While lighting a candle, Paheli observed the following changes
(i) Wax was melting.
(ii) Candle was burning.
(iii) Size of the candle was reducing.
(iv) Melted wax was getting solidified.
Of the above, the changes that can be reversed are
Melting of wax is a physical change where the physical state of wax changes from solid to liquid. The melted wax that solidifies, can be changed to a liquid state on heating. These two are physical changes and thus, can be reversed.
● Burning of candle is a chemical change which involves breaking of chemical bonds in a process called combustion.
● The size of the burning candle reduces due to this change and cannot be reversed immediately.
● These two changes involve changes in chemical properties and thus cannot be reversed.