Heating of copper sulphate crystals - Lab Work

To carry out the Heating of copper sulphate crystals and classify it as physical or chemical changes

Aim
To carry out the Heating of copper sulphate crystals and classify it as physical or chemical changes

Theory
Physical Change: These changes can be observed and take place without changing the composition of substances. There are no changes in chemical nature of substance. The changes which can be observed are like change in colour, boiling point, melting point, hardness, density, fluidity, rigidity etc. The interconversion of states of matter is also a physical change.

Chemical change: In this change, chemical reaction takes place and completely a new substance with different properties is formed. There are changes in chemical properties and composition of substance.
ex: Mg(s) + O2(g) → 2MgO(s)
Here, the chemical composition and properties of product MgO is totally different from its reactants Mg and O.

Chemicals Required
Copper Sulphate Crystals

Apparatus Required
Bunsen Burners, Boiling test tubes, Test tubes Holder

Procedure 


Step 1: Small amount of copper sulphate crystals is taken dry boiling test tube.

Step 2: Boiling test tube is hold with test tube holder and heated over flame on Bunsen burner.
Step 3: The colour of copper sulphate crystals is observed after heating for some time.
Step 4: The water droplets along the sides of the boiling tube is noted.
Step 5: The boiling tube is removed from the flame and cool.
Step 6: 2-3 drops of water on the sample of copper sulphate obtained after heating is added.

Observation
1. On heating the copper sulphate crystals, the colour changes from blue to white.
2. There are water droplets on the walls of the boiling tube.
3. On adding 2-3 drops of water white copper sulphate turns blue.

Inference
1. Copper sulphate crystals contain water of crystallisation (CuSO4.5H2O).
2. On heating, hydrated copper sulphate loses its water molecule and forms white coloured anhydrous copper sulphate.

               CuSO4.5H2O(s)   (heat)→     CuSO4(s)  +  5H2O(g)
                 (Blue coloured)              (White coloured)

3. On adding water anhydrous copper sulphate changes to hydrated copper sulphate.
4. It is a reversible chemical change.

Precautions
1. Keep the mouth of the test tube away from your face and also from other classmates.
2. Always use test tube holder while heating the test tube.
3. Take a small quantity of copper sulphate crystals.

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