Key terms & definitions

A polymer that softens when heated and hardens when cooled, allowing it to be reheated and reshaped. Also called a thermoplastic.

An image made using infrared radiation that shows differences in the surface temperatures of objects.

Ocean circulation driven by differences in water density caused by temperature and salinity.

A nuclear weapon, also called a hydrogen bomb or H-bomb, capable of much greater explosive power than early atomic bombs.

A polymer that softens when heated and hardens when cooled, allowing it to be shaped using heat.

A narrow pass between mountains and the sea in central Greece, where a Greek allied force resisted Xerxes’ invasion in 480 BCE. Its name means ‘Hot Gates’.

A temperature-sensitive receptor that detects a change in temperature.

The control of body temperature to keep internal conditions suitable for cells.

A coordination centre in the brain that monitors body temperature and brings about responses when it changes.

A plastic that sets permanently during curing and cannot subsequently be softened and reshaped by heating.

A polymer with strong cross-links between its chains, so it does not melt when heated.

A polymer with covalent cross-links forming a network that does not soften or melt on heating.

A polymer that sets permanently during curing and cannot subsequently be melted and reshaped.

A polymer whose separate chains can move past one another when heated, allowing the material to melt and be reshaped.

A polymer that softens on heating and can be reshaped because its chains can move past one another.

A device that controls heating or cooling to maintain a chosen temperature.

A concise statement of the overall interpretation that an essay develops and supports.

The central claim of an essay: a concise answer to the question which the rest of the response develops and supports.

A festival honouring Demeter and Persephone, concerned with agricultural and human fertility; in Athens, participation was restricted to citizens' wives.

The poorest class of Athenian citizens, who served mainly as rowers and light troops.

The distance between the two opposite faces of a sheet.

A person paid to recover stolen property and sometimes deliver suspected thieves to the authorities.

A Viking assembly where free men discussed laws, settled disputes and made decisions.

The distance a vehicle travels during the driver's reaction time, before the brakes are applied.

The distance a vehicle travels during the driver's reaction time, before the brakes are applied.

The time a driver takes to recognise a hazard, react and apply the brakes.

Chromatography carried out using a thin layer of silica gel or alumina coated onto a glass, metal or rigid plastic support.

Chromatography using a thin layer of silica or alumina on a supporting plate as the stationary phase, with a liquid solvent as the mobile phase.

A simplified model in which all refraction is represented as occurring at one line through the lens.

Removing selected trees to give the remaining trees more space to develop.