AQA GCSE Combined Science Trilogy key terms

A way of representing an atom using its element symbol, with its mass number at the upper left and atomic number at the lower left: $^{A}_{Z}\mathrm{X}$.

The small central region of an atom containing its protons and neutrons, where almost all of the atom’s mass is concentrated.

An excess of body fat that increases the risk of conditions including Type 2 diabetes.

A reproductive hormone produced by the ovaries that causes female secondary sex characteristics to develop and rebuilds the uterus lining. It also helps regulate other menstrual-cycle hormones.

A conductor whose current is directly proportional to the potential difference across it, provided its temperature remains constant.

A meter that measures electrical resistance directly, in ohms (Ω).

The conditions under which a process functions best.

The dose that provides effective treatment while keeping harmful side effects as low as possible.

The pH at which an enzyme-catalysed reaction proceeds fastest under the conditions being investigated.

The temperature at which a process has its highest rate under the given conditions.

A factor of ten in the size of a quantity. A factor of $10^3$, or 1000, represents a difference of three orders of magnitude.

A naturally occurring rock containing enough of a metal or metal compound to make extracting the metal worthwhile.

A structure made of different tissues working together to carry out particular functions.

Material originating from living organisms, such as faeces and food waste, which microorganisms can break down.

A single living individual.

A group of organs working together to carry out a particular function.

The pencil line on chromatography paper where the samples are placed before separation begins; also called the baseline.

A repeated change or back-and-forth movement about a central position.

An instrument that displays how an electrical signal changes with time; microphone signals can be used to measure sound arrival times.

The net movement of water through a partially permeable membrane from a dilute solution to a more concentrated solution.

Obtaining a shared, limited resource more successfully than another species, reducing the resources available to that species.

An electron in the outermost occupied shell of an atom. Outer electrons determine how an atom takes part in chemical reactions.

The highest occupied electron shell of an atom; its electrons strongly influence the atom's chemical reactions.

The difference between the total energy needed to break reactant bonds and the total energy released when product bonds form.

The release of an egg from an ovary.

The loss of electrons by a particle.

Gases made of nitrogen and oxygen, collectively written as $\mathrm{NO_x}$, that cause respiratory problems and contribute to acid rain.