Edexcel GCSE Combined Science key terms

The separation of light into its constituent colours because different wavelengths travel at different speeds in a material and are refracted by different amounts.

The straight-line distance and direction from an object's starting position to its finishing position. Displacement is a vector measured in metres (m).

A reaction in which a more reactive element replaces a less reactive element in a compound.

The spreading out of energy into less useful stores, usually thermal stores of the surroundings.

The separation of a substance into ions when it dissolves; an acid dissociates to produce hydrogen ions.

The process in which a substance mixes into a liquid to form a solution.

The total length of the route travelled by an object. Distance is a scalar measured in metres (m).

A graph showing how distance changes with time. Its gradient gives speed.

The liquid collected after vapour condenses during distillation.

A separation process in which a liquid is evaporated and its vapour is cooled and condensed, allowing the liquid to be collected.

A change in an object's shape caused by forces, such as stretching, bending or compression.

The pattern of where organisms occur within an area.

Deoxyribonucleic acid: the genetic material, consisting of two nucleotide strands coiled into a double helix.

Determining the order of the bases in a DNA molecule.

The highest level of biological classification in the three-domain system, above kingdom.

An allele expressed in the phenotype when one copy is present, including in a heterozygous individual.

The amount of a medicine given at one time.

A device worn by someone working with radiation to monitor their accumulated radiation dose.

A representation of electrons using dots and crosses to distinguish electrons originally belonging to different atoms.

A representation of outer-shell electrons that uses dots and crosses to distinguish electrons supplied by different atoms.

A trial in which neither the participants nor the doctors assessing them know who receives the active drug and who receives the placebo during the trial.

A covalent bond in which two atoms share two pairs of electrons.

A circulatory arrangement in which blood passes through the heart twice during one complete journey through the lungs and the rest of the body.

The shape formed by two strands coiled around one another, like a twisted ladder.

The spread of pathogens in droplets released when an infected person coughs, sneezes or talks.

A prolonged period of unusually low rainfall.

A state in a closed system in which the forward and reverse reactions continue at equal rates, so the concentrations of reactants and products remain constant.

A safety wire connecting an appliance’s metal case to earth, providing a low-resistance path for current if the case becomes live.