Profile
Settings
Refer your friends
Sign out
Answer: An indicator is a substance that changes its colour when put in an acidic or basic medium. An indicator shows different colours in an acidic medium and different colours in a basic medium. There are three types of indicators.
- Natural indicators
- Artificial indicators
- Old factory Indicators
Natural indicators
The indicators which occur in the environment naturally are known as natural indicators. Example: Litmus, turmeric, curry powder, beetroots and onion.
Litmus: Litmus is obtained from lichens and is mixed with water, making a water-soluble dye and then absorbed onto a paper strip. The natural colour of litmus paper is purple. Red litmus paper will turn blue in basic solution, and blue litmus will turn red in acidic solution.
Artificial indicators
The indicators are obtained through some chemicals but not naturally. They are prepared in labs. Example: Phenolphthalein and methyl orange.
Phenolphthalein:- It is a water-soluble dye which is purple. It is used for the test of acid and base. If added to the acidic medium, it turns colourless, and in the basic medium, it turns into light pink colour.
Old factory indicators
Olfactory indicators do not show any colour change but rather show a change in smell when added to an acidic, basic medium. The smell changes depending upon the nature of the medium. Example: Vanilla extract, onion and clove oil.
Onion extract:- onion extract can be made by adding schooled onion in boiling water. It shows the change in smell in acidic and basic mediums. When added to acid, it gives a pungent smell, and when added to a primary medium, it remains odourless.
Universal indicator
A universal indicator is a pH indicator, and it is a mixture of several indicators. It is used to measure the approximate pH of a solution. A universal indicator is added to the solution, and the colour changes according to the nature of the solution. The change in colour shows how strong or weak the acid or the base is. After the colour change, the moisture is matched with the pH scale, and the colour shows approximate pH.
