Have you ever tried tasting a cut lemon? That sour taste is because lemon juice is an acid.


Ever noticed how Vinegar cleans a dirty utensil immediately? That vinegar is an acid. 


Let’s look at the definition of Acid

Formal Definition of Acid

Acid is a substance which produces H+ ions when dissolved in water.

For example:

In its aqueous solution hydrochloric HCl (aq) dissociates as: 

HCl (aq) ⎯⎯→ H+(aq) + Cl–(aq)


Some examples of acids are: 

  • Hydrochloric acid (HCl) - in gastric juice 
  • Carbonic acid (H 2 CO 3 ) - in soft drinks
  • Ascorbic acid (vitamin C) - in lemon and citrus fruits
  • Acetic acid in vinegar


Let’s look at how we identify acids by looking at its properties

Types of Acids

  • Organic Acids - Organic Acids are naturally occurring acids.
    • Acetic Acid is found in Vinegar
    • Citric Acid is found in Citrus fruits like lemon and orange
    • Lactic Acid is found in Curd
    • Oxalic Acid is found in Tomatoes


  • Mineral Acids - Acids prepared from Minerals of the Earth are called Mineral Acids.
    They are man-made acids
    • Hydrochloric Acid
    • Sulphuric Acid
    • Nitric Acid

Properties of Acids

  • Acids are Sour in Taste

  • Acids and Indicators



Color in acidic medium

Litmus Paper

Blue to Red



Methyl orange



Doesn’t change color. Remains yellow


  • Solutions of Acids conduct electricity

  • Acids are corrosive in nature and are capable of damaging many materials.
    This is also why acids are never stored in metal containers and are preferred to be stored in glass or ceramic containers which do not get attacked by the acid.
    Example - A drop of concentrated sulphuric acid (H2SO4) can burn through cloth.

  • Acids react with metals to form Hydrogen Gas
    Acid + Metal ⎯→ Salt + Hydrogen gas

  • Acids react with metal carbonates (and metal hydrogen carbonates) to form Carbon Dioxide Gas
    Acid + Metal Carbonates ⎯→ Salt + Carbon Dioxide + Water
  • Acid + Metal Hydrogencarbonates ⎯→ Salt + Carbon Dioxide + Water

  • Acid reacts with Base to form Salt and Water
    Acid + Base ⎯→ Salt + Water

  • Acid reacts with Metal oxides to form Salt and Water
    Metal Oxide + Acid ⎯→ Salt + Water

Some Properties of Acids-Teachoo.jpg

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo