Indicators are substances which possess measurable and observable characteristic which can be used to depict a the acidic or alkaline nature of a substance.
Indicators may be natural, those which exists naturally in nature such as litmus or turmeric.
Indicators such as Phenopthalein or Methyl orange are artifical indicators as they are obtained through laboratory preparation.
Blue litmus paper turns red when dipped into an acid while Red litmus turns blue when in contacts with a base.
Hence, indicators helps to know when a change in pH value of solution occurs.
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