Indicators
When an Corrosive substance which has a pH lower than 7. Acidity is caused by a high concentration of hydrogen ions. is dissolved in water we get an acidic solution. When a A substance that reacts with an acid to neutralise it and produce a salt. dissolves in water it is an A base which is soluble in water. and makes an alkaline solution. If a solution is neither acidic nor alkaline it is neutral. Pure water is neutral, and so is A liquid fraction from crude oil, also called kerosene, and containing alkanes (saturated hydrocarbons)..
Indicators are substances that change colour when they are added to acidic or alkaline solutions. Universal indicator is the indicator most commonly used in the laboratory.
The pH scale
The chemical properties of many solutions enable them to be divided into three categories 鈥 acidic, alkaline and neutral solutions.
The Scale of acidity or alkalinity. A pH (power of hydrogen) value below 7 is acidic, a pH value above 7 is alkaline. scale is used to measure acidity and alkalinity:
- solutions with a pH less than 7 are acidic
- solutions with a pH of 7 are neutral
- solutions with a pH greater than 7 are alkaline
If universal indicator is added to a solution it changes to a colour that shows the pH of the solution. Universal indicator is a mixture of a variety of other indicators and can be used to measure the approximate pH of a solution. A more accurate value can be obtained using a pH probe.