Combined Science key terms

The process of exposing an object to nuclear radiation. The irradiated object does not become radioactive.

Atoms of the same element with 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 varies with the potential difference across it.

In vitro fertilisation: a fertility treatment in which eggs are fertilised by sperm in a laboratory and an embryo is transferred into the uterus.

The unit of energy and work done. One joule is the work done when a force of one newton causes a displacement of one metre along its line of action.

An instrument that measures energy transferred, in joules.

A point where circuit branches meet and current can split or recombine.

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

Energy stored by a moving object. It depends on its mass and the square of its speed: $E_k = \frac{1}{2}mv^2$.

Energy stored by a moving object.

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 substance formed by the incomplete oxidation of glucose during anaerobic respiration in muscles.

A site where waste is disposed of by burying it in the ground.

Energy transferred when a substance changes state without changing temperature.

A light-dependent resistor: an electrical component whose resistance decreases as the light intensity reaching it increases.

A solution containing substances dissolved out of a solid material; in bioleaching, it contains dissolved metal compounds.

The rule that a system at equilibrium responds to a change in conditions in a direction that counteracts the change.

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

A hollow metal container with different surface finishes on its four sides, used to compare infrared emission when filled with hot water.

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

An assessment of environmental impacts across all stages of a product’s life, from obtaining raw materials to disposal.

An assessment of a product’s environmental impact throughout its life, from extracting raw materials to disposal, including transport and distribution at each stage.

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.

The amount of light reaching a given area per unit time.