Edexcel GCSE Combined Science key terms

A diagram showing how energy changes as a reaction progresses, including the reactant and product energy levels and the activation-energy barrier.

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

An arrangement of metals in order of reactivity. Carbon is included as a comparison point when choosing extraction methods.

An allele expressed in the phenotype only when two copies are present in the simple inheritance patterns studied here.

DNA formed by joining genetic material from different sources.

Processing waste material so that it can be used to make new products.

A specialised blood cell that transports oxygen using haemoglobin; also called an erythrocyte.

A reaction in which oxidation and reduction occur together, involving transfer of electrons.

The gain of electrons by a substance in a reaction.

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

The nerve pathway responsible for a rapid, automatic response to a stimulus.

Replanting trees in an area where forest has been removed.

A change in the direction of a wave as it passes between substances because its speed changes. There is no change in direction when it crosses along the normal.

The weighted mean mass of an atom of an element relative to one-twelfth of the mass of a carbon-12 atom. It has no unit.

Dating that establishes whether an object is older or younger than another, rather than giving its age in years.

The sum of the relative atomic masses of all the atoms represented in a chemical formula. Its symbol is $M_r$, and it has no unit.

The sum of the relative atomic masses of all the atoms in one molecule, written as $M_r$. It has no unit.

A mass compared with a standard based on carbon-12, with no unit. Use relative atomic mass for atoms and relative molecular or formula mass for molecules or formula units.

A neurone within the central nervous system that connects other neurones, including sensory and motor neurones.

An energy resource that is replenished naturally at least as quickly as it is used, provided it is managed sustainably.

The solid left on the filter paper during filtration.

A measure of how strongly a component opposes the flow of current, measured in ohms (Ω).

The smallest change in a quantity that a measuring instrument can distinguish.

Chemical reactions in cells that release energy from nutrients. Aerobic respiration uses oxygen and releases carbon dioxide and water.

Apparatus used to measure the rate of respiration, commonly by measuring oxygen uptake.

An enzyme that cuts DNA at particular recognition sequences.

The single force that has the same overall effect as all the forces acting on an object combined.