2020/21 Update: Registration for the 2021 Cambridge Chemistry Challenge which is due to take place in June or July 2021 will start in early 2021.
After five successful years of online challenges, there are 180 puzzles that are available to students and teachers. The entry level question for one of the challenges, chosen at random, is shown above. The other challenges can be found by clicking "The Online Challenge" panel below. We hope you have enjoyed the challenges as they came out, however, there are no plans to release new puzzles.