GCSE CHEMISTRY - What is an Alkali? - What is a Base?

What is an Alkali?

An alkali is any substance that produces OH^- ions in water
(compare this with the definition of an acid).
OH^- ions are called hydroxide ions (see examples).

Alkali is pronounced like alcohol, with 'lie' at the end instead of 'hol'.

What is a Base?

A substance which will neutralise an acid,
but does not dissolve in water, is called a base.
For example,
copper(II) oxide, iron(II) oxide and zinc carbonate are bases,
they do not dissolve in water
(see salts made from bases or carbonates).

Any base that dissolves in water is called an alkali.
For example, sodium hydroxide,
potassium hydroxide and sodium carbonate are alkalis.

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