Combined Science key terms

A mineral ion absorbed by plant roots from the soil that supplies nitrogen for making amino acids.

The conversion of ammonium compounds into nitrites and then nitrates by nitrifying bacteria in soil.

The conversion of atmospheric nitrogen gas into nitrogen compounds by nitrogen-fixing bacteria.

An element in Group 0 of the periodic table whose atoms have a full outer electron shell and a stable electron arrangement.

A disease that cannot be passed from one person to another.

A force that acts between objects without them needing to touch, such as magnetic attraction or repulsion.

A system in which matter can enter or leave, such as a reaction taking place in an open container.

Unable to burn.

A species that does not occur naturally in a particular area and has been introduced there.

A component whose current–potential difference graph is not a single straight line, so current and potential difference are not directly proportional.

A relationship represented by a curved rather than a straight line on a graph.

An element that does not form positive ions in its characteristic chemical reactions.

An energy resource with a finite supply that is not replenished as it is used.

A natural resource that cannot be replaced on a human timescale, such as metal ores or fossil fuels.

A protective mechanism that acts against many different pathogens rather than targeting one particular pathogen.

Motion in which an object's speed changes.

An imaginary line perpendicular to a boundary at the point where a ray meets it.

A supporting contact force exerted by a surface, acting perpendicular to that surface.

An equation representing a change in a nucleus, showing the original nucleus and the nucleus and radiation produced.

An atomic model with a tiny, positively charged central nucleus containing most of the atom’s mass, surrounded by electrons and mostly empty space.

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: $^{A}_{Z}\mathrm{X}$.

A proton or neutron in an atomic nucleus.

A subunit of DNA consisting of a sugar, a phosphate group and one of four bases attached to the sugar.

The small, dense central region of an atom containing protons and neutrons and almost all of the atom’s mass.

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).