Final answer:
The entropy of a substance is influenced by its structure. For molecules, greater numbers of atoms increase the number of ways in which the molecules can vibrate, leading to a higher entropy.
Step-by-step explanation:
The entropy of a substance is influenced by the structure of the particles (atoms or molecules) that comprise the substance. For molecules, greater numbers of atoms increase the number of ways in which the molecules can vibrate and thus the number of possible microstates and the entropy of the system. The two types of horizontal arrangements of fuels mentioned in the question are topical and sub-surface. These are arrangements that describe how fuels can be stored or found in layers upon the Earth's surface or beneath it. Topical fuels refer to deposits that are on the surface of the ground or the seabed.