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Chemistry vocabulary · Acids, Bases and Salts

Indicator

Meaning in chemistry, with examples

nounCore term

In chemistry, indicator means: A substance that changes color at a certain pH or at the end of a reaction, used to show when a titration is complete. Phenolphthalein and methyl orange are common examples.

In Turkish: indikatör, belirteç

How it is used

Used in titrations and quick pH checks. You add a few drops of indicator and watch for the color change. Phenolphthalein is colorless in acid and pink in base; universal indicator shows a range of colors.

Example sentences

  1. Add two or three drops of phenolphthalein indicator to the flask.

  2. Choose an indicator that changes color close to the equivalence point.

Common collocations

  • add indicator
  • acid–base indicator
  • universal indicator
  • color change
  • titrationA method for finding the unknown concentration of a solution by adding a solution of known concentration from a burette until the reaction between them is just complete.
  • endpointThe point in a titration where the indicator changes color or the signal changes sharply, showing that the reaction is complete and you should stop adding titrant.
  • pHA scale, usually from 0 to 14, that shows how acidic or basic a solution is. Below 7 is acidic, 7 is neutral at 25 °C and above 7 is basic; it equals −log[H⁺].
  • acidA substance that releases hydrogen ions (H⁺) in water or, more generally, donates protons. Its water solutions have a pH below 7 and turn blue litmus paper red.
  • baseA substance that accepts protons (H⁺) or releases hydroxide ions (OH⁻) in water. Its solutions have a pH above 7 and turn red litmus paper blue.

More terms: Acids, Bases and Salts

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