what are the indicators? write the examples of natural and chemical indicators
Answers
Indicators are chemical compounds that tell us whether a substance is acidic or basic by changing its colour. When added to an acidic solution or a basic solution, indicators change their colour and this change in colour is different for the acids and bases. The indicator thus help us to decide whether a given solution is acidic or basic in nature.
The indicators that are obtained from plants are known as natural indicators.
Examples – Turmeric, china rosa, red cabbage and grape juice.
Some flowers such as the hydrangeas can also determine whether a substance is acidic or basic. Hydrangeas turn blue if the soil is acidic, purple if the soil is neutral and pink if the soil is basic. The colour intensity depends on the amount of acid and base present in the soil.
Universal indicators are a mixture of organic dyes that give different colours at different concentrations of hydrogen ions in solution.
Example – pH paper or solution
Chemical indicator ;
, any substance that gives a visible sign, usually by a colour change, of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution. An example is the substance called methyl yellow, which imparts a yellow colour to an alkaline solution. If acid is slowly added, the solution remains yellow until all the alkali has been neutralized, whereupon the colour suddenly changes to red.