Key terms & definitions

The amount of hydrogen ions, $H^+$, present in a given volume of solution.

The amount of hydrogen ions, $\mathrm{H^+}$, per unit volume of a solution. A higher hydrogen ion concentration gives a lower pH.

A fuel cell in which hydrogen reacts with oxygen, transferring chemical energy mainly as electrical energy and producing water.

A graph showing how river discharge changes over time; a storm hydrograph also displays rainfall.

A shortage of water in rivers, lakes, reservoirs or groundwater, often developing after prolonged below-normal rainfall.

A reaction in which water is added to break chemical bonds in a molecule.

Attracted to water; describes the water-facing region of an emulsifier molecule.

Repelled by water; describes the region of an emulsifier molecule that associates with oil.

Growing plants without soil, with their roots supplied with a water solution containing mineral nutrients.

A method of growing plants without soil, using water containing dissolved mineral ions.

A stable condition in which the inward effect of gravity is balanced by the outward pressure of hot stellar material.

A negatively charged ion with the formula OH⁻. Hydroxide compounds are included in these solubility rules, although hydroxides are not salts.

A negatively charged ion, OH⁻, supplied by an alkali in solution.

A negatively charged ion, $\mathrm{OH^-}$, consisting of an oxygen atom and a hydrogen atom bonded together.

The –OH group found in an alcohol molecule.

Practices that maintain cleanliness and help prevent disease, such as washing and safely handling waste.

Practices that maintain cleanliness and reduce the spread of pathogens, such as handwashing.

The god of weddings, whose unhappy presence at Orpheus and Eurydice’s marriage signals disaster rather than good fortune.

A song or poem addressed to a deity, usually celebrating their identity and deeds and sometimes asking for a blessing.

Words of praise or prayer addressed to God and set to music, usually arranged in verses.

Elite Macedonian infantry, also called shield-bearers, who were more mobile than the sarissa-bearing phalanx.

Publicity that builds up the importance and excitement of an event.

Deliberate exaggeration used for emphasis or effect.

Deliberate exaggeration for emphasis, not intended to be understood literally.

Deliberate exaggeration used for emphasis or effect, rather than as a literal factual claim.

An exaggerated statement used for emphasis or dramatic effect.

An extremely rapid, uncontrolled rise in prices that sharply reduces the purchasing power of money.

A clickable connection that takes a user to another page, website or piece of content.

A defect of vision in which light from a near object would come to a focus behind the retina, making near objects appear blurred.

Persistently high blood pressure.