Chemistry

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Lectures

Chemistry is a very popular choice with both biological and physical Natural Science students. First year covers physical, organic, and inorganic chemistry, setting the foundation for second year if you decide to pursue either organic or physical (or both). The majority of the notes are present in the lecture booklets and the annotations missing are filled in during the lecture. Skimming the notes ahead of a lecture is good preparation and try to make sure you understand the previous lecture before the next one otherwise it is easy to become quickly confused. Lecturers are happy to answer questions at the end of the lecture. There are 3 chemistry lectures a week.

The lecture series titles and a brief description of each are listed below:

Michaelmas:
  • The Shapes and Structures of Molecules Part 1: Covers the analysis of molecules and their structures using methods of proton NMR, carbon NMR and infrared spectroscopy.
  • The Shapes and Structures of Molecules Part 2: Covers the atomic and molecular orbitals to molecular shape and interactions between them. Diagrams are a good way to explain these concepts in the exam.
  • Reactions and Mechanisms in Organic Chemistry Part 1: Covers examples of reaction mechanisms and the theory behind why and how these happen.
Lent:
  • Reactions and Mechanisms in Organic Chemistry Part 2: Covers more complex reaction mechanisms. It is often possible to work out mechanism steps from the theory taught in lectures and get good marks but it’s also a good idea to rote learn the mechanisms given in the examples and the notes for the exam.
  • Energetics and Equilibria: Covers spontaneous and nonspontaneous reactions and majors on the second law of thermodynamics. There are several equations and derivations to learn so making a list as you go through the lectures is a good approach.
  • Kinetics of Chemical Reactions: Covers reaction kinetics and after doing the supervision questions the methods should be relatively straightforward to apply to exam questions.
Easter:
  • Chemistry of Elements: Covers several examples of a few concepts (e.g. Zeff, d/f-block contraction, relativistic effects) and is a very qualitative approach. When answering questions for supervisions, the structure of your answers is important; try to give a definition (eg. of bond energies), diagram or graph (eg. of hard/soft bonds), main trend/reason for the trend, anomalies/reason for anomalies. Try not to write long answers as you won’t have time in the exam for it – diagrams are usually the best way to condense as much information into your answers quickly.

Supervisions

At the back of the lecture booklets, there are several questions. Each week your supervisor is likely to set around 10-20 questions. Answer these as well as you can as many of them are very similar to exam questions so it’s very good practice. The supervisions will most likely be based on going through the corrections to these questions. The answers to these questions are often not released so make sure you understand your supervisor’s comments.

Practicals

There is one chemistry practical every other week. Reading up on the practical before is a good way to speed up completing the practical on the day. The practicals are marked with a descriptor- distinction, merit, pass or fail. It is rare for students to be given a distinction, and even merits are not typical so don’t be discouraged by a pass! The marking for the chemistry practicals tends to be quite subjective despite being moderated. Don’t worry too much about this as the practicals contribute only 20% to your final mark, instead focus on building your skills in the lab. Ask your demonstrator if you aren’t sure about anything or if you don’t know why the method requires certain steps. Getting a pass mark for each practical should be pretty straightforward (remember to sign the risk assessment or you will lose all marks for that practical!).

Almost all the practicals must be written up and handed in on the day although there is one longer practical which can be written up over Christmas. ChemDraw (see ‘Useful Resources’) is a very useful resource for interpreting spectra of the compounds in the write-ups.

Practicals for the academic year 2020-21 are cancelled for Chemistry IA, which will be replaced by a series of exercises based on experimental work. For further detail, visit https://www.ch.cam.ac.uk/teaching/.

Revision

Past papers are the best practice for the chemistry exam. Model answers are available on Moodle, though the answers are not perfect and contain some mistakes. Remember there may be more than one possible answer for a question so don’t be discouraged if your answers are different. Practice doing timed papers close to the exam. Clayden’s Organic Chemistry textbook has practice questions at the end of chapters which may be useful for the Reactions and Mechanisms course. There is also a solutions manual available – try the library.

Exams

There is one exam at the end which is 3 hours long, counting for 80% of your final mark. There are 6 questions- one from each course. Make sure you manage your time carefully in the exam as there is strong time pressure. Answer questions you are most comfortable with first to build confidence. Set a time limit for questions (around 25 minutes) and move onto the next question when your time is up. At the end, you can always come back to questions you’ve left. Often giving incomplete answers can grab you a reasonable number of marks. This is particularly true for the Reactions and Mechanisms course, where even if your answer is wrong, you may pick up marks for showing knowledge of the mechanisms/importance of pKa values etc.

Useful resources

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