Which one of the following processes involve chemical reactions?
(A) Storing of oxygen gas under pressure in a gas cylinder
(B) Liquefaction of air
(C) Keeping petrol in a china dish in the open
(D) Heating copper wire in presence of air at high temperature
A physical change is the one in which the chemical properties of a substance do not change .
No chemical change is observed when we store oxygen gas under pressure, or during liquefaction of air or when petrol is kept open in a china dish.
However, when we heat a copper wire in the presence of air, copper oxide is formed .
The reaction is as follows:
So, the correct option is (d) heating copper wire in presence of air at a high temp