Question

what is a chemical reaction ?

Answer 1

a reaction in which reactants react together to form two or more products

Answer 2

Chemical reaction is defined as the process which leads to transformation of chemical substances from one form to another. In a chemical reaction the substances undergoing transformation are called reactant and the new substances that are formed are called products. 

For example A + B ―> C + D represents a chemical reaction in which reactants A and B undergo transformation to form products C and D.