what  is a chemical reaction
 

a reaction in which composition and chemical properties of a substance are changed and one or more new substances are formed is called a chemical reaction.

a reation in which chemical names are used.eg-Mg+0_{2 =MgO}

A chemical reaction occurs when two substances react chemically to form new substances with different chemical properties. A chemical reaction can also be called a chemical change.Original substances participating in a chemical reaction are called reactants and the new substance formed is called a product.
During a chemical reaction, substances undergo chemical transformation to form new substance.