Not all viscous liquids are oils, and not all oils are viscous liquids. The distinction between the two terms lies in their composition and properties.
Viscosity refers to the resistance of a fluid to flow. A viscous liquid has a high resistance to flow and tends to be thick and sticky. While many oils exhibit viscosity, not all viscous liquids are oils. There are other substances, such as syrups, honey, molasses, and certain polymers, that can be viscous without being oils.
On the other hand, oils are a class of substances that are hydrophobic (repel water) and typically immiscible with water. Oils can be derived from various sources, including plants, animals, and minerals. They consist of long hydrocarbon chains or mixtures of hydrocarbons. Oils can exhibit a range of viscosities, from thin and low-viscosity oils like cooking oil to thick and highly viscous oils like heavy machine lubricants or motor oils.
In summary, while many oils are viscous liquids, not all viscous liquids are oils. The viscosity of a liquid depends on its internal molecular structure and interactions, while oils specifically refer to hydrophobic substances with varying viscosities.