All else equal, entropy generally increases with larger molecules. There are more atoms in the larger molecule and so there is a higher potential for disorder since there are more random paths that the atoms can take. This concept is often presented like this: entropy can be thought of as a messy room. The more disarray (messiness) in the room, the higher the entropy. If you have more shirts and clutter (lots of atoms) in your room, your room will be more disordered (have higher entropy) than a room with less clutter.
