Introduction
H2 Chemistry is about understanding the concepts at the core and applying it to novel questions. There will be questions where concepts and knowledge memorised is applied directly (active recall), but it will be of a smaller proportion compared to O-level or IP exams. Common questions types for each topic will be similar though, and can be anticipated by finishing your tutorials and attempting past-year questions.
The length of the content is relatively manageable compared to other subjects, especially humanities subjects. You’ll be learning the vast majority of inorganic chemistry (e.g. Atomic Structure, Ideal Gas Law, Reaction Kinetics, Chemical Equilibria) in JC1 plus the first few chapters of Organic Chemistry (e.g. Introduction, Stereochemistry, Alkanes, Alkenes), while the remainder is covered in JC2.
Differences from Secondary School
In H2 Chemistry, you delve deeper into the subject in these two ways:
Firstly, you find out that some of the concepts you learnt in secondary school are actually “lies”, and will be replaced with more accurate theories (only to have them somewhat subverted in university Chemistry if you go that far). For instance, the planetary model of the atom where electrons revolve around the nucleus is replaced with spdf orbitals.
Secondly, H2 Chemistry goes into greater detail. One big area where this occurs is in Organic Chemistry. Apart from learning about the reactions of new functional groups / classes of organic compounds like benzene, amines and halogenoalkanes, you’ll also find out about some of their reaction mechanisms i.e. the step-by-step processes of how atoms and electrons “rearrange” themselves to form products, whereas they just magically change from reactants to products in secondary school. Furthermore, in Reaction Kinetics, while familiar concepts like activation energy, catalysts, and methods to change the rate of reaction do reappear in the JC syllabus, you’ll get more detailed analyses. For instance, in secondary school, you’re taught that increasing the concentration of a reactant can increase the rate of reaction, but the extent that the rate is changed is left ambiguous. Now in JC chemistry, you’ll learn about the concept of order of reaction and the rate equation, and find out that doubling the concentration of some reactants may double the rate (“first order”), while doubling that of others may result in a quadrupled rate (“second order”), still others having no effect on the rate at all (“zero order”).
Do expect a high degree of synoptic linking in questions that blend the different topics together, often between inorganic chemistry and organic chemistry. For instance, they may ask you to make mole calculations on organic compounds, or deduce the hybridisation of an atom in an organic compound etc.
While much of the questioning style is remarkably similar to O Level Chemistry (definitions, reaction conditions, explanations, balancing equations, drawing products, suggesting reasons etc), there are some new styles of questioning. An eminent example is structural elucidation for organic chemistry (I really dread such questions). These test your organic chemistry knowledge, inference and elimination skills, and can carry up to 10 marks. Basically, they give you a compound and describe many reactions that it goes through, or that the products of reactions with it go through, along with their observations. The question then asks you to identify, and usually draw out the mystery compounds, stating your reasons. While the high mark weightage might scare students, fret not. There's a set format that you can follow that still earns you “method marks”, so do find out from your teachers. Note that these questions don't always come out though.
H2 Chemistry also requires a bit more mathematical calculations than in secondary school. You’ll still be expected to make stoichiometric calculations, but on top of that H2 Chemistry also now quantifies previously qualitative concepts about acidity / basicity, electrochemistry, and thermochemistry. However, rest assured that the math doesn’t get too complex; there’s no differentiation, integration or even quadratic equations.
Examination Structure
There’s four papers you take in H2 Chemistry: Paper 1, 2, 3, 4. Paper 1 is 30 MCQ questions in an hour, hence 2 minutes per mark roughly (however, some time for shading is needed). Paper 2 is Structured and Data-based Question to be completed in 2 hours. Paper 3 includes Free Response Questions where you can choose which 2 questions out of 3. Paper 4 is a 2 hour 30 minute practical paper.
Paper 1: MCQ
This is usually the one of the most time-tight papers because there are 30 questions but only 1 hour. In other words, the average time spent per question cannot exceed 2 minutes. While this sounds daunting, there usually are questions that take less than 30 seconds to answer that can buy you more time on the more challenging ones, and you’ll get better with practice! Employing techniques like elimination can help you accelerate your answering process. There will be some easy and difficult questions, especially for the actual A levels. It is important to do the easy questions quickly to bank some time up for the difficult questions!
Common Mistakes in MCQ:
Careless mistakes - e.g. seeing a similar question to on that you have attempted before and rushing to answer it quickly, without paying attention to what may have changed
Unclear concepts and lack of memorization of definitions (e.g. poor understanding of the definitions in Energetics)
Paper 2 and 3: Structured and Data-based Question; Free Response Question
Paper 2 and 3 questions share quite a lot of similarities in that they’re both open-ended and the skills demanded are very similar. There are however some differences.
All Paper 2 questions are compulsory, but it does carry a slightly lower weightage compared to Paper 3. Do expect some data-based questions to come out. These provide you with sets of data for you to interpret, apply the chemistry concepts you’ve learnt and make some inferences, sometimes beyond the syllabus. There are some instances when one set of data isn’t actually relevant to the question and is just there as a distraction, though this is rare.
Paper 3 is composed of Section A and Section B. Section A questions are all compulsory, but Section B contains two 25 mark questions for you to choose one to do. For the choosing of the questions in Section B, questions will be of similar difficulty. You could go by eliminating the question with whichever topic you are least familiar with. If it's about the same, then have a quick glance through. Normally one question would be more active recall based while one would be the most application based. You could decide based on that. Don't spend too much time deciding!
Across both papers, do expect some out-of-syllabus concepts or reaction mechanisms to be introduced to you briefly in your paper before being asked to apply them (this has happened before in the recent A level papers).
Paper 4: Practical
Do expect some questions on theoretical chemistry concepts to come out even though it is a practical paper. It is therefore best for students to study your non-practical chemistry before the paper as well. In the A level paper you will likely be tasked to do several separate experiments covering different skills like mole calculation, titration and organic / inorganic Qualitative Analysis, as well as a planning component where you are tasked to plan out an experiment. Sometimes, you may be asked to carry out that planned experiment though this doesn’t always happen. You’re expected to be very detailed about the step-by-step process, and there are some standard steps you can memorise for procedures such as preparing a standard solution, titration, conducting QA and organic synthesis (the creation of a desired organic compound). Hence, do not underestimate the practical, as it does require you to set aside some time to study for it in order to score.
Paper 4 might be the paper with the toughest time management for many, especially for those fixated on perfection. For paper 4, I would imagine that there are 2 main types of weaknesses:
(1) Not having the theory knowledge for paper 4
There will be quite a lot of content to memorise for the practical planning question, so do study for it.
You must also understand the theory behind your experiments. So do not just blindly follow instructions without knowing what is going on. If you struggle with the aforementioned issue, get the practise in during your school practical lessons. Don't copy your friends’ actions; do your own carefully!
(2) Being clumsy and careless in doing the physical experiments due to lack of practice / familiarization with being in the lab
Make sure you pay attention during practical lessons, because it is the one most difficult to play catch-up on. A lot of students just end up following what others around them are doing, but this is not helpful in the long run because they are unfamiliar with the fundamental procedures needed for the experiments (e.g. pipette and burette washing, experimental techniques) since they rely on others’ actions to jog their memory. During exams, you can’t be looking around at others to be reminded of the steps needed.
That being said, while you shouldn’t be hasty in doing your experiments, don't be fixated on perfection as well! Move on if you are stuck, because there will always be questions that are much harder to score than others. It’s important to maximise your time for chemistry practicals to gain the most marks.
General Exam Tips and Common Mistakes
Make your revision as frequent and consistent as possible - consistency is extremely important in chemistry, more so than other subjects in my opinion.
Do not underestimate the type of reaction, definitions and reaction conditions (for organic chemistry + Haber process). Memorise them by heart and do not miss out keywords, because these do come out in exams and carry precious, brainless marks. There will be quite a lot of definitions especially for Energetics and Kinetics.
Be very careful about units in your calculation because that’s where students usually lose marks. (e.g. Ideal Gas Law: not converting temperature to Kelvin, not converting volume of gas to m3; Electrochemical: forgetting to convert delta G into J/mol instead of kJ/mol etc.)
For organic chemistry:
Be very conscious of the reaction conditions (temperature, acid or base, pressure etc.) and other functional groups apart from the one in focus when the organic compound has multiple groups. If conditions are right, other functional groups may also be changed so your answers should reflect that (e.g. KMnO4 in H2SO4 not only causes oxidative cleavage, but the acid can also cause acid hydrolysis, which a lot of people forget).
If conditions are basic, your acidic and basic groups should be deprotonated (e.g. -COO-, -NH2). If conditions are acidic, they should be protonated! (-COOH, -NH3+)
Be very cautious about the nuances and changes in reaction conditions. E.g. aliphatic alcohols are very weak acids so they only react with Na metal and won’t be deprotonated in the presence of NaOH, whereas phenol reacts with both.
When asked to draw the displayed formula / full structural formula in exams, please, please draw out all your bonds! (except for benzene rings, which can be left as rings). Students often forget to draw -O-H and leave it as -OH.
When asked to draw the structural formula of something, check your drawing to ensure you have the correct number of carbon atoms (especially for skeletal formulae) and placement of functional groups.
Don’t panic when they give you out-of-syllabus functional groups. Some are often analogous / similar to groups you already know (E.g. -SH and -OH etc). They may have similar chemical properties / go through similar reactions with similar reaction mechanisms to those you already know.
Also, don’t panic if they give you out-of-syllabus reactions / mechanisms too. Usually these questions will give you an example, and then give you another reactant to infer the product, or the reverse. These typically involve simple pattern recognition. Just follow the pattern and you've done most of the work already.
To determine how long and how many concepts you should cover your open-ended answers, look at the number of marks given.
Schools often give revision packages for your internal common tests/block tests, promotional examinations and prelim exams. Practice is key so do make good use of them! These packages are typically compilations of other school questions. As you know, block tests, promos and prelims will be more difficult than the final A levels, and grading will be much harsher. Don't be discouraged and don't let that stop you from clarifying all your misunderstandings with teachers and friends!
Contributed by:
Ho Song Yee (HCI’20)
A for Chemistry in 2020 A levels
High Distinction for Chemistry under the Hwa Chong Diploma
Anonymous (HCI’20)
HCI GATE Chemistry and H3 Chemistry
A for Chemistry and Distinction for H3 Chemistry in 2020 A levels
High Distinction for Chemistry under the Hwa Chong Diploma
Edited by Judith Ko