A student is given four solid samples labeled W, X, Y and Z. She is told that the solids could be gold, lead (II) sulfide, silicon dioxide (quartz) and iodine. The results of her investigation are: a) W is a good electrical conductor while X, Y and Z are not b) When the solids are hit with a hammer, W flattens out, X shatters, Y is smashed into a powder and Z is not affected c) When the solids are heated with a Bunsen burner, Y sublimes but X, W and Z do not melt d) In treatment with 6M HNO3, X dissolves but there is no affect on W, Y or Z.
On the basis of these test results, identify the solids. (Show your reasoning)