Final answer:
Oil and water remain separate because oil is nonpolar.
Step-by-step explanation:
When oil, such as olive oil, is combined with water, they remain separate and do not dissolve.
Oil is nonpolar, meaning it does not have an electric charge and does not easily mix with polar substances like water.
This is due to the difference in polarity between oil and water molecules.
Learn more about Polarity of oil and its interaction with water