When two small bubbles approach each other, a dimpled thin liquid film is formed between them. A model is developed for the dynamics of the thinning film with mobile interfaces, in which the effects of mass transfer and physical properties upon the drainage and rupture of the dimpled liquid film are investigated. The model predicts the coalescence time, which is the time required for the thinning and rupture of the liquid film, given only the radii of the bubbles and the required physical properties of the liquid and the surface, such as surface tension, London-van der Waals constants, bulk and surface diffusion coefficients. The predicted result is in good agreement with previous experimental results.