CuSO4 Crystals, Yum

Crystal Revision

These are COPPER SULPHATE CRYSTALS (CuSO4)

Method:

Part 1:

1. Weigh 7g of copper sulphate powder into a 250ml beaker using an electric balance
2. Collect 100ml of copper sulphate into a second beaker
3. Add 7g of copper sulphate to the solution and stir (to make solution saturated)
4. Heat beaker and stir to dissolve the solid powder (solution now supersaturated)
5. Pour the warm solution into the clean petri dish until 2/3 full and leave overnight (time is required in order for the solution to cool and solidify into crystals. The solution is now less but still supersaturated)
6. Cover the rest of a solution with a cardboard lid

Part 2:

7. Choose 2 seed crystals and place them on clean paper. (Shape/figure is more important than size as it is the template for the final crystal) Measure and draw one crystal. DO NOT TOUCH THE CRYSTAL (copper sulphate is poisonous and thus potentially harmful)
8. Tie a slip knot around the other seed crystal with cotton thread
9. Suspend the thread through the cardboard lid
10. Tip the remaining crystals back into the solution. You may need to scrape the crystals with a spatula (Crystals may have solidified onto the bottom of the dish)
11. Heat the solution until ALL of the solid has dissolved (This is increasing the saturation of the solution again)
12. COOL the solution in a shallow, cold water bath (otherwise the suspended seed crystal will melt)
13. Hang the crystal in the cool solution and leave to grow

Explanation:

As the supersaturated solution cools, the excess copper sulphate will solidify onto the seed crystal. Shape is maintained though the size will increase. Particles basically join evenly to the template as opposed to falling to the bottom of the beaker.
-Crystals grow by adding single layers of molecules at a time
-As the water cools and evaporates, the solid is forced out make these layers
-Crystal shape depends on the arrangement of atoms

Definitions:

Solution: Mixture of substance dissolved into another, solvent + solute = solution

Solvent: Does the dissolving (usually liquid, H2O)

Solute: Is dissolved (CuSO4 powder)

Unsaturated solution: Where the solution can hold more than what is dissolved into it

Saturated solution: Where the solution is holding exactly what it can. Adding excess will result in solid falling to the bottom, but solution itself remains saturated.

Supersaturated solution: Where excess solute is dissolved into the solution. It requires heat. When cooled, particles will be forced out of liquid and re-solidify.