Ah, QCE Chemistry exams - a delightful mix of equations, definitions, and a healthy dose of panic. But fear not! If you’ve ever left an exam muttering, “I definitely failed that,” only to be pleasantly surprised, you’re not alone. However, to truly ace your chemistry exam, you need to dodge some classic mistakes. Let’s break them down (just like a decomposition reaction - yes, I went there).
1. Mishandling Significant Figures
Chemistry teachers are obsessed with significant figures, and for good reason. If the question specifies a certain number of sig figs and you ignore it, kiss those marks goodbye.
How to avoid it:
- Always check how many significant figures are in the data given.
- If the question says “correct to three significant figures,” don’t suddenly decide that four looks prettier.
- When in doubt, follow the least number of sig figs in the given data (unless it’s a multi-step calculation—then use more and round at the end).
🚨 Example fail:
- Correct answer: 12.4 g (3 significant figures)
- Your answer: 12.37691 g (overly enthusiastic)
- Teacher’s response: "Nice try, but nope."
2. Forgetting State Symbols in Equations
You might think, “Do I really need to write (s), (l), (g), or (aq)?” Yes. Yes, you do. Those tiny letters can make the difference between a balanced equation and a deduction of marks.
How to avoid it:
- Memorise your common state symbols.
- If you're dealing with an acid-base reaction in water, assume everything is aqueous unless told otherwise.
- Gases (like H₂ and CO₂) are (g), solids (like precipitates) are (s), and water is always (l).
💡 Case Study: In a past QCE exam, students who forgot state symbols in a precipitation reaction lost an easy two marks. Don’t be that student.
3. Not Showing Full Working in Calculations
Even if you miraculously arrive at the correct answer, if you don’t show your steps, your teacher will assume you consulted some divine chemistry spirit rather than actually knowing what you’re doing.
How to avoid it:
- Always include formulae before plugging in numbers.
- Use units at every step.
- Box or highlight your final answer so it doesn’t get lost in a sea of scribbles.
🚨 Example fail:
- Question: Calculate the number of moles in 25g of NaCl.
- Your response: 0.427 (no working shown)
- Teacher’s feedback: "I am not a mind reader. Show your steps."
4. Messing Up Acid-Base and Redox Reactions
Half-equations and balancing reactions can be a nightmare if you don’t practise. One wrong coefficient, and suddenly water is breaking the laws of chemistry.
How to avoid it:
- Use the OIL RIG method for redox reactions (Oxidation Is Loss, Reduction Is Gain of electrons).
- Practise writing half-equations—seriously, do at least 10 before the exam.
- If dealing with acidic conditions, remember to balance oxygens with H₂O and hydrogens with H⁺.
💡 Tip: Think of oxidation as a fire (burning gives off oxygen), and reduction as rescue (gaining electrons like a life-saving recharge!).
5. Misreading the Question (a.k.a. The Silent Killer of Marks)
So, you speed-read a question and think, “Easy! I got this.” Five minutes later, you realise you answered something completely different. Oops.
How to avoid it:
- Underline or highlight key terms (e.g., explain, justify, calculate, describe).
- If it’s a multi-part question, make sure you address all parts.
- Don’t assume—read twice before answering.
🚨 Example fail:
- Question: Explain why HCl is a strong acid.
- Your response: "Because it burns skin."
- Correct response: "HCl fully ionises in aqueous solution, meaning it donates all its protons, leading to a high concentration of H⁺ ions."
6. Poor Time Management
Leaving a 5-mark extended response until the last 2 minutes of the exam? Bold strategy. Doesn’t usually pay off.
How to avoid it:
- Allocate time per question based on marks. A 10-mark question? Spend at least 10–12 minutes on it.
- If you get stuck, move on and come back later.
- Keep an eye on the clock—don’t get lost in a single question.
7. Neglecting Past Papers
If you’re not doing past exams, you’re basically trying to learn to swim by reading about it. It won’t end well.
How to avoid it:
- Do as many QCE past papers as possible.
- Time yourself under exam conditions.
- Analyse marking schemes to see what examiners expect.
💡 Case Study: Students who practised at least five past exams scored, on average, 15% higher than those who didn’t. Let that sink in.
Final Thoughts
Chemistry is tough—but so are you. By avoiding these common mistakes, you’ll be setting yourself up for top marks. Practise consistently, revise smartly, and remember: chemistry is just like baking, but with more explosions (and fewer edible results). You’ve got this. Now go smash that exam!
If you found these tips helpful, I’d personally love to support you as your tutor this year. You can view my profile here on Learnmate and contact me to discuss tutoring.
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