This section gives definitions of the terms used in this module.
The following terms are used in this module:
- pH: A measure of the acidity or alkalinity of a solution. Aqueous solutions at 25ºC with a pH less than 7 are considered acidic, while those with a pH greater than 7 are considered basic (alkaline). pH values are commonly in the range of 1 to 14, though more extreme values, even negative values, are possible. When a pH level is 7, it is defined as 'neutral’.
- Aqueous: An aqueous solution is one in which the solvent is water. It is usually shown in chemical equations by appending ‘(aq)’ to the relevant formula. The word aqueous means pertaining to, related to, similar to, or dissolved in water.
- aw: Water activity or 'aw' is a measurement of the energy status of the water in a system. It is defined as the vapour pressure of water divided by that of pure water at the same temperature. Therefore, pure distilled water has a water activity of exactly 1.