Basics of chemical reactions and chemical equations.

Chemical Change

The change which give rise to new substances with new properties that are totally different from the starting matter.

2H₂ + O₂     ———> 2H₂O

Chemical changes are normally accompanied by the following changes:-

1. change in state

2. Change in colour

3. Change in temprature

4. Evolution of gas

Chemical reaction

Representation of a chemical change in terms of reactants involved, various conditions and the products formed.

Chemical equation

The short representation of chemical reaction with the help of symbols of elements or the chemical formulae of compounds.

For example:-

                Zn + H₂SO_{4              ———>}    ZnSO₄   + H₂

Zinc + Sulfuric Acid         ———>  Zinc Sulfate + Hydrogen

Important terms in chemical Equation

1. Reactants:- The substances (elements or Compounds) that take part in reaction are called reactants. These are written on the left side (LHS) of a  reaction and a plus sign can be used if the reactants are more than one. As shown below:-

                Zn + H₂SO_{4                  ———>}                                              ZnSO₄   + H₂

2.Products :- These are the substances formed at the end of reaction. These are written on the right hand side of the chemical equation and the plus sign can be used if the products formed are more than one. As shown below.

Zn + H₂SO_{4                           ———>}                                     ZnSO₄   + H₂

The arrowhead:- it points towards the products and also towards the direction of the reaction.

Zn + H₂SO_{4                                 ———>}                               ZnSO₄   + H₂