In this paper, we present an emotion and memory model for a social robot. The model allowed the robot to create a memory account of a child's emotional events over 4 individual sessions. The robot then adapted its behaviour based on the developed memory. We tested our model through using the NAO robot. The robot was programmed to teach vocabulary to children during the popular game 'Snakes and Ladders'. We conducted a between-subject study with 24 children at a primary school to check the validity of our model. We also evaluated the impact of robot's positive, negative, and neutral emotional feedback of the NAO robot on children vocabulary learning. Three groups of children (8/group) interacted with the robot for four different times during three weeks. Our results showed that the condition where the robot displayed positive emotional responses had a significant effect on the child's learning performance as compared to the two other conditions: negative feedback and neutral feedback. In addition, our model helped children in improving their vocabulary.