Abstarct: The impact of solid particles has a wide application in yhe industry and has recently been the subject of many scientific studies. One of the most important applications of this topic is in the mineral industry. Film flotation is a process for separating hydrophobic mineral materials from hydrophilic. In this study, for simulation of this process, the impact of spherical hydrophobic particles on an air–liquid interface was experimented. The aim is to obtain a critical impact velocity in which the hydrophobic particle remains on the liquid surface so that it penetrates completely at higher velocities than the critical velocity. A mathematical model was developed baxsed on energy balance to predict the critical velocity. The Teflon particles of diameter 3-5mm were used. Distilled water and boger fluid were used as the fluids in experiments. Particle fall into the fluid were captured by using a high speed video camera with the rate of 4500 fps. . For Teflon spherical hydrophobic particles two floatation and penetration regimes were observed from experiments. After processing of sequential images, the motion of a particle inside the fluid was obtained and for the first time, the maximum penetration depth, rebound depth, rebound height and the pinch off depth were determined for each particle and It was found that, at critical velocities and near them, particle penetration is associated with oscillations, and at higher velocities than the critical, the number of oscillations decreases, so that the particle gets separated from the liquid surface without any oscillations. The Dependence of maximum penetration depth on drop height was studied and it was found that with increasing drop height, the maximum penetration depth also increases. Also, the effect of particle size on critical velocity was investigated and it was observed that with increasing particle size the critical velocity decreases. In addition, the particle velocity and the velocity of the three-phase contact line were plotted at critical conditions. The developed mathematical model was compared with the experimental observations, and it was found that in the modeling range, there is good agreement with the values of the obtained data.