Chemistry key terms

Agreement between repeated measurements made using the same method.

A selected part of a repeating structure which can be continued to represent more of the structure.

A group of atoms whose pattern occurs many times along a polymer molecule.

A measurement made again under the same conditions so that the spread of the results can be assessed.

The smallest group of atoms that repeats along a polymer chain.

A model that represents a system using objects, images, symbols or an analogy, such as a ball-and-stick molecule.

A sample chosen so that testing it gives a fair indication of the material it is intended to represent.

The closeness of results obtained when measurements are repeated by different people or using different equipment or methods.

The process in which another scientist carries out an investigation independently to see whether comparable findings can be obtained.

The risk that remains after control measures have been put in place.

The insoluble solid left on filter paper during filtration.

How strongly a metal opposes being oxidised; a metal with greater resistance is less easily oxidised.

The smallest change that a measuring instrument can distinguish.

Health difficulties affecting breathing or the organs and airways used for breathing.

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

Using a product again without turning its material into a new product.

A desalination process in which pressure forces water through a partially permeable membrane while dissolved salts are retained.

The right-to-left reaction in a reversible equation, in which the products of the forward reaction reform its reactants.

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

A unitless ratio equal to the distance moved by a substance divided by the distance moved by the solvent.

The possibility that something will cause harm, considered alongside how serious that harm could be.

A systematic process of identifying hazards, judging their risks and selecting measures that reduce those risks.

A structured comparison of the advantages and possible harms of an action, including who receives the benefits and who bears the risks.

A judgement that compares the advantages of an application with its possible harms.

A factor that changes the probability of an outcome without producing that outcome in every case.

A step taken to make harm less likely or to limit its effects while, where possible, retaining the benefits of an activity.

The usual temperature of the surroundings; in this context it is about 20 °C.

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

The usual conditions under which the GCSE molar gas volume is used, commonly taken as $20\,^{\circ}\text{C}$ and a pressure of one atmosphere.

Changing a number to a stated level of precision by using the next digit to decide whether the final retained digit stays the same or increases by one.