Heating drives off the water of hydration:
* Hydrated copper sulfate (CuSO₄·5H₂O) is a compound where copper sulfate molecules are bonded to five water molecules. This bonding is what gives the crystals their characteristic blue color.
* Heating the solution provides energy to break these bonds. The water molecules are released as steam, leaving behind anhydrous copper sulfate (CuSO₄).
* Anhydrous copper sulfate is white, powdery, and doesn't have the same crystal structure as the hydrated form.
How to obtain hydrated crystals:
To obtain hydrated copper sulfate crystals, you need to follow a different process:
1. Prepare a saturated solution of copper sulfate: This means dissolving copper sulfate in water until no more can dissolve at a given temperature.
2. Allow the solution to cool slowly: As the solution cools, the solubility of copper sulfate decreases. This forces the excess copper sulfate to crystallize out of the solution.
3. Filter and dry the crystals: The crystals are then separated from the remaining solution by filtration and allowed to air-dry.
In summary: Direct heating of a copper sulfate solution will dehydrate the crystals, leaving you with anhydrous copper sulfate. To obtain hydrated copper sulfate crystals, you need to carefully cool a saturated solution to induce crystallization.
