A student wants to determine whether an unknown solid is an ionic compound. He puts some in water and finds that it does not dissolve. He says that this proves the solid is ionic. Which best evaluates the student's reasoning? He is incorrect, because water can dissolve ionic solids. The test proves nothing, because water dissolves all solids. He is correct, because polar liquids cannot dissolve ionic solids. The test proves nothing, because it only shows that the solid is a compound.