question_answer 58)

  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:

  (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 CO2and H2O. (c) Heating of an iron rod to red hot is a physical change. (d) Curdling of milk is a chemical change because in the conversion of milk to curd, new chemical substances are formed. (e) It is a physical change, because solidvapours and no new chemical substance is formed.