Every year, A-level Chemistry examiners report the same mistakes by students:

  • Vague explanations
  • Misused terminology
  • Missing key details
  • Answers that don’t quite answer the question

And here’s the frustrating part:

Most of these mistakes happen even when students understand the topic.

This article—which takes a tour of the 7 biggest mistakes that are costing A-level Chemistry students serious marks—is your shortcut to avoiding those traps, so you can shoot for that A*.

(You can find even more exam guides like this one in Brainscape’s free A-level Academy.)

Let’s dive in.

A-level Chemistry Mistake # 1: Underestimating Content Knowledge

“I’ve got the formula sheet, calculator, and periodic table, I’ll be fine.” Sound familiar?

It’s true that A-level Chemistry gives you tools and that, with the right methodology, you can execute the calculations and marks.

But those tools don’t replace content knowledge.

You still need to:

  • Recognise which concepts apply
  • Understand what the question is really asking
  • Recall key definitions and relationships quickly

Without that foundation, even simple questions become slow and uncertain.

The Fix

Build strong, automatic recall of core concepts. And the best tool for the job is a digital flashcard app like Brainscape, which has distilled each A-level Chemistry board syllabus into a structured collection of flashcards (click on the board that’s relevant to you):

The app then delivers these concepts to you via a spaced repetition algorithm that’s designed to help you learn as efficiently and painlessly as possible, transforming the words in your chemistry textbook into long-term memory. 

(We also have a library of flashcards for dozens of other A-level subjects and boards: look for the ones with the little green ticks).

By studying these flashcards a little bit every day, you can:

  • Lock in key definitions and distinctions
  • Reinforce high-frequency concepts
  • Make fast, efficient progress on banking essential content knowledge

Brainscape’s A-level Chemistry flashcards also come with three free practice test papers, which have been written to mimic the content and difficulty of a real A-level Chemistry exam.

These will give you an excellent opportunity to:

  • Identify your knowledge weaknesses
  • Work on your pacing (timing)
  • Practice your test-taking skills 

Read: The 20 Best Test-Taking Strategies Used By Top Students

A-level Chemistry Mistake # 2: Giving Vague Answers In Explanations

This is one of the most common (and costly) mistakes.

For example: “Explain why increasing the temperature increases the rate of a reaction.”

Bad answer: “There are more collisions.”

That’s extremely vague. 

The Fix

A stronger answer would be: “There are more successful collisions with energy greater than the activation energy.”

Examiners are looking for an explanation, not a statement. (“There is X and so Y”). In this context, there aren’t just more collisions but specifically successful collisions.

  • Collisions with enough energy
  • Collisions that overcome activation energy

If you want to sharpen this skill further, check out our guide on How To Decode A-Level Chemistry Command Words.

A-level Chemistry Mistake # 3: Confusing Key Terms

Certain pairs of concepts trip students up again and again.

Intermolecular Forces vs Bonds

Mistake: Talking about breaking covalent bonds when discussing boiling

In reality:

  • Intermolecular forces are broken during boiling
  • Covalent bonds remain intact

Oxidation vs Reduction

Mistake: Mixing up the loss and gain of electrons

Quick reminder:

  • Oxidation = loss of electrons
  • Reduction = gain of electrons

The Fix

In order to correct common confusions and misconceptions like this, you need to be able to define them precisely and apply them in context.

Practicing your content knowledge with flashcards are particularly powerful here because they compel you to develop clear mental distinctions, instead of relying on vague familiarity.

A-level Chemistry Mistake # 4: Writing Generic Equilibrium Answers

Equilibrium questions are another classic trap. For example:

Question: The following equilibrium is established in a closed system:N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH = –92 kJ mol⁻¹

Explain how increasing the temperature affects the position of equilibrium.

The mistake would be writing: “The equilibrium shifts to oppose the change.”

Sure, that’s true, but incomplete. The examiners are looking for a direction linked to the specific change.

The Fix

Always include the direction (left or right) and the reasoning.

For example: “The equilibrium shifts to the right to oppose the increase in temperature, favouring the endothermic reaction.”

A-level Chemistry Mistake # 5: Are You Forgetting State Symbols In Equations?

This is one of the easiest marks to miss. It’s forgetting to specify the state in your equations.

For example, it’s writing: CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O

Instead of: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)

  • (s) solid → calcium carbonate (marble chips)
  • (aq) aqueous → hydrochloric acid and calcium chloride (dissolved in water)
  • (g) gas → carbon dioxide (you’d see bubbling)
  • (l) liquid → water

State symbols matter because they show physical state, reaction conditions, and whether species are dissolved.

The Fix

Make it a habit. For every equation, include state symbols. No exceptions.

A-level Chemistry Mistake # 6: Not Providing Sufficient Information to Satisfy Mark Allocation

Students often write what feels like a complete explanation, only to pick up 1 or 2 marks out of 4 or 6.

Why?

Because A-level Chemistry marking is often based on one clear, creditworthy point per mark. So if a question is worth 4 marks, the examiner is usually looking for four distinct ideas.

Sample question: “Explain why increasing the temperature increases the rate of reaction. (4 marks)”

A typical underdeveloped answer would be: “Particles have more energy and move faster, so the rate increases.”

This might earn 1–2 marks.

The Fix

Provide enough detail to satisfy the mark allocation.

For example: “Particles have more kinetic energy, so they move faster and collide more frequently. A greater proportion of collisions have energy greater than the activation energy, resulting in more successful collisions per second, so the rate of reaction increases.”

Now you’ve covered:

  • Increased kinetic energy
  • Increased collision frequency
  • Reference to activation energy
  • Successful collisions
  • Link to rate

That’s multiple distinct, markable points.

So, before you start writing, ask yourself: “How many marks is this worth?”

Then aim to include at least one clear point per mark and develop your explanation step by step.

If you want more practice structuring longer answers like this, check out our guide ‘How To Answer Extended Response Questions In A-Level Chemistry’.

A-level Chemistry Mistake # 7: Losing Marks On Calculations

Calculation errors often come down to missing units, incorrect significant figures, and skipped steps.

Even strong students lose marks here through carelessness. 

The Fix

Make sure you:

  • Include your units
  • Use the right ones depending on the formula you’re working with
  • Avoid rounding up or down until right at the end
  • Show ALL of your working

If this is a weak spot, read: ‘How To Avoid Losing Marks On A-Level Chemistry Calculation Questions’.

Final Thoughts: Small Mistakes, Big Impact In A-Level Chemistry

The difference between a B an A* A-level Chemistry paper is precision, clarity, and attention to detail. The difference between grades often comes down to:

  • One missing phrase
  • One incorrect unit of measurement
  • One vague explanation

The good news?

These are all fixable!

And once you start spotting these patterns, you’ll avoid mistakes and start picking up marks that many students leave behind.