OCR GCSE Chemistry A key terms

The solid left on filter paper after filtration.

The smallest change in a quantity that a measuring instrument can distinguish.

The time between injecting a sample into a gas chromatograph and a component producing its maximum detector response.

Using a product again without processing it into a new material.

A method of separating water from dissolved salts by forcing it through a membrane that lets water pass but holds back the salts.

The direction of a reversible reaction in which the products form the original reactants.

A reaction in which products can react to form the original reactants.

The distance moved by a spot divided by the distance moved by the solvent front, both measured from the start line.

The possibility of harm, taking account of both what a material might do and whether people or the environment are exposed to it.

The conditions of room temperature and ordinary atmospheric pressure, abbreviated to RTP.

Replacing a number with a nearby value written to a specified level of precision.

The corrosion of iron or steel when both oxygen and water are present, producing hydrated iron(III) oxide.

Protection in which an electrically connected, more reactive metal corrodes instead of the metal being protected.

An ionic compound made of positive and negative ions; a metal salt solution contains dissolved metal ions.

The typical range of sizes associated with an object or particle.

A number showing how many times as large one value is as another; it is calculated as new value divided by original value for the same quantity.

A scientific representation used to describe and explain features that may be difficult to observe directly.

The separation of suspended solids from a liquid by allowing the solids to settle.

The ability of a method to detect small amounts of a substance or small changes in its amount.

A device that detects a substance or a change in its surroundings and produces a response that can be measured.

A pair of electrons shared between two atoms in a covalent bond.

A pair of outer-shell electrons shared between two atoms; one shared pair forms one covalent bond.

The reduction in the attraction between the nucleus and an outer or incoming electron caused by electrons in inner shells.

A digit that contributes to the stated precision of a measured or calculated value, counted from the first non-zero digit.

The digits in a number that convey its precision, counted from the first non-zero digit.

Shapes that have the same proportions but may be different sizes.

A technique that boils and then condenses a liquid, commonly to recover a solvent from a solution.