Final answer:
NaNO₃ and CuSO₄ are soluble in water and are classified as electrolytes because they dissociate into ions in solution. Ca, Si, and CH₄ do not dissolve in water due to their chemical nature, with Ca being a metal, Si being a semiconductor, and CH₄ being a nonpolar molecule.
Step-by-step explanation:
Among the substances listed, NaNO₃ and CuSO₄ dissolve in water. NaNO₃ is a salt and when it dissolves in water, it dissociates into its ions, making it an electrolyte. This means that a solution of NaNO₃ will conduct electricity. Similar behavior is exhibited by CuSO₄, which also dissociates into ions when dissolved in water, indicating that it is an electrolyte as well.
Calcium (Ca) is a metal that does not dissolve in water under normal conditions. Silicon (Si) is a semiconductor material and does not dissolve in water. Methane (CH₄) is a nonpolar molecule and is insoluble in water, which is a polar solvent.
In a broader context, substances like NaCl and KOH are examples of inorganic compounds that are typically soluble in water due to their ionic nature and the solvation effect with water's large dipole moment. Nonpolar molecules like CH4 and elemental substances like Ca and Si don't dissolve significantly because they do not form strong interactions with water.