Chemical Reaction

The process in which two or more substance combine to form new substance with different properties is called a chemical reaction. The substances that reacts, are called as reactants and the substances that are formed are called products.
e.g. Carbon reacts with oxygen to form carbon dioxide.

Chemical Equation

The representation of chemical reaction in the form of symbols and formulae is called as chemical equation.
For example:
           C+O₂     →     CO₂

Types of Chemical Reaction

Combination Reaction

The chemical reaction in which substances combine to form new product is called a combination reaction.
For example:
           C+O₂     →     CO₂

Decomposition Reaction

The chemical reaction in which single reactant breaks to form more than one product is called decomposition reaction. Most of the times decomposition is carried out by heating, such a decomposition reaction is called thermal decomposition reaction.
For example:
                              Heat
          CaCO₃(s)     →     CaO(s) + CO₂(g)
           (Limestone)            (Quicklime)

                          sunlight
          2AgCl      →     2Ag(s) +Cl₂(g)
Activity: Take a dry boiling tube and add 2g of ferrous sulphate crystals in it. Heat the tube over flame of a burner. You can observe the green color of crystal changes and you can smell the odour of burning sulphur.

                                Heat

           2FeSO₄(s)     →     Fe₂O₃(s) + SO₂(g)+ SO₃(g)
           (Ferrous Sulphate)             (Ferric Oxide)

Displacement Reaction

In a reaction, when an element displaces another element from its compound, it is called displacement reaction.

• Activity: Take 3 iron nails and clean them by rubbing with sandpaper. Take 2 test tubes and mark them as (A) and (B). In each test tube add about 10 ml Copper Sulphate Solution.
• Tie 2 iron nails with thread and immerse them in copper sulphate solution in test tube B for 20 minutes. Keep one iron nail aside for comparison. After 20 minutes, take out iron nails from copper sulphate solution. Compare intensity of blue color of copper sulphate solution in test tubes (A) and (B). You can observe that slowly the blue color of copper sulphate solution fades away and iron nail becomes brownish in color. This is because the iron atoms displaces the copper atoms from the copper sulphate solution.
• Similarly if zinc granules are added in copper sulphate solution, zinc atoms displaces copper atoms.

           CuSO₄(aq) + Zn(s)     →     ZnSO₄(s) + Cu(s)
           (Copper Sulphate)                               (Zinc Sulphate)

           CuCl₂(aq) + Pb(s)     →     PbCl₂(aq) + Cu(s)
           (Copper Chloride)                               (Lead Chloride)

Double Displacement Reaction

• The chemical reaction in which two different atoms or group of atoms (ions) are exchanged, is known as double displacement reaction.
• Take about 3 ml of sodium sulphate solution in test tube. In another test tube take 3 ml of barium chloride solution. Mix the two solutions. A white insoluble BaSO4 is formed. Other product formed is sodium chloride which remains in the solution.

           Na₂SO₄(aq)     +     BaCl₂(aq)     →     BaSO₄(s)     +     2NaCl(aq)
           (Sodium Sulphate)             (Barium Chloride)           (Barium Sulphate)         (Sodium Chloride)

Exothermic Reaction

The chemical reaction in which heat is released is called exothermic reaction.
Activity: Take a small amount of quicklime in a beaker and slowly add water to it. Check the temperature of beaker. The temperature of beaker increases. It is because Calcium oxide reacts vigorously with water producing slaked lime and releases large amount of heat. Therefore this is a exothermic reaction.

           Na₂SO₄(aq)     +     BaCl₂(aq)     →     BaSO₄(s)     +     2NaCl(aq)
           (Sodium Sulphate)             (Barium Chloride)           (Barium Sulphate)         (Sodium Chloride)

Burning of Coal and Natural gas are also exothermic reactions
           C+O₂     →     CO₂

           CH₄(g)     +     2O₂(g)     →     CO₂(g)     +     2H₂O(g)

In cells of our body glucose combines with oxygen and produces energy leading to exothermic reaction
           C₆H₁₂O₆(aq)     +     6O₂(aq)     →     6CO₂(aq)      +     6H₂O(l)   +     Energy
           (Glucose)

Endothermic Reaction

The chemical reaction in which heat is absorbed then such a reaction is called endothermic reaction.
Activity: Take about 2 g barium hydroxide in a test tube. Add 1 g of ammonium chloride and mix with the help of a glass rod. Touch the bottom of the test tube with your palm.

                             sunlight
          2AgBr(s)      →     2Ag(s)    +     Br₂(g)

Redox Reaction

Addition of oxygen or removal of hydrogen during a reaction is called oxidation. Loss of electrons is oxidation reaction. Addition of hydrogen or removal of oxygen during reaction is called reduction. The chemical reaction in which oxidation and reduction takes place simultaneously is called as redox reaction.
Oxidation Reaction
                                        Heat
           2Cu     +     O₂      →     2CuO

Reduction Reaction
           H₂     +     Br₂     →     2 HBr
Redox Reaction

Redox Reaction

Keywords: Types of Chemical Reaction, Combination Reaction, Displacement Reaction, Decomposition Reaction, Oxidation, Reduction, Redox Reaction.

Related articles

Reaction of metals with oxygen
Physical properties of metal and non-metal
Periodic Table and Periodic Trends
States of matter
Solution