An experimental investigation was conducted to observe bubble separation and collision phenomena during subcooled boiling of water on heating wires, and a theoretical model was proposed to describe the associated dynamical phenomena and understand the physical significance. Both experimental and theoretical evidences indicate that interfacial thermocapillary force induced by temperature difference and their interaction between neighbor bubbles was the most important forces during bubble separation and collision. The bubble separation process with positive effectual viscosity can be divided into two stages, accelerating and decelerating stage. The collision with an immobile bubble was concluded as an elastic collision, and the two equivalent bubbles just exchanged their momentum during their collision. Bubbles coalescence characteristics were also analyzed using the collision dynamics. The theoretical conclusions were compared with experimental results, showing a reasonable agreement with each other. (c) 2005 Elsevier Ltd. All rights reserved.