Question 2
In activity 3.1.2 the liquid that passed through the filter paper was blue. What does that colour show?
The right answer is the one marked above.
The copper sulphate dissolved and kept its identity. Blue is what copper sulphate looks like. Seeing it in the filtrate means the compound is still there, still itself, merely dissolved.
This is the point the whole definition of a mixture rests on. Had grinding produced a new substance, or had the water destroyed the copper sulphate, nothing blue would have come through the paper.