Combination reaction. We will see the action of water on quick line. Apparatus required is a china dish beaker containing water in it, dropper, a quick line or calcium oxide. Take calcium oxide in a china dish. Add water with it with the help of dropper. Observe the reaction. Sings sound is produced during the reaction. The china dish becomes hot. So heat is evolved. It is an exothermic reaction. Slegged line or calcium hydroxide is produced. This is an example of combination reaction. Effects of heat on crystals of ferrous sulphate. Requirements for this experiment are ferrous sulphate, test tube, burner or spirit lamp. 10 milliliters of powdered crystal of ferrous sulphate in a test tube. Then we clamp the test tube to a stand and heat it with a burner or spirit lamp for 10 minutes. We note the changes in color of the substance in the test tube. Then we keep the hot test tube on an asbestos sheet. We observe the color of the substance in the test tube after cooling. We can say that on heating the pale green colored crystals of ferrous sulphate undergo decomposition. A mixture of ferric oxide Fe2O3, sulphur dioxide SO2 and sulphur trioxide SO3 are formed. A residue of brown color remains in the test tube. Displacement reaction. Reaction of copper sulphate solution on iron nails. Take iron nails free form rust. Clean it with sand paper and wash with water. Place the iron nail in copper sulphate solution for about 10 to 15 minutes. Remove the nail from the solution. Observe the change in the color of the nail. Before the reaction its color was steel green. After reaction it becomes reddish brown to light green after Fe plus iron center. So it is displaced. This is the example of displacement reaction. Double displacement reaction. Let us see the reaction between sodium sulphate and barium chloride. Requirements for the experiment are sodium sulphate. Barium chloride test tube. The color and appearance of both sodium sulphate that is NO2SO4 and barium chloride that is BA, CL2 are clear and transparent. Now take NA2SO4 on a test tube and BA, CL2. After reaction we observe white precipitate of barium sulphate. The compounds white precipitate of BASO4 and colorless NACl are formed by mutual exchange of ions. Therefore it is double displacement reaction.