Combined Science key terms

The reduction in the attraction between the nucleus and an outer electron caused by electrons in inner shells.

A perforated end wall between adjoining phloem sieve-tube cells, allowing dissolved substances to pass through.

A digit counted when expressing the precision of a number. Counting starts at the first non-zero digit and includes zeros between significant digits and trailing decimal zeros.

Silicon dioxide, $\mathrm{SiO_2}$: a substance made from silicon and oxygen atoms in a giant covalent structure.

Separation in which a liquid is vaporised and its vapour is then cooled and condensed for collection, for example obtaining water from salt solution.

A substance consisting of separate, small molecules, with covalent bonds within each molecule and intermolecular forces between molecules.

A small group of atoms held together by covalent bonds, such as hydrogen, $\mathrm{H_2}$, or water, $\mathrm{H_2O}$.

A unit belonging to the International System of Units, the standard system used for scientific measurements.

A measure of how acidic or alkaline soil is.

A wire wound into a coil with many turns, which produces a magnetic field when it carries a current.

Able to dissolve in a solvent. A soluble salt dissolves in water to form a salt solution.

A substance dissolved in a solvent to form a solution, such as sugar dissolved in water.

A mixture formed when a solute dissolves in a solvent.

A liquid in which a solute dissolves.

The furthest point reached by the solvent during chromatography.

Tiny solid carbon particles produced during incomplete combustion of carbon-containing fuels.

A cell with a structure suited to carrying out a particular function.

The evolution of a new species.

The smallest group in the Linnaean hierarchy, whose organisms share the most characteristics.

The geographical pattern of where a species lives.

The amount of energy required to raise the temperature of one kilogram of a substance by one degree Celsius, measured in J/(kg °C).

The energy required to change the state of one kilogram of a substance with no change in temperature, measured in J/kg.

The energy required to change one kilogram of a substance from solid to liquid with no change in temperature. The same amount is released when one kilogram freezes.

The energy required to change one kilogram of a substance from liquid to vapour with no change in temperature. The same amount is released when one kilogram condenses.

A biological sample prepared for examination, such as a thin layer of onion tissue on a microscope slide.

An ion that remains unchanged during a reaction and is omitted from the final ionic equation.

How fast an object is moving, without specifying its direction; a scalar quantity.