If you’re applying to study Natural Sciences at Cambridge, you should be ready for a range of questions covering Chemistry, as well as others covering the range of Sciences. You should have a framework ready to answer questions, especially those that are more difficult, or that stray further from the typical syllabus.
Initially, you should work to put the question into context. What area does it fall in? Through considering it further and working to place it within a framework that you understand, you’ll be better able to answer it.
Next, apply your A Level knowledge. That means deploying as much relevant knowledge as you can, and using it as the basis for your answer. Of course, this knowledge might not make much of a dent in the question – but it should lay the foundations.
After this, you ought to bring in your extra knowledge. That means outside reading, experiments you’ve done, your EPQ, other projects, etc. Try to use this to set yourself apart from other students.
Lastly, try to build out an answer that develops on the above knowledge, and uses prompts and information supplied by the tutor that you’re talking to as well. The key here is to develop a rapport with the tutor, and show that you’re the kind of student that they can teach. Show a willingness to take on new ideas and develop them.