We did this experiment in the lab.We had to prepare crystals of pure copper sulfate from a given impure sample of blue vitriol(powder). So my teacher started with shaking the sample with water and then added a few drops of dilute sulfuric acid to it. It was then heated to crystallization point and then cooled and the pure crystals of CuSO4 separated out. 1) Why are we adding Sulfuric acid? my teacher told me it is to prevent the hydrolysis of CuSO4. But how does that happen? 2) The crystallization point: I did a little reading about this but I'm not very clear. So when it's heated the solution will form stable clusters and this is called nucleation. But i am unable to understand how this happens. And then we just cool it and the crystal keeps building? Can someone please explain? And what is the liquid that's finally left behind after cooling when we separate the crystals out?