79 of the Chemistry glossary’s terms, each with the part of the syllabus where you first meet it.
A graph of a measured property (such as absorbance) against the known concentrations of standard solutions, used to read off the concentration of an unknown sample.
An insulated container in which a reaction heats or cools a known mass of water or solution so that the heat transferred can be measured.
The measurement of the heat transferred in a chemical or physical change, usually from the temperature change of a known mass of water or solution.
An ion with a negative charge on a carbon atom, which carries a lone pair, such as .
An ion with a positive charge on a carbon atom that has only three bonds, such as
Removing carbon dioxide from the waste gases of power stations or factories, compressing it and storing it permanently, usually in porous rock deep underground.
The total mass of greenhouse gases released by producing and using a product or carrying out an activity, expressed as the equivalent mass of carbon dioxide.
Describes a fuel or activity that adds no net carbon dioxide to the atmosphere, for example because the carbon dioxide released was recently absorbed by photosynthesis. Biofuels are only approximately carbon neutral.
A C=O double bond whose carbon is bonded only to carbon or hydrogen atoms; found as –CHO in aldehydes and C–CO–C in ketones.
The functional group –COOH, a C=O and an OH on the same carbon atom; it defines the carboxylic acids.
A compound containing the carboxyl group, –COOH, general formula
A substance that increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy, and is chemically unchanged at the end of the reaction.
Loss of activity of a heterogeneous catalyst when a substance binds strongly to its surface and blocks the sites where reactants would bind, as lead does in catalytic converters.
A device in a vehicle exhaust in which platinum, palladium and rhodium on a ceramic honeycomb catalyse the conversion of carbon monoxide, unburnt hydrocarbons and nitrogen oxides into carbon dioxide, water and nitrogen.
The ability of atoms of an element to bond to each other to form chains and rings. Carbon shows it strongly because C–C bonds are strong.
The electrode at which reduction takes place. In a voltaic cell (including a fuel cell) it is the positive electrode.
A positively charged ion, with fewer electrons than protons; metals form cations by losing electrons.
Structural isomers with the same functional group but different carbon skeletons, such as butane and 2-methylpropane.
A reaction in which a reactive intermediate, such as a radical, is regenerated in each cycle of steps, so one initiation event leads to many product molecules.
The charge of an ion relative to its size; small, highly charged ions have a high charge density and attract electrons or other ions strongly.
The position of an atom in a molecule, defined by the atoms and groups around it; in NMR each different hydrogen environment gives one signal.
A representation of a reaction using formulas, with reactants on the left and products on the right of an arrow; when balanced, it has the same number of each kind of atom on both sides.
The study of the rates of chemical reactions, the factors that affect them and the mechanisms by which reactions take place.
The position of an NMR signal relative to the signal of TMS, symbol , in parts per million (ppm); it depends on the chemical environment of the hydrogen atoms.
Describes a molecule (or object) that cannot be superimposed on its mirror image, such as a molecule with one chiral carbon atom.
A carbon atom bonded to four different atoms or groups, marked with an asterisk (). A molecule with one chiral carbon exists as a pair of enantiomers.
The industrial electrolysis of brine, producing chlorine at the anode and hydrogen and sodium hydroxide at the cathode.
A compound of carbon, chlorine and fluorine, such as
A technique that separates the components of a mixture by their different distribution between a stationary phase and a mobile phase that moves through or over it.
The stereoisomer in which the two identical or similar groups lie on the same side of a C=C double bond or on the same face of a ring.
Stereoisomerism caused by restricted rotation about a C=C bond or a ring, possible only when each of the two carbon atoms involved carries two different atoms or groups.
A reaction set up to give a sudden visible change once a fixed amount of reaction has taken place, so the time taken measures the rate (rate is proportional to ).
An arrangement of equal spheres, such as the atoms of many metals, that leaves the least empty space; each atom has twelve nearest neighbours.
A system that can exchange energy but not matter with its surroundings, so no reactant or product enters or leaves.
The number in front of a formula in a balanced equation; the coefficients give the ratio of the amounts, in moles, of the substances that react and form.
The statistic , between 0 and 1, that measures how closely data points fit a trend line; a value of 1 means every point lies exactly on the line.
The number of collisions between particles per unit time in a given volume; it increases with concentration, pressure, surface area and temperature.
The relative orientation of particles when they collide; only some orientations bring the atoms that must bond into contact, so only those collisions can lead to reaction.
The theory that particles react only when they collide with a combined kinetic energy at least equal to the activation energy and with the proper orientation.
Presenting work as individual when it was produced with, or copied from, another student; a form of academic misconduct, unlike permitted collaboration.
Measuring the absorbance of a coloured solution at a chosen wavelength to find its concentration, using a calibration curve of standard solutions.
A circle of the visible colours (red, orange, yellow, green, blue, violet) with their wavelength ranges, printed in the data booklet, in which complementary colours lie opposite each other.
For a fixed amount of gas,
An exothermic reaction of a substance with oxygen. Complete combustion of a compound of carbon, hydrogen and oxygen in excess oxygen gives only carbon dioxide and water.
Finding the empirical formula of an organic compound by burning a weighed sample in excess oxygen and weighing the carbon dioxide and water formed; oxygen is found by difference.
The instruction word at the start of a question part, such as state, explain or deduce, which sets the type and depth of answer expected.
The colour opposite a given colour on the colour wheel. A substance that absorbs light of one colour appears the complementary colour.
A central metal ion surrounded by ligands bonded to it by coordination bonds, such as
A material made of two or more distinct materials that stay separate within it, combining their properties, such as reinforced concrete or fibreglass.
A substance made of atoms of two or more different elements chemically bonded together in a fixed ratio; its properties differ from those of its elements.
Industrial conditions chosen to balance an acceptable equilibrium yield against an acceptable rate and cost, when the conditions that favour each conflict.
A reaction in which bond breaking and bond making happen at the same time in a single step, with no intermediate, as in the mechanism.
Titres that agree closely, usually within ; the mean of the concordant titres is used in the calculation.
The change of state from gas to liquid, which releases energy (exothermic).
A polymer formed by condensation reactions between monomers that each have two functional groups, with a small molecule (usually water or hydrogen chloride) released as each link forms.
A reaction in which two molecules join to form a larger molecule with the release of a small molecule such as water or hydrogen chloride.
An electron configuration in which the inner electrons are written as the preceding noble gas in square brackets, for example for potassium.
A formula that shows the atoms bonded to each carbon atom in order along the chain without drawing every bond, e.g.
The species formed when a base has gained one proton: the conjugate acid of is
Two species that differ by a single proton, , such as
The species left when an acid has lost one proton: the conjugate base of is
The industrial manufacture of sulfuric acid, in which sulfur dioxide is oxidized to sulfur trioxide,
A bond drawn through the bracket at each end of a repeating unit, showing where the unit joins the next one in the polymer chain.
A spectrum containing all wavelengths over a range with no gaps, such as white light from a filament lamp passed through a prism.
A variable that can take any value within its range, such as temperature, concentration or volume.
A variable that could affect the dependent variable and is therefore kept constant, so that only the independent variable is changed.
The narrowing of the spacing between successive lines of a spectral series at higher frequency, until they merge, because the energy levels get closer together at higher energy.
The frequency at which the lines of a spectral series merge; for the series ending on the ground state it corresponds to ionization of the atom.
A graph of temperature against time for a substance as it cools; a pure substance gives a flat plateau at its freezing point, an impure one a gradual slope.
A covalent bond in which both electrons of the shared pair come from the same atom, as in the fourth N–H bond of .
In a lattice, the number of nearest neighbours of opposite charge around an ion (six in sodium chloride); in a complex ion, the number of coordination bonds to the central ion.
The gradual oxidation of a metal at its surface by substances in its surroundings, such as oxygen and water.
The electrostatic attraction between a shared pair of electrons and the positively charged nuclei of the two bonded atoms.
A lattice of atoms joined by covalent bonds throughout, with no separate molecules, as in diamond, silicon and silicon dioxide.
A covalent bond joining two neighbouring polymer chains; cross-links make a polymer more rigid and stop it softening on heating.
A liquid fossil fuel made of a mixture of hundreds of hydrocarbons, separated by fractional distillation into fractions such as petrol, kerosene and diesel.
The formation of crystals of a solute from a saturated solution, usually by evaporating some solvent and then cooling slowly.
A curved arrow with a full arrowhead, used in mechanisms to show the movement of a pair of electrons, from a lone pair or bond to the atom or bond where the pair ends up.
A saturated hydrocarbon whose carbon atoms form a ring, general formula