Chemistry

States of Matter and Their Properties Matter exists in three states: solid , liquid , and gas . The physical form a substance takes depends on the separation,…

Elements, Compounds and Mixtures All matter can be classified as either a pure substance (an element or a compound) or a mixture . Element: a substance made of…

The Structure of the Atom An atom has a small, dense nucleus containing protons and neutrons, surrounded by electrons arranged in shells. Particle Location…

Forming Ions Atoms can gain or lose electrons to become charged particles called ions , achieving a stable, full outer shell like the nearest noble gas. Cation…

What is a Covalent Bond? A covalent bond forms when a pair of electrons is shared between two atoms, so that both atoms gain a stable, noble-gas electronic…

What is a Chemical Formula? A chemical formula is a representation of a substance using chemical symbols and numbers, showing which elements are present and how…

What is Electrolysis? Electrolysis is the decomposition of an ionic compound, molten or in aqueous solution, by the passage of an electric current through it.…

Exothermic Reactions All chemical reactions involve energy changes. In an exothermic reaction, thermal energy is transferred to the surroundings, so the…

Physical Changes A physical change is a change in which no new substance is formed - only the physical appearance or state changes. No new substances are formed…

What is Rate of Reaction? The rate of reaction is how quickly reactants are converted into products. rate of reaction = (amount of reactant used (or product…

What is a Redox Reaction? A redox reaction is a reaction involving oxidation and reduction happening simultaneously - the term combines "reduction" and…

Acids and Bases Acids release hydrogen ions (H⁺) in water and have a pH less than 7. Common acids: hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid…

Acidic and Basic Oxides Oxides are classified according to their metallic or non-metallic character: Oxide type Element type Reacts with Examples Acidic oxide…

Naming Salts A salt is formed when the H⁺ ions of an acid are replaced by metal or ammonium ions. Acid Salt ending Example Hydrochloric acid -chloride sodium…

Periods and Groups The Periodic Table arranges all known elements in order of increasing proton number (atomic number) , in horizontal periods and vertical…

The Alkali Metals: Lithium, Sodium, Potassium Group I contains the alkali metals . The syllabus focuses on the first three: lithium (Li), sodium (Na) and…

The Halogens: Chlorine, Bromine, Iodine Group VII contains the halogens . The syllabus focuses on chlorine (Cl), bromine (Br) and iodine (I) - reactive diatomic…

Properties of Transition Elements Transition elements occupy the central block of the Periodic Table (e.g. Sc to Zn, including iron, copper, and platinum). As…

Group VIII: Unreactive, Monatomic Gases The noble gases (Group VIII/0: helium, neon, argon, krypton, xenon, radon) are unreactive and exist as single, separate…

Physical Properties: Metals vs. Non-Metals Metals share a set of characteristic physical properties, all traceable to the same cause: a metal is a lattice of…

Linking Physical Properties to Uses Every use of a metal in this topic must be justified by naming the specific physical property/properties that make it…

What Is an Alloy? An alloy is a mixture of a metal with one or more other elements (usually other metals, sometimes carbon - a non-metal). Alloy Composition…

The Order of Reactivity The reactivity series lists metals in order of how readily they react - from most reactive (top) to least reactive (bottom). Two…

Conditions Required for Rusting Rusting is the corrosion of iron and steel to form hydrated iron(III) oxide , Fe₂O₃·xH₂O - a flaky, brown/orange solid. Rusting…

Ease of Extraction Depends on Reactivity Most metals are found in the Earth's crust combined with other elements, as an ore - a rock from which a metal can be…

Chemical Tests for the Presence of Water Two anhydrous salts change colour when water is added to them, so they are used as simple chemical tests for the…

Composition of Clean, Dry Air Gas Approximate percentage Nitrogen, N₂ 78% Oxygen, O₂ 21% Noble gases (mainly argon) and carbon dioxide, CO₂ remainder (~1%)…

Saturated and Unsaturated Compounds A saturated compound has molecules in which all the carbon-carbon bonds are single bonds Alkanes are the saturated…

Fossil Fuels and Petroleum The fossil fuels are coal , natural gas and petroleum . Methane is the main constituent of natural gas. A hydrocarbon is a compound…

Alkanes The bonding in alkanes is single covalent throughout, so alkanes are saturated hydrocarbons . Name Molecular formula Structural formula Methane CH₄ CH₄…

Alkenes The bonding in alkenes includes a double carbon-carbon covalent bond (C=C), so alkenes are unsaturated hydrocarbons . Name Molecular formula Structural…

Polymers and Monomers A polymer is a large molecule built up from many smaller molecules called monomers , joined together in a long chain. Plastics are…

Apparatus for Measurement Different pieces of apparatus are used to measure time, temperature, mass and volume: Measurement Apparatus Time Stop-watch…

What is Paper Chromatography? Paper chromatography is used to separate a mixture of soluble, coloured substances (such as the dyes in ink) using a suitable…

Choosing a Method Which separation or purification technique is suitable depends on the properties of the substances in the mixture - whether they are soluble,…

Tests for Anions An anion is a negatively charged ion. Each anion below is identified by a specific chemical test. Anion Test Positive Result Carbonate, CO₃²⁻…