PLEASE ANSWER AWARDING 50 POINTS FOR WHO EVER IS RIGHT: Kerry made some copper sulphate crystals. She wrote a description of what
she did.
I heated some dilute sulphuric acid in a beaker and added some copper
oxide to it.
I stirred the mixture until it became a clear blue colour. I added more
copper oxide until no more would react and then filtered the mixture into
a dish.
A black solid was left on the filter paper. I left the solution in the dish for a
week and saw that the liquid had evaporated and blue crystals were left.

question: Why did Kerry Filter the mixture?