This study was designed to investigate the strategies used by teachers and students for solving problems of varying familiarity in electrochemistry. Ten teachers and thirty-three of their upper secondary school students (Grade 12, ages 16 to 18) were asked individually to think aloud while they were solving three problems. The protocols (transcripts of the oral and written solutions) were analysed to identify their problem solving strategies. A two-phase general strategy of problem solving that encompasses the various approaches used by both the teachers and the students was identified. This consisted of seven significant processes.