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

• A. (a), (b) and (c) are physical changes; (d) and (e)are chemical changes
• B. (d), (b) and (e) are physical changes; (a) and (c) are chemical changes
• C. (a), (b) and (e) are physical changes; (c) and (d) are chemical changes
• D. (a), (c) and (e) are physical changes; (b) and (d) are chemical changes

Answer 1

The correct option is D (a), (c) and (e) are physical changes; (b) and (d) are chemical changes

a) Evaporation of petrol is a physical change as no new product is formed only physical state changes.

b) Burning of Liquefaction of petroleum gas is a chemical change as new products are formed.

c) Heating iron rod to red hot is a physical change as no new product is formed; only temporary change (increase in temperature) occurs.

d) Curdling of milk is a chemical change as a new product in the form of curd is formed whose chemical composition is different from milk.

e) Sublimation of ammonium chloride is a physical process in which solid-state changes to gaseous one.

Hence the correct option is D.