Final answer:
Unsaturated fats contain at least one double bond between carbon atoms. Monounsaturated fats have one double bond, and polyunsaturated fats have two or more double bonds, affecting their properties and state at room temperature.
Step-by-step explanation:
Unsaturated fats are fats that contain at least one double bond between carbon atoms within the fatty acid chain. There are two types of unsaturated fats: monounsaturated fats, which have a single double bond, and polyunsaturated fats, which contain two or more double bonds. The presence of double bonds means that these fats are not saturated with hydrogen, hence the term "unsaturated."
For instance, a monounsaturated fatty acid has one point of unsaturation or double bond, whereas a polyunsaturated fatty acid possesses multiple double bonds. These double bonds alter the geometry and physical properties of the fat molecules, causing them to be liquid at room temperature, unlike saturated fats that tend to be solid.