OCR GCSE Combined Science A key terms

A comparison made by dividing one quantity by another, or expressing their relative sizes using a colon.

Original measurements or observations before any calculations are carried out.

A starting material used to make a material or product, such as a metal ore or crude oil.

A starting substance that is changed during a chemical reaction.

The physical circumstances in which a reaction takes place, such as temperature.

A force exerted on an object by a surface or support in contact with it.

A diagram showing how energy changes as a chemical reaction progresses, including the relative energies of reactants and products.

The time between detecting a stimulus, such as a road hazard, and responding to it.

How readily a substance undergoes a chemical reaction. A more reactive metal loses electrons and forms positive ions more readily.

A list placing metals in order of their reactivity. Hydrogen is included as a reference for predicting which metals react with dilute acids to release hydrogen gas.

An answer to an investigation’s question that is supported by evidence and scientific reasoning.

An account that connects evidence to a conclusion using scientific knowledge and logical reasoning.

A cell or group of cells that detects a stimulus.

A molecule that detects a particular signal, allowing a cell to respond to its surroundings or communicate with other cells.

An allele expressed in the phenotype only when two copies are present, in a simple dominant–recessive inheritance model.

DNA formed by joining genetic material from different sources.

Collecting and processing used materials so that they can be made into new products.

A specialised blood cell that transports oxygen from the lungs to body tissues.

A reaction in which electrons are transferred, so oxidation and reduction occur together.

A substance that causes another substance to lose oxygen. In an oxygen-transfer reaction, the reducing agent gains oxygen and is oxidised.

The gain of electrons by a substance.

A known substance used for comparison to help identify an unknown substance.

The return of a wave into its original medium after meeting a surface or boundary.

A rapid, automatic and involuntary response to a stimulus.

The nerve pathway that carries information from a receptor to an effector during a reflex action.

Replanting trees in an area where forest has been removed.

A change in a wave’s direction as it crosses a boundary at an angle because its speed changes.