Acids, Bases and Salts



  • Acids are those  substances which gives H+ inside a solution.
  • Ph 1 to Ph 3 are considered as Strong Acids.
  • Ph 4 to Ph 6 are considered as weak acids.
  • Acidic substances like lemon juice , vinegar etc.. tastes sour.
  • Hydrochloric acids, nitric acids are some  examples of  strong acids.
  • Acetic acids, phosphoric acids are some examples of weak acids.


  • Bases are those substances which give hydroxide ions( OH-) inside a solution.
  • Ph 8 to Ph 14 are considered as bases.
  • Ph 8 to 10 are weak bases.
  • Ph 11 to 14 are strong bases.
  • Bases tastes bitter and are are soapy in nature.
  • Sodium hydroxide , calcium hydroxide are some examples of strong bases.
  • Ammonia, hydrogen sulphide are some examples of weak bases.


  • Substances which are used to identify another substance acidic or basic nature are termed as Indicators.
  • Indicators change their colour when exposed to a acid or a base.
  • Turmeric, China Rose are some examples of Natural Indicators.

Litmus Paper:

  • Litmus is the most commonly used natural indicator.
  • It is extracted from Lichens.
  • It turns red when added to an acidic solution.
  • It turns blue when added to a basic solution.
  • The solutions which does not change it’s colour are known as neutral solutions.
  • Neutral Solutions have a Ph 7.

Acid Rain:

  • Biological processes on land lead to the formation of harmful gases.
  • Acid rain is caused due to sulphuric acid and nitric acid.
  • When normal rain falls, these harmful gases get mixed with the rain water and thus forms acid rain.
  • Acid rain is also harmful to the health of humans.
  • Acid rain can travel longer distances.
  • Acid rain is very harmful for buildings, monuments, forests , aquatic life etc..


  • The reaction which takes place between acids and bases to give salts and water is known as Neutralisation Reaction.
  • For example: when hydrochloric acid is mixed with sodium hydroxide it gives sodium chloride (salt) and water.
  • Hydrochloric acid is present on our stomach and it helps in the digestion of our food..
  • If we suffer from indigestion then we take antacids such as milk which contain magnesium hydroxide that neutralises the effect of excessive acid.
  • Acids of ant bites can be neutralised by rubbing moist baking soda.
  • Excessive acids in soil is treated with bases like quick lime or slaked lime.

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