saturated fatty acids don't have double bonds, but unsaturated do. Because the sat fat acids do not have these double bonds they pack together more easily, and have stronger intermolecular forces,eg .van der waals between them. so there generally solid. Whereas unsat fat acids have double bonds, therefore they have kinks and twists in the chains, less strong van der waals force between them and so liquid state. this is at room temp.
