This paper presents a unified and simple quasi-steady-state model that can be used to describe a number of important applications. The model can be applied to all moving boundary problems whenever sensible heat can be ignored. Some of the experimental measurements available in the literature on frying of thin and thick potato chips, freeze drying of meat, solidification of waxes and air drying of potato chips were used to test the validity of the model. The agreement between the model predictions and the experiments was reasonably good; especially it has been done for a wide range of applications. The model, which was analytical one, was developed further to generate a unified dimensionless equation that can be used to predict the extent and rate of drying and frying. The generalised equation is expected to describe the heat and mass transfer in some other applications, which has not been considered in this paper.