Why does oil and water refuse to mix together?

Oil and water don't mix because of their molecular structures and how they interact with each other. Water molecules are polar, meaning they have a slight positive charge on one end and negative on the other, which causes them to form strong hydrogen bonds with each other. Oil molecules are nonpolar, meaning they have no such charge separation. When you try to combine them, water molecules are so strongly attracted to each other that they essentially exclude the oil molecules, forcing them to clump together separately. This follows the chemical principle "like dissolves like," meaning polar substances mix with polar substances and nonpolar with nonpolar. The energy required to break water's hydrogen bonds and insert oil molecules simply isn't available at room temperature.