Acid, Bases and Salts

Acid and Bases

Substances which taste sour are acids. Substances which taste bitter and are slippery to touch are bases. But some substances do not have taste. So how do we classify them as acids or salts? These are classified with the help of indicators.


Natural Indicators

The substances which are used to test whether a substance is acidic or basic in nature are known as indicators. There are certain naturally occurring indicators which are used to test the acidity or basicity of a solution. For example, litmus paper obtained from lichens, turmeric and China rose are some of the natural indicators. Refer to the figures below to understand the changes in acidic or basic solution.


Acids turn blue litmus red. Bases turn red litmus blue.



As the name suggests, neutralization in simplest terms means the neutralising effect of acids when poured into bases or vice versa.

Let us take Hydrochloric acid for an acid, Sodium Hydroxide for a base and Phenolphthalein for an indicator to understand the neutralizing effect.

Remember that all three are colorless.


Pour few drops of Phenolphthalein to Hydrochloric acid. We obtain a colorless solution.


Start adding Sodium Hydroxide drop by drop to the above solution, until you obtain a pink colour.


Now again add Hydrochloric acid drop by drop to the pink solution, you will find that the solution again turn colorless.

Can you infer what is happening here?

We can draw two inferences from above.

  • Phenolphthalein gives pink colour when the solution is basic and remain colourless when solution is acidic.
  • When acidic and basic solutions are mixed in suitable quantity, they destroy the acidic and basic nature of the solution.

Reaction below is known as neutralization reaction and the substance produced is known as salt.


To learn more about acids, bases, salts and their effect on indicators, download Byju’s the Learning App. We also have all the Acid, Bases and Salts – related problems sorted out with the NCERT solutions.

Practise This Question

Find the roots of the equation 5x26x2=0 by the method of completing the square.