would copper sulfate crystals grow better in water or only surrounded by air?
Copper sulphate crystals need to be surrounded by a saturated solution of copper sulphate if they are to grow. If you surround them with water they will dissolve; if you stand them in air nothing will happen - though I suppose if the vapour pressure of water in the air was very low they might effloresce (i.e. lose water of crystallisation).
