Question

Which among the following are physical or chemical changes?

(a) Evaporation of petrol

(b) 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

Answer 1

(a), (c) and (e) are physical changes. 

(b) and (d) are chemical changes

•  (a) Evaporation of petrol is a physical change because no new chemical substance is formed. 
• (b) Burning of LPG is a chemical change because on burning, LPG forms CO₂ and H₂O. 
• (c) Heating of an iron rod to red hot is a physical change.