2.33C - Acid-alkali titrationAn acid-alkali titration is a practical method for finding the volume of one solution needed to exactly neutralise a measured volume of another solution. One solution is measured accurately into a conical flask, and the other is added from a burette until an indicator shows the endpoint. Pearson...

Acids, bases and salt preparations

2.34-2.36 - Solubility rules and proton transferSome ionic compounds dissolve in water and some do not. Edexcel expects you to use a short set of solubility rules to predict whether a common ionic compound is soluble, and to understand acid-base reactions as transfers of protons. These two ideas sit together because many reactions in this topi...
2.37-2.38 - Acid reactions and basesAcids make salts in several predictable ways. This lesson keeps the patterns separate: acids can react with metals, bases and metal carbonates, but the products are not always the same. The acid helps decide the salt ending, while the metal or ammonium part supplies the first part of the salt name.
2.39-2.40C, 2.42 - Preparing soluble saltsMany salts dissolve in water, so making a pure, dry solid sample is not as simple as filtering out a precipitate. In this lesson, the key skill is choosing the right reactants, making a salt solution without excess reactants, then using crystallisation to obtain crystals. The named Pearson practi...
2.41C, 2.43C - Preparing insoluble saltsSome salts do not dissolve in water, so they cannot be made by crystallising a solution. Instead, you make them by mixing two soluble reactants so the ions meet and form an insoluble solid called a precipitate. This lesson focuses on the practical method for making a pure, dry sample of an insolu...

Chemical tests

2.44 - Gas testsSome reactions make gases, and the gas is often the evidence that tells you what happened. In this lesson, the job is to describe the positive tests for five named gases: hydrogen, oxygen, carbon dioxide, ammonia and chlorine. A strong Edexcel answer normally gives both the test method and the po...
2.45-2.47 - Flame tests and cation testsCations are positive ions. In this lesson, you identify some cations by carrying out practical tests and matching the observations to known results. The key exam skill is to describe the test clearly, give the observation, and use that observation to identify the ion.
2.48-2.50 - Anion and water testsMany ionic compounds look similar as colourless solutions or white solids, so chemists use chemical tests that give visible evidence. In this lesson, the evidence is a precipitate, a gas test, a colour change in anhydrous copper(II) sulfate, or a fixed physical property of pure water. The exam sk...

Physical chemistry

Energetics

3.1-3.4 - Exothermic - endothermic reactions and calorimetryChemical reactions can transfer heat energy to or from their surroundings. Calorimetry is the set of simple experiments that measure this transfer using a temperature change. In this lesson, the thermometer reading becomes useful data: it tells you whether a reaction is exothermic or endothermic,...
3.5C-3.7C - Energy profiles, bonds and enthalpy from bond energiesEnergy changes in reactions can be shown in two connected ways: on an energy profile diagram, and by calculating the energy needed to break and make bonds. This lesson focuses on the separate-science extension: drawing and explaining exothermic and endothermic energy level diagrams, then using bo...
3.8 - Temperature-change practicalsTemperature-change practicals are about collecting trustworthy temperature data during a chemical or physical change. In this lesson, you will use the right apparatus, choose fair controls, read maximum or minimum temperatures, and explain the main sources of error for dissolving, neutralisation,...

Rates of reaction

3.9-3.11 - Rate experiments and collision theoryRates of reaction tell you how fast reactants are used up or products are made. In this lesson, you will learn how to investigate rate using measurable changes, how common changes affect rate, and how to explain those effects using particle collision theory.
3.12-3.14C - Catalysts and reaction profilesA catalyst is a way to make a reaction faster without changing the overall chemical reaction. In this lesson, you will learn the exact catalyst wording Pearson expects, then connect it to reaction profile diagrams. The key diagram idea is simple but powerful: a catalyst changes the pathway and th...
3.15-3.16 - Rate practicals - marble chips and hydrogen peroxideRate practicals turn a reaction into measurements taken over time. In this lesson, the focus is on two Pearson Edexcel IGCSE Chemistry practicals: marble chips reacting with dilute hydrochloric acid, and hydrogen peroxide decomposing with different solid catalysts. The exam skill is to describe a...

Organic chemistry

Crude oil

4.7-4.10 - Crude oil fractions and fractional distillationCrude oil is useful because it is not one substance. It is a mixture of many hydrocarbons that can be separated into groups called fractions. In this lesson, you will learn how industrial fractional distillation separates crude oil, then remember the main fractions, their uses, and the trends in...
4.11-4.13 - Complete and incomplete combustionHydrocarbon fuels are useful because burning them transfers energy to the surroundings as heat. The products formed depend on how much oxygen is available. In this lesson, the key comparison is complete combustion in plenty of oxygen versus incomplete combustion when the oxygen supply is limited.
4.14-4.16 - Pollutants and acid rainHydrocarbon fuels are useful because they release energy when they burn. Real fuels and real engines also produce small amounts of other gases that can harm the environment. This lesson follows the two pollutant routes in this cluster: oxides of nitrogen from hot car engines, and sulfur dioxide f...
4.17-4.18 - Cracking and demand for fractionsFractional distillation separates crude oil into fractions, but it does not automatically give refiners the amounts people want. Catalytic cracking is the chemical process that turns some surplus long-chain alkanes into shorter-chain alkanes and alkenes. In this lesson, you will learn the require...