Question

the burning of a piece of magnesium ribbon in air is a chemical change .explain.

Answer 1

2Mg + O2 = 2MgO
Thus when magnesium is burnt in air, it reacts with atmospheric oxygen and gives rise to the production of Magnesium Oxide. In this reaction a new chemical compound is formed and thus it is a chemical change.

Answer 2

Take a magnesium ribbon and burn it. It forms a white powdery substance and it mix with oxygen to form a magnesium oxide.
The formed reaction cannot be reversed.
The formed reaction is totally different from the original substance.
Hence this is a chemical change