Edexcel GCSE Combined Science key terms

An atom or group of atoms with an overall positive or negative electrical charge.

A strong electrostatic attraction between oppositely charged ions.

An equation showing only the species that change during a reaction, with both atoms and total electrical charge balanced.

Radiation that has enough energy to remove electrons from atoms, forming ions.

A regular arrangement of ions in a metal. The ions vibrate about fixed positions while electrons can move through the metal.

Exposure of an object or person to radiation from a source, without necessarily transferring radioactive material.

An atom of a particular element with a particular number of neutrons. Isotopes of the same element have the same number of protons but different numbers of neutrons.

The proportion of atoms in a sample that belong to a particular isotope, often expressed as a percentage.

A graph showing how the current through a component changes with the potential difference across it.

In vitro fertilisation: eggs are fertilised by sperm outside the body, and an embryo is then transferred into the uterus.

The SI unit of energy and work done. One joule is the work done by a force of one newton moving an object one metre in the direction of the force.

An instrument that measures energy transferred, in joules.

A point in a circuit where current can split between paths or where paths join together.

A temperature scale starting at absolute zero. A change of 1 K is the same size as a change of 1 °C.

The energy an object has because it is moving. It depends on its mass and the square of its speed.

A model that describes matter as particles in constant motion and explains its properties through their movement and arrangement.

A major group in biological classification, below domain in the three-domain system.

A light-dependent resistor whose resistance decreases as the light intensity falling on it increases.

The metal-ion-containing solution produced during leaching of an ore.

The principle that, when conditions affecting a system at equilibrium change, the equilibrium position shifts to counteract the change.

A plant such as a pea, bean or clover that can have nitrogen-fixing bacteria living in nodules on its roots.

Luteinising hormone: a hormone released by the pituitary gland that triggers ovulation.

An assessment of a product’s environmental effects across obtaining its raw materials, manufacturing it, using it and disposing of it.

An enzyme that joins DNA fragments together.

A device that detects when an object interrupts a light beam, allowing its motion to be timed electronically.

An instrument that uses visible light and lenses to produce a magnified image of a specimen.

A substance deposited in xylem cell walls that strengthens them.