In pairs or small groups students develop key questions on the concepts being studied and record them on the postcard in the Postcard Problem section. Questions should be open-ended and complex. They record an expected answer on another piece of paper or in their books. Postcards are then ‘mailed’ to another pair or group who discuss the problem posed and then record an answer to the problem with an explanation or justification. The postcards are collected again and delivered to another pair or group for an alternative response. This can be repeated a number of times and then the postcards are returned to the senders. The senders consider the responses, compare them to their original response and then share/record their reflections.