Question

Which of the following is not a physical change?
1. Boiling of water to give water vapour
2. melting of ice to give liquid water
3. Dissolution of salt in water
4. Combustion of Liquefied Petroleum Gas (LPG)

Answer 1

Correct Answer - Option 4 : Combustion of Liquefied Petroleum Gas (LPG)

The correct answer is Combustion of Liquefied Petroleum Gas (LPG)

• Chemical change: In this process chemical composition of the original matter changes.
  • New substances having different properties and different chemical compositions are formed.
• Like Combustion of Liquefied Petroleum Gas (LPG), as the substance formed changes chemically and cannot be turned back into LPG.
• Other examples: Rusting of an iron rod, burning of fuel, electrolysis of water, photosynthesis, ripening of fruits, etc.

• Physical change: It is usually a reversible change in the physical properties of a substance.
  • It affects the physical properties like colour, hardness, density, melting point, etc. of matter.
  • It will include:
  1. Boiling of water to give water vapour.
  2. Melting of ice to give liquid water.
  3. Dissolution of salt in water.
  • All these are reversible changes.