Edexcel GCSE Combined Science key terms

The combination of alleles an organism has.

A continuous network of very many atoms joined by strong covalent bonds, rather than separate small molecules.

A large, regular, repeating arrangement of positive and negative ions held together by strong electrostatic attractions.

An increase in the Earth's average surface temperature.

A hormone released by the pancreas that raises blood glucose concentration by stimulating the liver to break down glycogen and release glucose.

An insoluble carbohydrate used to store glucose in liver and muscle cells.

The change in the vertical-axis quantity divided by the corresponding change in the horizontal-axis quantity. On a velocity–time graph, gradient gives acceleration.

A single layer of carbon atoms, one atom thick, with each atom covalently bonded to three others in a hexagonal network.

The force per kilogram acting on a mass in a gravitational field, measured in newtons per kilogram (N/kg).

Energy stored because of an object's position in a gravitational field, measured relative to a chosen height.

The natural warming of the Earth caused by atmospheric gases absorbing outgoing infrared radiation and re-emitting some energy towards the surface.

An atmospheric gas that absorbs infrared radiation emitted by the Earth and subsequently releases energy. Examples include carbon dioxide, methane and water vapour.

A vertical column in the periodic table. Elements in the same group have similar chemical properties because their atoms have similar outer-shell electron arrangements.

A permanent increase in the size or mass of an organism.

A specialised cell that works with another guard cell to control whether a stoma is open or closed.

The industrial manufacture of ammonia by reacting nitrogen with hydrogen using an iron catalyst at 450 °C and 200 atmospheres.

The place where an organism lives.

The protein in red blood cells that binds oxygen and transports it around the body.

An equation showing the reaction at one electrode, including the electrons transferred; both atoms and total charge must balance. Writing half equations is higher-tier content.

The time taken for half the undecayed nuclei of a radioactive isotope to decay, or for the activity of a source to fall to half its value.

A negative ion formed when a halogen atom gains one electron; it has a charge of −1.

An element in Group 7 of the periodic table, whose atoms have seven electrons in their outer shell.

Having one set of chromosomes: half the number present in a diploid cell.

A nucleus containing one set of chromosomes: half the normal number found in body cells.

A substance, object or situation that could cause harm, such as a corrosive chemical or hot apparatus.

A pictogram used to warn people about the dangers associated with a substance.

A state of complete physical, mental and social well-being, not merely the absence of disease or infirmity.