Hardest A Level Chemistry Topics & How To Tackle Them

Students often say A Level Chemistry is hard, and it’s hard because there are topics that feel like they belong to a completely different subject, especially in comparison to GCSE Chemistry.  

Every student who has ever sat in front of a tricky mechanisms question or stared blankly at an NMR spectrum has felt exactly the same way. You're not alone! 

With your A Level Chemistry exams approaching, now is the time to face the hardest topics directly.

As a teacher, I've spent years supporting students with their A Level Chemistry exams, and the same topics come up again and again as the ones that cause the most difficulty.

In this article, I'll walk you through exactly what those topics are, why they're hard, and what you can do about it.

Key Takeaways

• Organic mechanisms, equilibrium and Kc calculations, electrochemistry, spectroscopy and structure determination, and thermodynamics are consistently the A Level Chemistry topics students find hardest across regardless of whether they are taking AQA, Edexcel and OCR.

• A Level Chemistry is challenging because it combines three almost separate disciplines - physical, organic and inorganic chemistry - all in one course, and demands high level mathematical, analytical and conceptual skills at the same time.

• The most effective revision strategies involve building strong foundations first, practising applying knowledge to unfamiliar contexts, and using past papers strategically.

Why A Level Chemistry Is Challenging

A Level Chemistry is a big step up from GCSE. Here’s why students find it challenging:

Three subjects in one.

A Level Chemistry splits into three distinct areas: physical chemistry, organic chemistry and inorganic chemistry.

Each of the three areas of Chemistry feels almost like a separate subject, and you need to master all of them. 

The maths feels more demanding.

Just like at GCSE, 20% of marks in your A Level exams must come from maths-based questions that are at least as difficult as a Higher Tier GCSE.

You need confident skills in algebra and handling logarithms, and you need to use scientific notation effortlessly on your calculator. For some students, the amount of maths in A Level Chemistry is the hardest thing to get to grips with.

You need to apply, not just recall.

The hardest A Level Chemistry questions are less about simple recall and more about application and analysis. They require applying knowledge to unfamiliar situations. You can know every fact on the specification and still struggle with an exam question that presents a scenario you've never seen before.

There is a lot of content to learn!

A Level Chemistry covers an enormous range of topics across two years. Topics connect to each other in ways that aren't always obvious, and exam questions regularly expect you to draw on several areas at once.

The Hardest A Level Chemistry Topics

When I'm running A Level Chemistry revision sessions, the same topics get requested again and again. Here are the five that consistently cause the most difficulty:

1. Organic Mechanisms

Organic mechanisms are the topic I hear about most from my students. 

At GCSE, organic chemistry asks you to recall reactions. At A Level, it asks you to understand and draw the movement of electrons through a molecule using curly arrows. That is a fundamentally different skill.

The hardest part is knowing exactly what is attracted to what, which electrons move where, and where to draw the arrows.

Confusing nucleophiles and electrophiles is one of the most common mistakes.A nucleophile donates an electron pair. An electrophile accepts one. Always think about electron flow rather than memorising definitions.

There are also a lot of different mechanism types to learn: nucleophilic substitution, electrophilic addition, electrophilic substitution, nucleophilic addition, and more. Each has its own rules, conditions and curly arrow conventions. Getting one arrow wrong can cost you marks even if the rest of the answer is correct.

The hardest questions require applying knowledge to unfamiliar situations. You might be shown a molecule you've never seen before and asked to draw a mechanism for it. That requires genuine understanding of how and why electrons move, not just memorisation.

Key reasons students struggle:

• Curly arrow notation is a completely new skill with no GCSE equivalent

• Nucleophiles and electrophiles are easy to confuse

• There are many different mechanism types, each with specific rules

• Exam questions often use unfamiliar molecules, requiring real understanding rather than recall

2. Equilibrium & Kc Calculations

You'll have met reversible reactions and Le Chatelier's Principle at GCSE. At A Level, equilibrium gets significantly more demanding.

The introduction of the equilibrium constant, Kc, adds a layer of mathematical complexity that many students find genuinely difficult.

Kc expressions require you to write equilibrium concentrations in the correct format, raise them to the correct powers, and then use them in multi-step calculations, all without making an error along the way.

The issue is less about the actual mathematics being difficult, and more about understanding why you are doing a particular calculation.

Students who learn the formula without understanding the concept behind it fall apart when questions are framed in unfamiliar ways.

The effect of temperature on Kc is another consistent source of confusion. Students know that temperature shifts the position of equilibrium, but at A Level you also need to understand what that means for the value of Kc itself.

The physical chemistry topics like acids, bases and buffers are full of complex calculations that can even be a problem for strong mathematicians. (opens in a new tab)Buffer calculations in particular combine equilibrium, acid chemistry and logarithms all in one question.

Key reasons students struggle:

• Writing Kc expressions correctly requires careful attention to stoichiometry

• Multi-step calculations leave many opportunities for small errors to compound

• The effect of changing conditions on Kc (as opposed to equilibrium position) is a common point of confusion

• Buffer and pH calculations combine multiple concepts at once

3. Electrochemistry

Electrochemistry builds on electrolysis from GCSE, but the A Level version is considerably more demanding.

At A Level, you need to understand standard electrode potentials, construct electrochemical cells, calculate cell EMF values, and use electrode potential data to predict whether reactions are feasible.

Each of these skills requires a solid understanding of REDOX chemistry, and that understanding needs to be very precise.

Explaining the chemical reasons for specific steps in analytical procedures involving redox reactions is something very few students can do well, illustrating how challenging it is.

It's not enough to know what happens. You need to explain why, at the level of electron transfer, in the correct direction, with the correct terminology.

Writing half equations and combining them into overall ionic equations is another area where marks get dropped consistently.

Students who are unsure of oxidation states, or who can't balance equations confidently, find electrochemistry questions very difficult to complete accurately.

Key reasons students struggle:

• Standard electrode potentials are a completely new concept with no GCSE equivalent

• REDOX half equations need to be written and balanced precisely

• Predicting feasibility from electrode potential data requires careful logical reasoning

• The topic draws heavily on oxidation states, which must be secure before this topic makes sense

4. Spectroscopy & Structure Determination

Spectroscopy questions ask you to look at data and work backwards to identify an unknown molecule. For many students, this feels very different to anything else in the course.

At A Level, you need to be able to interpret mass spectra, infrared spectra and NMR spectra, often in combination.

Spectroscopy combines data interpretation with chemical reasoning.

NMR needs understanding of splitting, chemical shift and integration. Students find it difficult because it demands several layers of thinking at once.

NMR is where most students find the biggest challenge.

You need to identify the number of different chemical environments, interpret splitting patterns using the n+1 rule, read chemical shift values, and integrate peak areas. Then, you have to use all of that information together to suggest a structure. That's a lot of simultaneous reasoning!

Most incorrect answers come from rushing, not from lack of ability. (opens in a new tab)Students who take a methodical, step by step approach to spectroscopy questions consistently outperform those who try to jump straight to an answer.

Key reasons students struggle:

• NMR requires several layers of reasoning to happen at the same time

• Splitting patterns are easy to misread, particularly for complex molecules

• Students often rush spectroscopy questions rather than working through them systematically

• IR, mass spectra and NMR all need to be interpreted together in the hardest questions

5. Thermodynamics — Entropy & Gibbs Free Energy

Thermodynamics is where A Level Chemistry gets abstract. 

You'll have encountered enthalpy at GCSE. Thermodynamics at A Level introduces entropy (ΔS) and Gibbs free energy (ΔG). It asks you to use all three together to determine whether a reaction is feasible, which is a significant leap in conceptual complexity.

Students struggle to visualise what a change in entropy looks like and how it affects feasibility. Free energy calculations bring together enthalpy, entropy and temperature in one expression, so the topic feels like a jump in complexity.  (opens in a new tab)

A particularly common mistake involves the effect of temperature on feasibility. If ΔH and ΔS have the same sign, temperature determines whether the reaction is feasible. Students who have memorised the formula without understanding it consistently get these questions wrong.

Understanding entropy conceptually is something students find especially hard.

The key is to connect entropy to something physical. Entropy increases when particles become more disordered, when solids become liquids or gases, or when one molecule becomes several.

Once you can visualise it, the calculations start to make more sense.

Key reasons students struggle:

• Entropy is abstract and hard to visualise

• The Gibbs free energy equation combines three separate variables in one expression

• The effect of temperature on feasibility requires careful logical reasoning when ΔH and ΔS have the same sign

• Students often confuse enthalpy and entropy changes, particularly in sign

Strategies for Mastering Difficult A Level Chemistry Topics

Understanding which topics are hard is just the first step. What matters most is how you revise them.

Here are the strategies I recommend to all my A Level Chemistry students.

Practise Past Papers Strategically

Past papers are your most powerful revision tool. But only if you use them properly.

I suggest two approaches. First, use past papers to target your weak spots. If spectroscopy questions always catch you out, pull every spectroscopy question from the past five years and work through them back to back. 

Reviewing and understanding your mistakes is the most important part of studying. Take time to analyse where you went wrong and why. This reflection is key to improving your problem-solving skills.

Second, practise under timed conditions. Get into the habit of completing full papers without your notes, in the time you'll have. Save My Exams' Mock Exams tool lets you do exactly that: full exam length papers in timed conditions, so exam day feels familiar rather than frightening.

Break Down Complex Problems

Multi-step problems - the kind that appear throughout physical chemistry and spectroscopy - are overwhelming when you look at them whole.

The secret to success: break them down!

Read the question carefully and identify exactly what you're being asked. Write down the information you've been given, and label it. Then work out which formula or approach links the two.

Write each step out separately. Don't try to do it in your head. This reduces errors, and means you can pick up method marks even if the final answer is wrong.

Save My Exams' revision notes include fully worked examples throughout. Use them actively. Cover up the solution, attempt the problem yourself, then check your reasoning step by step against the worked answer.

Master the Fundamentals First

The most common revision mistake at A Level is jumping straight to hard content when the foundations aren't solid.

Confidence is built through smart, consistent practice.  If you're struggling with Kc calculations, ask yourself: are you completely confident writing equilibrium expressions? If not, that's where to start. If electrochemistry feels impossible, check your understanding of oxidation states and REDOX first.

Almost everything in A Level Chemistry builds on something else. Mechanisms rely on understanding polarity and bond types.

Thermodynamics builds on enthalpy from AS. Electrochemistry requires REDOX to be secure.

Gaps in foundational knowledge make harder topics feel impossible, even when they're not.

This is where Save My Exams' Strengths and Weaknesses tool is so useful. It analyses your performance across topics and shows you exactly where your knowledge is strong and where the gaps are.

Rather than guessing where to spend your time, you get a clear, data-driven picture of what needs attention. Once you've found your weak spots, go back to the basics on those topics and read our revision notes to improve your understanding. 

Frequently Asked Questions

What is the pass rate for A Level Chemistry?

In 2025 (opens in a new tab), 32% of A Level Chemistry students achieved an A or A* grade, a very slight fall from 32.2% in 2024. The overall pass rate across all A Level subjects in 2025 was 97.4%.  (opens in a new tab)

Achieving the very top grades in A Level Chemistry is genuinely competitive. That makes it all the more important to focus your revision strategically, rather than spreading effort evenly across every topic.

How much harder is A Level Chemistry compared to GCSE?

A Level Chemistry is harder than GCSE. You’ll study familiar topics in greater depth, while also covering new organic chemistry areas and concepts like entropy and spectroscopy.

The biggest shift is from recall to application. At GCSE, you can do well by knowing facts and following procedures. At A Level, examiners regularly present you with unfamiliar scenarios and ask you to apply your understanding, which takes time and practice to develop.

How long should I spend revising for A Level Chemistry?

There's no single right answer, but a practical target for the months leading up to your exams is around three to four hours of focused Chemistry revision per week, increasing in the final few weeks.

Quality matters far more than quantity. An hour spent actively working through past paper questions or practising mechanisms is worth far more than three hours of passively rereading notes.

Do I need to revise all A Level Chemistry topics?

Yes, but you don't need to spend equal time on every topic.

Your exams will draw on content from across the whole specification, including synoptic questions that combine multiple topics. You can't afford to leave whole areas unrevised.

What you can do is be strategic. Use your past paper performance and Save My Exams' Strengths and Weaknesses tool to identify where your marks are being lost. Focus your deepest revision efforts there, and use past papers to make sure you're comfortable across the board.

Final Thoughts

Organic mechanisms, equilibrium, electrochemistry, spectroscopy and thermodynamics are hard. There's no point pretending otherwise. They ask you to think in new ways, apply knowledge to unfamiliar contexts and hold several ideas in your head at once.

But hard doesn't mean impossible. The students who do well in A Level Chemistry aren't necessarily the ones who find it easiest. They're the ones who understand where their weaknesses are, target them with the right strategies and keep practising consistently.

With the right approach, the right resources and a bit of persistence, you can master even the hardest A Level Chemistry topics and walk into your exam ready to show what you know.

References

• A Level Results 2025: Grades by Subject — Tes (opens in a new tab)