Answer 1

Chemical reaction is the process in which atoms of some elements rearrange—that is, undergo a chemical change—to form a new product with different properties. This involves breaking of old bonds between the reacting atoms and making of new chemical bonds between the rearranged atoms.

For example, the burning of magnesium ribbon in air. In this reaction, magnesium ribbon, on heating, combines with oxygen to form a white powder of magnesium oxide, which is totally different in its properties from magnesium and oxygen.