The ionic compounds are salt and sodium bicarbonate. The covalent compounds are oil and cornstarch.
The ionic or covalent bond in the structure can be assessed in the laboratory by dissolving the compounds in the water.
The ionic compounds on dissolution will disintegrate into positive and negative ions.
The oil dissolving in the water will float onto it, thus the compound did not dissociate and has a covalent bond in the structure.
The cornstarch is a carbohydrate moiety and on dissolving in the water will be unable to disintegrate. The compound is composed of a covalent bond.
The salt on dissolving in water completely dissociates and becomes soluble. The compound disintegrates into the constituent ions. Thus, salt is an ionic compound.
Sodium bicarbonate is also an ionic compound, as it dissociates into the water.
The investigation question will be: Which of the following compound has an ionic and covalent bond?