Chemistry
IGCSE · 35 topics available
Chapter 1 · States of Matter
States of Matter
The three states of matter — solid, liquid and gas — explained by particle arrangement, movement and energy, and the changes between them.
OpenDiffusion
Diffusion is the net movement of particles from high to low concentration; it is faster in gases, at higher temperature and for lighter molecules.
OpenChapter 2 · Atoms, Elements and Compounds
Elements, Compounds and Mixtures
How to classify substances as elements, compounds or mixtures, and how their bonding, composition and separation differ.
OpenAtomic Structure and Isotopes
The particles inside an atom, how proton and nucleon numbers describe it, isotopes, and calculating relative atomic mass.
OpenIons and Ionic Bonds
How metals and non-metals transfer electrons to form ions, the ionic bond, giant lattices and the properties of ionic compounds.
OpenSimple Molecules and Covalent Bonds
How non-metal atoms share electrons to form covalent bonds and simple molecules, and why these substances have low melting points.
OpenMetallic Bonding
How a lattice of positive metal ions held together by a sea of delocalised electrons explains typical metallic properties.
OpenChapter 3 · Stoichiometry
Chemical Formulae and Equations
How to write formulae using valencies/ionic charges and how to balance symbol equations so atoms are conserved.
OpenThe Mole and Avogadro Constant
The mole is the chemist's counting unit; it links number of particles, mass and (for gases) volume.
OpenReacting Masses
Using mole ratios from balanced equations to calculate the masses of reactants and products.
OpenConcentration and Empirical Formulae
Working out the concentration of a solution and finding the simplest whole-number ratio of atoms in a compound.
OpenChapter 4 · Electrochemistry
Chapter 5 · Exothermic and Endothermic Reactions
Chapter 6 · Chemical Reactions
Rate of Reaction
Rate of reaction measures how fast reactants form products; it increases with temperature, concentration, surface area and catalysts.
OpenReversible Reactions and Equilibrium
Reversible reactions go both ways; at dynamic equilibrium in a closed system the forward and backward rates are equal.
OpenRedox Reactions
In redox reactions oxidation (loss of electrons) and reduction (gain of electrons) happen together — remember OIL RIG.
OpenChapter 7 · Acids, Bases and Salts
Acids and Bases
Acids produce H⁺ ions in water; bases neutralise acids; soluble bases (alkalis) give OH⁻. The pH scale measures acidity.
OpenOxides
Oxides classified as basic, acidic, amphoteric or neutral by how they react with acids and bases.
OpenPreparation of Salts
Methods for making soluble and insoluble salts using solubility rules, excess reactant, titration and precipitation.
OpenChapter 8 · The Periodic Table
Arrangement of the Periodic Table
Elements ordered by proton number; groups share outer electrons and properties, periods share the number of electron shells.
OpenGroup I and Group VII Elements
Alkali metals (reactivity rising down the group) and halogens (reactivity falling down the group), with trends and displacement.
OpenTransition Elements and Noble Gases
Transition metals: coloured compounds, variable oxidation states, catalysts. Noble gases: full outer shell, inert, monatomic.
OpenChapter 9 · Metals
Properties and Reactivity of Metals
Physical properties of metals and the reactivity series, used to predict reactions with water and acids and displacement.
OpenExtraction of Metals
How the reactivity series decides whether a metal is extracted by carbon reduction, by electrolysis, or found native.
OpenCorrosion of Metals
Why iron rusts when water and oxygen are present, and how barrier, galvanising and sacrificial methods prevent it.
OpenChapter 10 · Chemistry of the Environment
Chapter 11 · Organic Chemistry
Fuels and Alkanes
Fossil fuels, the saturated alkane series (CnH2n+2), their combustion, and substitution reactions with halogens.
OpenAlkenes
Unsaturated hydrocarbons with a C=C bond (CnH2n): the bromine-water test, addition reactions, cracking and polymerisation.
OpenAlcohols
Alcohols contain the -OH group; meet ethanol, how it is made by fermentation and hydration, and its combustion and oxidation.
OpenCarboxylic Acids
Carboxylic acids contain -COOH and are weak acids; see how ethanoic acid reacts with metals, carbonates, alkalis and alcohols.
OpenPolymers
Monomers join to form polymers by addition (C=C, no by-product) or condensation (releasing water), e.g. poly(ethene), nylon and Terylene.
OpenChapter 12 · Experimental Techniques and Chemical Analysis
Separation and Purification
Filtration, crystallisation, distillation and chromatography separate mixtures; a pure substance melts sharply, and Rᶠ identifies a spot.
OpenIdentification of Ions and Gases
Flame tests and NaOH identify cations; silver nitrate, barium chloride and acid identify anions; gas tests use limewater, splints and litmus.
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