OCR GCSE Chemistry A key terms

A numerical scale used to compare the relative acidity or alkalinity of an aqueous solution.

A graph showing how pH changes as measured volumes of an acid or alkali are added during a titration.

A layer that prevents substances such as oxygen and water from reaching a metal surface.

A change in which no new substance is formed; the particles keep their chemical identity although their arrangement, movement, spacing or state may change.

A physical characteristic that can be observed or measured without forming a new substance, such as colour, state or melting point.

Extraction of metal compounds using plants that absorb them through their roots.

A horizontal part of a graph showing that the measured quantity is no longer changing.

A polymer whose chain contains amide links; nylon is a polyamide.

An ion containing more than one covalently bonded atom, such as hydroxide, $OH^-$, or sulfate, $SO_4^{2-}$.

A polymer whose chain contains ester links, $-\mathrm{C(=O)-O}-$.

A large molecule made by joining many smaller units together in a chain.

The relative amounts of reactants and products present when a reversible reaction reaches equilibrium.

A positive correlation is a pattern in which two measured quantities tend to increase together.

A positively charged ion formed when an atom loses one or more electrons.

An atom or group of atoms with an overall positive charge, formed when electrons are lost.

A positively charged particle formed when a metal atom loses one or more electrons.

Water that is safe to drink, although it may contain small amounts of dissolved substances.

A difference in electrical energy per unit charge between two points, measured in volts.

An insoluble solid formed when ions in solutions react together.

Repeated results that are close to one another.

The force exerted by a gas on each unit area of a surface.

An alcohol in which the carbon attached to the –OH group is bonded to no more than one other carbon atom. It can be oxidised to a carboxylic acid.

A new substance formed by a chemical reaction.

A naturally occurring polymer made from amino acid monomers.

A positively charged sub-atomic particle found in an atomic nucleus.

A convenient measurement that represents another quantity; for a fixed reaction endpoint, $1/t$ can represent relative rate.

A substance containing only one element or one compound, rather than a mixture of substances.