Question

Which among the following are physical or chemical changes? (a) Evaporation of petrol (6) Burning of Liquefied Petroleum Gas (LPG) (c) Heating of an iron rod to red hot (d) Curdling of milk (e) Sublimation of solid ammonium chloride

September 7, 2024

Answer

Change	Type of Change	Reason
(a) Evaporation of petrol	Physical Change	Only a change in state (liquid to gas), no new substance is formed.
(b) Burning of Liquefied Petroleum Gas (LPG)	Chemical Change	LPG undergoes combustion, producing new substances like CO₂ and H₂O with heat release.
(c) Heating of an iron rod to red hot	Physical Change	The iron rod changes color due to heat but remains the same substance.
(d) Curdling of milk	Chemical Change	Milk proteins undergo chemical changes, forming new substances (curd).
(e) Sublimation of solid ammonium chloride	Physical Change	Ammonium chloride changes from solid to gas without forming a new substance.

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