Cambridge Chemistry Challenge (C3L6)
A UK chemistry competition where students solve challenging written problems that extend beyond the standard school syllabus. Open to students in Year 12 or below through participating UK schools. Rated Advanced Level, with difficulty mainly coming from unfamiliar contexts, multi-step chemical reasoning and university-style problem-solving.
Verified information
Competition details can change. Always confirm dates, eligibility and entry requirements on the official organiser's website.
Official website ↗OVERALL COMPETITION LEVEL
Advanced Level
4 evaluation dimensions have source-backed automatic scores; 0 dimensions need conflict review.
Competition overview
Key information
Eligible ages
12–17
School level
Lower Sixth / Year 12 focus
Registration method
School Only
Competition stages
School registration, competition window, teacher marks submission, moderation, results
Fee
Not yet announced by the organiser
Online / in-person
Hybrid
Dates
Competition timeline
Registration opens
1 Sept 2025
Registration closes
29 May 2026
Competition starts
2 Jun 2026
Competition ends
18 Jun 2026
Editorial perspective
Our Take
The Cambridge Chemistry Challenge, usually known as C3L6, is a Lower Sixth chemistry competition associated with the University of Cambridge’s chemistry outreach. It is supported by St Catharine’s College, the Cambridge Department of Chemistry, Oxford University Press and the Michael and Morven Heller Charitable Foundation. The programme was developed as an outreach activity to show that chemistry can be interesting, difficult and relevant, rather than reducing the subject to routine school assessments. The competition is aimed mainly at Year 12 students and is designed by experienced teachers and university chemists. Its 90-minute paper deliberately reaches beyond the standard syllabus, but it remains accessible enough to introduce students to university-style chemical thinking. The best questions are not necessarily the ones requiring the most advanced facts. They ask students to connect structure, reactivity, data and quantitative ideas, then decide how to make a convincing argument from limited information. C3L6 has a distinctive enrichment outcome as well as a competition result. Strong performers can receive certificates and, at the highest level, invitations to a residential Cambridge chemistry experience. The competition is also a useful preparation point before the later-year UK Chemistry Olympiad, but it should not be presented as a formal qualifying round for that competition. The relationship is educational and developmental: C3L6 helps students build the habit of tackling unfamiliar chemistry before they face the more advanced RSC Olympiad paper. We rate the Cambridge Chemistry Challenge at Advanced Level. The school-based entry route is relatively accessible, but the unfamiliar contexts, time pressure and beyond-syllabus reasoning make it substantially more demanding than ordinary Year 12 exercises. It is a strong fit for students considering chemistry, medicine, natural sciences, chemical engineering or materials science, especially those who want to test whether they enjoy thinking like a chemist rather than simply achieving high classroom marks.
Read full guide →Preparation support
Recommended resources
C3L6 Downloads
Open resource ↗Official archive of papers, answer booklets, mark schemes and competition reports.
Official · Free · Past-paper and solution archive · Essential
C3L6 Online Challenges
Open resource ↗Large official bank of short chemistry puzzles for frequent practice.
Official · Free · Interactive practice system · Essential
C3L6 2024 Question Paper
Open resource ↗Recent 90-minute paper showing the scaffolded, beyond-syllabus question style.
Official · Free · Past paper · Recommended
C3L6 2023 Teacher Mark Scheme
Open resource ↗Detailed marking showing expected calculations, structures, reasoning and partial credit.
Official · Free · Mark scheme and worked answers · Recommended