From Fig. and, it can be intuitively deduced that the accessible states for the smaller particle are significantly more than ones for the larger particle, and consequently, it possesses larger configurational entropy. Even though the residual space for the large particle in Fig. is larger than Fig. for smaller particle, the number of squares for the small particle in Fig. is significantly more than the larger particle in Fig. . Therefore, the system in Fig. has higher entropy than the system in Fig. , consequently, the configuration presented in Fig. is more favorable. This is called the entropy effect, and the quasi-gravitational force that attracts the larger particles to the surface of the wall is called the depletion force. Here, the question that comes to mind is: Is entropy larger when the larger disk is adjacent to the wall and the small disk is distributed in the residual space than when the larger disk is fixated in the middle of the box and the small disk is distributed in residual space? It is certainly higher when the larger disk is next to the wall as a portion of excluded volume locates outside of the box which leads to an increase in the number of accessible states for the smaller disk.