Definitions Portal
Search or browse exam-ready definitions by topic. The equilibrium constant for the ionisation of an acid in aqueous solution. A weak acid or weak base whose acid and conjugate-base forms have different colours and whose colour depends on pH. An oxide that reacts with bases and may form an acid with water. The number of protons that one formula unit or molecule of a base can accept. The minimum energy that colliding particles must possess for a reaction to occur. A carboxylic acid derivative containing the –COCl functional group. Polymerisation in which unsaturated monomers join without elimination of a small molecule. A reaction in which two reactants combine to form a single product, often by addition across a multiple bond. An organic compound containing a hydroxyl group bonded to a saturated carbon atom. An organic compound containing a terminal carbonyl group in which the carbonyl carbon is bonded to at least one hydrogen. A saturated hydrocarbon containing only carbon-carbon single bonds. An unsaturated hydrocarbon containing at least one carbon-carbon double bond. An unsaturated hydrocarbon containing at least one carbon-carbon triple bond. A helium-4 nucleus containing two protons and two neutrons. A carboxylic acid derivative containing a carbonyl group bonded to nitrogen. An organic derivative of ammonia in which one or more hydrogen atoms have been replaced by alkyl or aryl groups. An oxide that reacts with both acids and bases. A species capable of behaving as either an acid or a base. The electrode at which oxidation occurs. An aromatic hydrocarbon containing one or more benzene-type rings. A substance that increases the concentration of hydrogen or hydronium ions when dissolved in water. A substance that increases the concentration of hydroxide ions when dissolved in water. The smallest particle of an element that retains the chemical properties of that element. A measure of atomic size, commonly taken as half the distance between the nuclei of two bonded identical atoms. Catalysis of a reaction by one of its own products. The number of specified particles in one mole, approximately 6.022 × 10²³ mol⁻¹. A liquid mixture that boils at constant composition because the vapour has the same composition as the liquid. A titration in which a known excess of reagent is added to the analyte and the unreacted excess is then determined by titration. The equilibrium constant for the reaction of a weak base with water. The most intense peak in a mass spectrum, assigned a relative intensity of 100%. An oxide that reacts with acids to form a salt and water. The number of protons that one molecule of an acid can donate in its acid-base reactions. A high-speed electron emitted from the nucleus during beta-minus decay. A ligand that forms two coordinate bonds to a central metal ion. The enthalpy change required to break one mole of a specified covalent bond in gaseous molecules. Unequal distribution of bonding electron density caused by a difference in electronegativity between bonded atoms. A Hess’s-law cycle that relates lattice enthalpy to other enthalpy changes involved in forming an ionic compound. A proton donor. A proton acceptor. A solution that resists changes in pH when small amounts of acid or alkali are added. A positively charged carbon-containing species in which the positive charge is associated with a carbon atom. An organic compound containing the carboxyl group, –COOH. A substance that increases the rate of a reaction by providing an alternative pathway with lower activation energy and is regenerated overall. Reduction or destruction of catalytic activity caused by a substance binding strongly to active sites on the catalyst. The ability of an element to form covalent bonds with itself, producing chains, rings or networks. The electrode at which reduction occurs. Structural isomerism caused by different arrangements of the carbon skeleton. A complex containing a multidentate ligand bonded to the same central metal ion through two or more donor atoms. The enhanced stability commonly shown by complexes containing multidentate ligands compared with analogous complexes containing comparable monodentate ligands. The position of an NMR signal relative to a reference standard, usually TMS, expressed in ppm. An atom, usually carbon, bonded to four different groups and capable of giving rise to enantiomerism. A molecule that is not superimposable on its mirror image and, in the syllabus context, does not possess a plane of symmetry. A separation technique based on different distributions of substances between a stationary phase and a mobile phase. A property of a dilute solution that depends on the number of dissolved particles rather than their chemical identity. The shift in an ionic equilibrium caused by adding an electrolyte containing an ion already present in that equilibrium. A species consisting of a central metal atom or ion bonded to ligands by coordinate bonds. A charged species consisting of a central metal ion bonded to surrounding ligands by coordinate bonds. A redox reaction in which two species containing the same element in different oxidation states form a product with an intermediate oxidation state. Polymerisation in which monomers join with elimination of a small molecule such as water or hydrogen chloride. A reaction in which two molecules join with elimination of a small molecule such as water. Stereoisomerism arising from different spatial arrangements accessible by rotation about single bonds without breaking covalent bonds. The species formed when a base accepts a proton. Two species that differ by one proton. The species formed when an acid donates a proton. A system containing adjacent atoms with overlapping p orbitals that allow electron delocalisation. The number of coordinate bonds formed between ligands and the central metal ion. The deterioration of a metal through chemical or electrochemical reaction with its environment. The electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms. The highest temperature at which a substance can exist as a liquid, regardless of pressure. The total pressure of a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases. A covalent bond in which both electrons in the shared pair are supplied by the same atom. The fraction of the initial amount of a substance that has dissociated at equilibrium. Spreading of electron density over three or more adjacent atoms rather than localisation between two atoms. Electrons that are spread over more than two atoms rather than being confined to a single bond. An organic ion containing the diazonium group, –N₂⁺, bonded to carbon. An intermolecular attraction between permanent dipoles of polar molecules. A reaction in which a more reactive element replaces a less reactive element from one of its compounds. A representation showing all atoms and all covalent bonds in a molecule. A redox reaction in which the same species is simultaneously oxidised and reduced. A redox reaction in which the same species is simultaneously oxidised and reduced. A state in a closed system in which the forward and reverse reactions occur at equal rates, so macroscopic properties remain constant. An arrangement of redox couples according to their standard electrode potentials. The potential difference associated with a half-cell, reflecting its tendency to undergo reduction relative to another half-cell. The chemical decomposition of an electrolyte by the passage of an electric current. The enthalpy change when one mole of gaseous atoms each gains one electron to form one mole of gaseous 1− ions. The ability of an atom in a covalent bond to attract the bonding pair of electrons towards itself. An electron-pair acceptor. An addition reaction in which an electrophile attacks an electron-rich multiple bond. A substitution reaction in which an electrophile replaces an atom or group attached to an aromatic ring. A substitution reaction in which an electrophile replaces an atom or group, particularly on an aromatic ring. A single molecular event in a reaction mechanism. A reaction in which atoms or groups are removed from adjacent atoms to form a multiple bond. The simplest whole-number ratio of atoms of each element in a compound. A pair of non-superimposable mirror-image stereoisomers. The observed point in a titration at which an indicator changes colour. A process that absorbs heat from the surroundings; its enthalpy change is positive. The heat energy change of a reaction at constant pressure. A measure of the dispersal of energy and matter in a system. The equilibrium constant expressed in terms of equilibrium concentrations, each raised to the power of its stoichiometric coefficient. The equilibrium constant expressed in terms of equilibrium partial pressures of gaseous species, each raised to the power of its stoichiometric coefficient. The point in a titration at which reactants have been mixed in the exact stoichiometric proportions required by the reaction. A carboxylic acid derivative containing the –COOR functional group. A condensation reaction in which a carboxylic acid reacts with an alcohol to form an ester and water. An organic compound containing an oxygen atom bonded to two carbon groups, R–O–R′. A state in which one or more electrons occupy higher-energy levels than in the ground state. A process that transfers heat from the system to the surroundings; its enthalpy change is negative. The charge carried by one mole of electrons, approximately 9.65 × 10⁴ C mol⁻¹. Separation of an insoluble solid from a fluid by passing the mixture through a porous barrier. The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions. A qualitative test in which characteristic light emitted by excited atoms or ions in a flame is used to help identify certain elements. Separation of miscible liquids by repeated vaporisation and condensation in a fractionating column. An ion formed by fragmentation of a molecular ion or another ion in a mass spectrometer. A species containing an unpaired electron. A substitution reaction involving free radicals, typically proceeding through initiation, propagation and termination steps. An electrochemical cell that converts the chemical energy of continuously supplied fuel and oxidant directly into electrical energy. An atom or group of atoms responsible for the characteristic chemical reactions of an organic compound. Structural isomerism in which compounds with the same molecular formula contain different functional groups. An electrochemical cell in which a spontaneous redox reaction produces electrical energy. High-energy electromagnetic radiation emitted from an unstable nucleus. Stereoisomerism caused by restricted rotation, giving different spatial arrangements such as cis and trans forms. A continuous network of atoms joined by covalent bonds. A three-dimensional arrangement of oppositely charged ions held together by electrostatic attractions. A thermodynamic quantity defined by ΔG = ΔH − TΔS that indicates whether a process is thermodynamically feasible under specified conditions. The lowest-energy electronic state of an atom, ion or molecule. A system containing an oxidation-reduction couple in contact with an electrode. The time required for the number of undecayed radioactive nuclei, or the activity of a radioactive sample, to fall to half its initial value. An organic compound in which a halogen atom is bonded to an sp³ carbon of an alkyl group. An aromatic compound in which a halogen atom is bonded directly to an aromatic ring. The enthalpy change of a reaction is independent of the route taken, provided the initial and final states are the same. A catalyst in a different phase from the reactants. An equilibrium in which reactants and products occur in more than one phase. Breaking a covalent bond so that both electrons from the bonding pair go to the same atom. A catalyst in the same phase as the reactants. An equilibrium in which all reactants and products are in the same phase. A family of organic compounds with the same functional group and general formula, similar chemical properties, and successive members differing by CH₂. Breaking a covalent bond so that one electron from the bonding pair goes to each atom. The mixing of atomic orbitals on the same atom to form a new set of equivalent hybrid orbitals. An intermolecular attraction between a hydrogen atom bonded to a highly electronegative atom and a lone pair on a highly electronegative atom in another molecule. A reaction in which a bond is broken by reaction with water or aqueous acid/alkali. A hypothetical gas whose particles have negligible volume and no intermolecular attractions and which obeys the ideal gas equation under all conditions. A solution that obeys Raoult’s law over the complete composition range. The increasing tendency of the outermost s-electron pair to remain non-bonding in heavier p-block elements. A technique that measures absorption of infrared radiation associated with molecular vibrations. The reaction rate measured at, or extrapolated to, the start of a reaction. A step in a free-radical mechanism that generates free radicals. The measurement of NMR signal area used to determine the relative numbers of nuclei contributing to different signals. Bonding with characteristics between ideal ionic and covalent bonding, arising from polarisation of ions. The electrostatic attraction between oppositely charged ions. The equilibrium constant expressed as the product [H₃O⁺][OH⁻] for the self-ionisation of water. Atoms of the same element with the same number of protons but different numbers of neutrons. An organic compound containing a carbonyl group whose carbonyl carbon is bonded to two carbon groups. The enthalpy change when one mole of an ionic solid is completely separated into its gaseous ions. The enthalpy change when one mole of an ionic solid is formed from its gaseous ions under standard conditions. When a system at equilibrium is subjected to a change, the position of equilibrium shifts in the direction that tends to oppose that change. An electron-pair acceptor. An electron-pair donor. An ion or molecule that donates a lone pair of electrons to a central metal ion to form a coordinate bond. Replacement of one or more ligands in a complex by other ligands. A reaction in which one ligand in a complex is replaced by another ligand. The reactant that is completely consumed first and therefore limits the amount of product formed. Weak intermolecular attractions arising from instantaneous dipoles that induce dipoles in neighbouring particles. In addition of an unsymmetrical reagent to an unsymmetrical alkene, the major product is associated with formation of the more stable carbocation intermediate. The electrostatic attraction between positive metal ions and delocalised electrons. The phase in chromatography that moves through or over the stationary phase. The amount in moles of solute per unit volume of solution, commonly expressed in mol dm⁻³. The mass of one mole of a substance. The number of moles of a solute that dissolve per unit volume of saturated solution. The amount of substance containing the Avogadro constant number of specified entities. The actual number of atoms of each element in one molecule of a compound. A formula showing the actual number of atoms of each element in a molecule. An ion formed from a molecule by removal of an electron without fragmentation. The number of reacting particles involved in a single elementary step. A ligand that forms one coordinate bond to a central metal ion. A small molecule capable of joining with many similar or other molecules to form a polymer. A ligand that can form more than one coordinate bond to the same central metal ion. An oxide that shows neither acidic nor basic behaviour under ordinary conditions. An organic compound containing the cyano group, –C≡N. The total number of protons and neutrons in the nucleus of an atom. An electron-pair donor. An addition reaction in which a nucleophile attacks an electron-deficient atom of a multiple bond. A reaction in which a nucleophile replaces an atom or group in a molecule. A species of atom characterised by a particular proton number and nucleon number. Stereoisomerism in which non-superimposable mirror-image molecules rotate plane-polarised light in opposite directions. A region of space around the nucleus that can hold a maximum of two electrons with opposite spins. The power to which the concentration of a reactant is raised in the experimentally determined rate equation; overall order is the sum of these powers. The net movement of solvent through a semipermeable membrane from a region of lower solute concentration to one of higher solute concentration. The minimum pressure that must be applied to a solution to prevent osmosis through a semipermeable membrane. Loss of electrons or an increase in oxidation number. An increase in the oxidation level of carbon, commonly involving gain of oxygen and/or loss of hydrogen. A formal charge assigned to an atom by treating bonding electrons according to electronegativity rules. A species that oxidises another species and is itself reduced. Reaction of a carbon-carbon double bond with ozone to form an ozonide, which can be worked up to give oxidation products such as carbonyl compounds. The pressure that a component gas would exert if it alone occupied the same volume at the same temperature. At a fixed temperature, the ratio of the equilibrium concentrations of a solute distributed between two immiscible solvents, provided the solute has the same molecular form in both. The mass of the pure substance in a sample expressed as a percentage of the total mass of the sample. The actual yield expressed as a percentage of the theoretical yield. The chemical and physical properties of elements vary periodically with atomic number. The recurrence of similar physical and chemical properties at regular intervals when elements are arranged in order of atomic number. A permanent separation of partial positive and partial negative charge in a bond or molecule. The negative base-10 logarithm of the hydronium ion concentration, pH = −log₁₀[H₃O⁺]. A physically distinct, homogeneous part of a system separated from other parts by a boundary. An aromatic compound in which a hydroxyl group is bonded directly to an aromatic ring. A covalent bond formed by sideways overlap of parallel orbitals, with electron density above and below the internuclear axis. The negative base-10 logarithm of the hydroxide ion concentration, pOH = −log₁₀[OH⁻]. Distortion of the electron cloud of an anion or molecule by a nearby positive charge. A macromolecule formed from many repeating monomer-derived units. The relative proportions of reactants and products present in an equilibrium mixture. Structural isomerism in which the same functional group or multiple bond occurs at different positions on the same carbon skeleton. A reaction in solution that forms an insoluble solid. An alcohol in which the carbon bearing the hydroxyl group is bonded to one other carbon atom. A highly pure, stable substance suitable for preparing a solution of accurately known concentration by direct weighing. A step in a free-radical mechanism in which a radical is consumed and another radical is formed. The number of protons in the nucleus of an atom. An equimolar mixture of two enantiomers whose equal and opposite optical rotations give no net rotation of plane-polarised light. An isotope with an unstable nucleus that undergoes radioactive decay. The partial vapour pressure of a component in an ideal solution equals its mole fraction multiplied by the vapour pressure of the pure component at the same temperature. The proportionality constant in a rate equation at a specified temperature. An experimentally determined equation relating reaction rate to reactant concentrations and the rate constant. The change in concentration of a reactant or product per unit time. The slowest elementary step in a reaction mechanism that controls the overall rate. A sequence of elementary steps by which an overall chemical reaction occurs. Purification of a solid by dissolving it in a suitable hot solvent and allowing purer crystals to form on cooling. A species that reduces another species and is itself oxidised. Gain of electrons or a decrease in oxidation number. A decrease in the oxidation level of carbon, commonly involving gain of hydrogen and/or loss of oxygen. The weighted mean mass of an atom of an element relative to one-twelfth of the mass of an atom of carbon-12. The mass of an atom of an isotope relative to one-twelfth of the mass of an atom of carbon-12. The smallest structural unit whose repetition represents the polymer chain. A process in which pressure greater than the osmotic pressure is applied to a solution to force solvent through a semipermeable membrane in the reverse direction to osmosis. The distance travelled by a solute divided by the distance travelled by the solvent front in the same chromatogram. Protection of a metal from corrosion by electrically connecting it to a more easily oxidised metal. Reaction of an ion from a dissolved salt with water, producing an acidic or alkaline solution. The pressure exerted by a vapour in dynamic equilibrium with its liquid or solid at a specified temperature. The energy required to remove one mole of electrons from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions. An alcohol in which the carbon bearing the hydroxyl group is bonded to two other carbon atoms. A covalent bond formed by head-on overlap of orbitals with electron density concentrated along the internuclear axis. Separation or purification by vaporisation followed by condensation, suitable when components have sufficiently different volatilities. A line representation of an organic structure in which carbon atoms and most carbon-bound hydrogen atoms are omitted. A unimolecular nucleophilic substitution mechanism whose rate-determining step involves formation of a carbocation. A bimolecular nucleophilic substitution mechanism occurring in one concerted step involving both substrate and nucleophile. The equilibrium constant for the dissolution of a sparingly soluble ionic solid, expressed using the equilibrium concentrations of its dissolved ions. Separation based on the different solubilities of a substance in two immiscible solvents. Splitting of an NMR signal caused by interaction with neighbouring non-equivalent nuclei. A process that is thermodynamically feasible under the specified conditions without requiring continuous external work. The potential of a half-cell measured relative to the standard hydrogen electrode under standard conditions. The enthalpy change when one mole of gaseous atoms is formed from an element in its standard state under standard conditions. The enthalpy change when one mole of a substance is completely burned in oxygen under standard conditions. The enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions. The enthalpy change associated with removing electrons from gaseous species under standard conditions, as specified by the ionisation process. The enthalpy change when an acid and a base react to form one mole of water under standard conditions. The enthalpy change when a reaction occurs in the stoichiometric amounts shown by its equation under standard conditions, with substances in their standard states. The enthalpy change when one mole of a solute dissolves in sufficient solvent to form an infinitely dilute solution under standard conditions. The enthalpy change when one mole of gaseous ions or molecules becomes solvated by solvent molecules under standard conditions. The entropy of one mole of a substance in its standard state under standard conditions. The reference electrode assigned a standard electrode potential of 0.00 V. A solution whose concentration is accurately known. The phase in chromatography that remains fixed while components of a mixture interact with it. Distillation of a water-immiscible volatile substance with steam so that it distils at a temperature below its normal boiling point. Compounds with the same structural formula but a different arrangement of atoms in space. An acid that is essentially completely ionised in aqueous solution. A base that is essentially completely ionised or dissociated in aqueous solution. A formula showing how atoms are connected within a molecule. Compounds with the same molecular formula but different structural formulae. A reaction in which one atom or group in a molecule is replaced by another. The energies required to remove successive moles of electrons from one mole of gaseous species, one electron per particle at each stage. A substance above its critical temperature and pressure, where distinct liquid and gas phases no longer exist. Dynamic structural isomerism in which two forms interconvert by movement of a proton and a double bond, such as keto-enol tautomerism. A step in a free-radical mechanism in which radicals combine or otherwise react to form products containing no radical. An alcohol in which the carbon bearing the hydroxyl group is bonded to three other carbon atoms. A reference compound assigned a chemical shift of 0 ppm in proton NMR spectroscopy. The resistance of a substance to decomposition when heated. A quantitative technique in which a solution of known concentration is used to determine the amount or concentration of another substance by reaction. An element that forms at least one stable ion with an incomplete d subshell. The unique temperature and pressure at which solid, liquid and vapour phases coexist in equilibrium. The pressure exerted by a vapour above its liquid or solid. The reciprocal of wavelength, commonly expressed in cm⁻¹ in infrared spectroscopy. An acid that is only partially ionised in aqueous solution. A base that reacts only partially with water to establish an equilibrium. Chemistry Definitions
Acid anhydride
Acid dissociation constant Ka
Acid-base indicator
Acidic oxide
Acidity of a base
Activation energy
Acyl chloride
Addition polymerisation
Addition reaction
Alcohol
Aldehyde
Alkane
Alkene
Alkyne
Alpha particle
Amide
Amine
Amphoteric oxide
Amphoteric species
Anode
Arene
Arrhenius acid
Arrhenius base
Atom
Atomic radius
Autocatalysis
Avogadro constant
Azeotrope
Back titration
Base dissociation constant Kb
Base peak
Basic oxide
Basicity (proticity) of an acid
Beta particle
Bidentate ligand
Bond enthalpy
Bond polarity
Born–Haber cycle
Brønsted–Lowry acid
Brønsted–Lowry base
Buffer solution
Carbocation
Carboxylic acid
Catalyst
Catalyst poisoning
Catenation
Cathode
Chain isomerism
Chelate
Chelate effect
Chemical shift
Chiral centre
Chiral molecule
Chromatography
Colligative property
Common ion effect
Complex
Complex ion
Comproportionation
Condensation polymerisation
Condensation reaction
Conformational isomerism
Conjugate acid
Conjugate acid-base pair
Conjugate base
Conjugated system
Coordination number
Corrosion
Covalent bond
Critical temperature
Dalton’s law of partial pressures
Dative covalent bond
Degree of dissociation
Delocalisation
Delocalised electrons
Diazonium ion
Dipole–dipole attraction
Displacement reaction
Displayed formula
Disproportionation
Disproportionation
Dynamic equilibrium
Electrochemical series
Electrode potential
Electrolysis
Electron affinity
Electronegativity
Electrophile
Electrophilic addition
Electrophilic substitution
Electrophilic substitution
Elementary step
Elimination reaction
Empirical formula
Enantiomers
End point
Endothermic process
Enthalpy change
Entropy
Equilibrium constant Kc
Equilibrium constant Kp
Equivalence point
Ester
Esterification
Ether
Excited state
Exothermic process
Faraday constant
Filtration
First ionisation energy
Flame test
Fractional distillation
Fragment ion
Free radical
Free-radical substitution
Fuel cell
Functional group
Functional group isomerism
Galvanic cell
Gamma radiation
Geometrical isomerism
Giant covalent structure
Giant ionic lattice
Gibbs free energy change
Ground state
Half-cell
Half-life
Halogenoalkane
Halogenoarene
Hess’s law
Heterogeneous catalyst
Heterogeneous equilibrium
Heterolytic fission
Homogeneous catalyst
Homogeneous equilibrium
Homologous series
Homolytic fission
Hybridisation
Hydrogen bond
Hydrolysis
Ideal gas
Ideal solution
Inert pair effect
Infrared spectroscopy
Initial rate
Initiation step
Integration
Intermediate bonding
Ionic bond
Ionic product of water Kw
Isotope
Ketone
Lattice enthalpy of dissociation
Lattice enthalpy of formation
Le Chatelier’s principle
Lewis acid
Lewis base
Ligand
Ligand exchange
Ligand substitution
Limiting reagent
London dispersion forces
Markovnikov’s rule
Metallic bond
Mobile phase
Molar concentration
Molar mass
Molar solubility
Mole
Molecular formula
Molecular formula
Molecular ion
Molecularity
Monodentate ligand
Monomer
Multidentate ligand
Neutral oxide
Nitrile
Nucleon number
Nucleophile
Nucleophilic addition
Nucleophilic substitution
Nuclide
Optical isomerism
Orbital
Order of reaction
Osmosis
Osmotic pressure
Oxidation
Oxidation in organic chemistry
Oxidation number
Oxidising agent
Ozonolysis
Partial pressure
Partition coefficient
Percentage purity
Percentage yield
Periodic law
Periodicity
Permanent dipole
pH
Phase
Phenol
Pi bond
pOH
Polarisation
Polymer
Position of equilibrium
Positional isomerism
Precipitation reaction
Primary alcohol
Primary standard
Propagation step
Proton number
Racemic mixture
Radioisotope
Raoult’s law
Rate constant
Rate equation
Rate of reaction
Rate-determining step
Reaction mechanism
Recrystallisation
Reducing agent
Reduction
Reduction in organic chemistry
Relative atomic mass
Relative isotopic mass
Repeating unit
Reverse osmosis
Rf value
Sacrificial protection
Salt hydrolysis
Saturated vapour pressure
Second ionisation energy
Secondary alcohol
Sigma bond
Simple distillation
Skeletal formula
SN1 mechanism
SN2 mechanism
Solubility product Ksp
Solvent extraction
Spin-spin splitting
Spontaneous process
Standard electrode potential
Standard enthalpy change of atomisation
Standard enthalpy change of combustion
Standard enthalpy change of formation
Standard enthalpy change of ionisation
Standard enthalpy change of neutralisation
Standard enthalpy change of reaction
Standard enthalpy change of solution
Standard enthalpy change of solvation
Standard entropy
Standard hydrogen electrode
Standard solution
Stationary phase
Steam distillation
Stereoisomers
Strong acid
Strong base
Structural formula
Structural isomers
Substitution reaction
Successive ionisation energies
Supercritical fluid
Tautomerism
Termination step
Tertiary alcohol
Tetramethylsilane (TMS)
Thermal stability
Titration
Transition element
Triple point
Vapour pressure
Wavenumber
Weak acid
Weak base