Oil and water are known for their incompatibility due to their different molecular structures. Water is a polar molecule, meaning it has a positive and a negative end, which allows it to form hydrogen bonds with other water molecules. In contrast, oil is non-polar and does not have charged ends, preventing it from mixing with water. This difference leads to the formation of distinct layers when oil and water are combined. When oil is added to water, it floats on top because it is less dense. This separation occurs because the water molecules are more attracted to each other than to the oil molecules. As a result, emulsifiers are often used in cooking and food production to help mix oil and water, creating stable mixtures like mayonnaise or salad dressings.