Edexcel GCSE Combined Science key terms

The breakdown of larger alkane molecules into smaller, more useful molecules, including alkanes and alkenes.

The internal volume of a skull’s braincase, used to estimate brain size.

Growing different crops on the same land in successive growing seasons; including legumes can help replenish soil nitrogen.

A complex, finite mixture of hydrocarbons whose carbon atoms are arranged in chains or rings.

The formation of solid crystals from a solution, for example as water evaporates or a concentrated solution cools.

The rate of flow of electric charge, measured in amperes (A).

Division of the cytoplasm to form two separate daughter cells.

The material inside a cell where many chemical reactions take place.

The nucleus remaining after a radioactive decay.

A decrease in speed; acceleration acting opposite to the direction of motion.

An organism, such as a bacterium or fungus, that breaks down dead organisms and waste, returning nutrients to the environment.

The breakdown and digestion of dead organisms and biological waste by decomposers.

Water from which dissolved ions have been removed, used to avoid interference in chemical analysis.

An electron that is not confined to one atom or one covalent bond and can move through part of a structure.

A change in an enzyme’s shape, including its active site, that prevents its substrate from fitting effectively.

A short, branched extension of a neurone that receives signals.

An extension of a sensory neurone that carries electrical impulses towards its cell body.

The conversion of nitrates into nitrogen gas by denitrifying bacteria, particularly in oxygen-poor soil.

The mass per unit volume of a substance: $\rho = m/V$. Its SI unit is kg/m³.

The change directly from gas to solid, without becoming a liquid.

The removal of dissolved salts from sea water.

The process by which a cell becomes specialised to carry out a particular function.

The net movement of particles from a region of higher concentration to a region of lower concentration.

A solution containing a relatively small amount of dissolved substance per unit volume of solution.

A component that allows appreciable current in one direction but has very high resistance in the opposite direction.

Having two sets of chromosomes, one inherited from each parent.

An electric current in which charge moves in one direction only.