Question

Which of the following is not a physical change?

Options

• Boiling of water to give water vapour

•  Melting of ice to give water

• Dissolution of salt in water

• Combustion of Liquefied Petroleum Gas (LPG)

Answer 1

Combustion of Liquefied Petroleum Gas (LPG)

Explanation - 

Boiling of water to give water vapour, melting of ice to give water and dissolution of salt in water are all examples of physical change, as in any of the three processes there is only change in state and the chemical composition of the compound is not changing. Whereas when liquified petroleum gas is burnt in air, it is actually undergoing a chemical reaction with oxygen gas present in the air and as a result of which two new products water and carbon dioxide are formed. Therefore, option 4 is an example of chemical change.