Final answer:
The separation of Potassium nitrate, naphthalene, and zinc oxide can be achieved through their differing solubility and melting point properties, which are the most relevant for separation processes.
Step-by-step explanation:
The properties that will help in the separation of Potassium nitrate, naphthalene, and zinc oxide are mainly solubility and melting point. The solubility of Potassium nitrate in water is high because all nitrates are soluble, making it easy to separate from the other two substances when mixed in water.
Naphthalene, which is a covalent compound, does not dissolve well in water but can be separated based on its sublimation property because it transitions directly from a solid to a gas when heated. Zinc oxide has different solubility and melting point properties compared to the other two, which can also be exploited for separation. Conductivity is less relevant in this context unless the separation process involves an electrical current.