Key terms & definitions

Force acting normally per unit area on a surface, produced in a gas by particle collisions with that surface.

The force exerted per unit area by gas particles colliding with the walls of their container.

The production of a gas, which can be followed by counting bubbles or measuring the volume collected.

Equipment that removes a pollutant from a gas stream by bringing the gas into contact with a reacting material.

Equipment that removes pollutants from waste gases, for example by reacting acidic sulfur dioxide with an alkaline material.

A graduated device whose plunger moves as gas enters, allowing the gas volume to be read from its scale.

An instrument with a movable plunger used to collect and measure the volume of a gas.

A procedure that identifies a gas by a characteristic observable result.

The calf muscle at the back of the lower leg, used in movements such as running and jumping.

The opening through which molten metal enters a mould cavity from a runner.

A residential development with controlled entry, usually enclosed by walls or fences.

A fortified building controlling an entrance to a castle or town.

A media owner or professional who influences what material is published or broadcast and how it is presented.

A person, such as an editor, owner or senior journalist, who influences which stories are selected for publication.

Drawing fabric together along threads to shorten an edge and form small, soft folds.

A Second Vatican Council document, issued in 1965, about the Church in the modern world. Paragraph 26 teaches that everyone must have access to the necessities of a truly human life.

A measure used to specify material thickness, particularly for sheets or films. Check how the supplier expresses it.

Pressure measured relative to atmospheric pressure; it is zero when the pressure equals atmospheric pressure.

The leader of a regional division of the Nazi Party, called a Gau.

A mesh placed on a tripod to support a vessel above a Bunsen burner and spread the heat.

A Vedic prayer in Rig Veda 3.62.10 addressed to Savitr, asking that divine light inspire and guide our minds.

A movement campaigning openly against discrimination towards gay people and for freedom, visibility and equal rights, which expanded rapidly after Stonewall in 1969.

A geographical reference book containing information about places and their inhabitants.

The value of goods and services produced within a country over a year, divided by its population. It indicates average economic output per person, not each person's actual income.

The German Democratic Republic: communist East Germany, established in 1949 and closely controlled by the Soviet Union.

A toothed wheel that turns about an axle and can transmit a turning effect to another gear.

A toothed wheel that meshes with another toothed component to transmit movement and force.

For a simple gear pair, the number of teeth on the driven gear divided by the number on the driver gear.

Also called Gehenna; a state or place of punishment after death, understood by many Jews as temporary purification rather than everlasting torment.

A detector in which incoming ionising radiation causes electrical pulses that can be counted.