OCR GCSE Chemistry A key terms

The SI unit for amount of substance; amounts in moles can be compared using the coefficients in a balanced chemical equation.

A formula that gives the number of atoms of each element in one molecule without showing how they are connected.

An ion formed from a whole molecule without its breaking into smaller fragments.

The spatial arrangement of atoms in a molecule.

A group of atoms joined by covalent bonds.

The amount of substance containing a specified number of particles; it is not a unit of mass.

The whole-number relationship between amounts in moles, given by the coefficients in a balanced equation.

Changed into the liquid state by heating.

A small molecule that can join with others to form a polymer.

A calculation in which the result of one operation is used in a later operation.

A unit of length equal to $10^{-9}$ metres, with symbol nm.

A unit of length equal to one billionth of a metre: $1\,\text{nm}=10^{-9}\,\text{m}$.

A particle with dimensions on the nanometre scale whose properties may differ from those of the same material in bulk.

A material made of particles with dimensions on the scale of about 1–100 nanometres.

The range of dimensions measured in nanometres, usually referring to dimensions from about 1 nm to 100 nm.

An organic compound described as natural because its source in that context is an organism or another natural process; the same compound may also be synthesised.

A negatively charged ion formed when an atom gains one or more electrons.

Neither acidic nor alkaline; a neutral aqueous solution has a pH of 7.

A reaction in which an acid reacts with a base, including an alkali, to form a salt and water.

The condition in which the concentrations of hydrogen ions and hydroxide ions are equal; a neutral solution has pH 7.

An uncharged sub-atomic particle found in an atomic nucleus.

An element in Group 0 of the periodic table whose atoms have a full outer electron shell and are therefore very unreactive.

A solvent other than water, such as ethanol or propanone.

A reaction system that can exchange substances, including gases, with its surroundings.

A metal that is not iron, such as copper.

An electrode whose material takes part in the reaction; a copper anode dissolves during electrolysis of copper sulfate solution.

An element whose atoms commonly gain or share electrons in reactions.