The relationship between wettability and surface geometric structure of modified silica particles and glass plates was investigated. Surface modification was performed by the autoclave method with 1-dodecanol to control the surface wettability. The preferential dispersion test proved that wettability varied at a surface modification ratio of 20%, which coincided with the changing point of the geometric structure of modifier chains determined by the adsorption method. The geometric structure was also evaluated by atomic force microscopy (AFM), and we could obtain the hexagonal packing of chains of the modifiers both in water and air at high surface modification ratio. Imaging of the surface of the nanosized particles on a glass plate was accomplished in water by taking advantage of the hydrophobic attractive force, which was proved by adhesion force measurements.