## Chemical Equations

Any equation which describes the change of reactants to products is called chemical reaction.
Reactant1+Reactant2+…………--->   Product1+Product2+………
In chemical equations reactants are placed on left hand side and products are placed on right hand side and arrow sign is placed between them. Direction of arrow shows the direction of reaction.
Example: chemical equations in words.
Magnesium + Oxygen {Reactants} .------->  Magnesium-Oxide {Product}

### Writing a Chemical Equation by using Chemical Formula:

In it we use symbols instead of words to write a chemical equation.
Example: Mg + O2 .-----> MgO

#### 1.    Unbalanced Chemical Equation:

Equation in which number of atoms on reactant side is not equal to number of atoms on product side, means mass is not same on both sides.
Example: Mg + O2 -----> MgO
Fe +  H2O -----> Fe3O4 + H2

#### 2.    Balanced Chemical Equation:

Equation in which number of atoms on reactant side is equal to number of atoms on product side, means mass is same on both sides.
Example: 2Mg + O2 ----> 2MgO
3Fe + 4H2O -----> Fe3O4 + 4H2

### Writing Symbols of Physical State:

Reactants and products are written with their physical state to make equation more informative.
 Physical State Notation Gaseous (g) Liquid (l) Aqueous (aq) Solid (s)
Example: 3Fe (s) + 4H2O (g) ----> Fe3O4 (s) + 4H2 (g)
·       Example of reactions with reaction condition like pressure, temperature, catalyst etc.