Question

.The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it exist as a liquid. When it comes out from the cylinder it becomes a gas (Change – A) then it burns (Change – B). The following statements pertain to these changes. Choose the correct one.

Process – A is a chemical change.

Process – B is a chemical change.

Both processes A and B are chemical changes.

None of these processes is a chemical change

Answer 1

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$\tt\blue{★}$ The correct answer is (ii) 'Process – B' is a 'chemical change'.

Explanation: The gas we use in the 'kitchen' is called 'Liquefied petroleum gas' (LPG). In the 'cylinder', it exists as a 'liquid'.

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• Change A is physical change - In this change, the liquefied gas changes it states from liquid to gas and hence no new substance are formed.

• Change B is chemical change:- Burning produces new substance and hence the reaction can't be reversed back.

⠀⠀Burning

Gas $\sf{⟹}$ CO2 + heat + other substance.

Hint :- In process A, there are no new substances formed. In process B, there are new substances formed like carbon dioxide, heat, light, etc.

Answer 2

Answer:

Process A is a physical change because no new substance is formed. The LPG in cylinder is in liquid form because of high pressure. When it comes out from the cylinder, it turns into a gaseous form. Thus, it is a physical change