Most students don’t fail IGCSE Chemistry because they “don’t know Chemistry”. Marks are usually lost in predictable places: sloppy method, weak exam language, rushing calculations, and ignoring practical-style thinking. Fixing a small set of habits can change the outcome quickly.

1) Treating Chemistry like memorising notes

What happens: you can recall facts, yet you can’t apply them in unfamiliar questions.

Avoid it

• Swap passive reading for questions. After every topic, do 10–20 past-paper questions.
• Teach the idea out loud in 60 seconds. If you can’t, go back and rebuild the concept.

2) Not using mark-scheme language

What happens: your answer is “right” in your head, yet it doesn’t match what examiners award.

Avoid it

• Learn key definitions exactly (diffusion, isotope, oxidation, reduction, catalyst, neutralisation).
• Use the right command word style:
  • State: short fact
  • Describe: what you see / what changes
  • Explain: reason + science link

3) Losing easy marks in calculations

What happens: you know the chapter, still you lose 10–20 marks through method errors.

Common mistakes

• forgetting to balance the equation before mole ratio
• mixing cm³ and dm³
• missing units
• rounding too early
• using Mr wrong

Avoid it

• Use one fixed layout: balance → ratio → moles → convert → answer with units.
• Keep conversions beside you: 1000 cm³ = 1 dm³.

4) Weak bonding and structure explanations

What happens: students list properties without the reason, so marks are capped.

Avoid it

• Build “because” answers:
  • ionic: strong electrostatic attraction → high melting point
  • graphite: one electron per carbon delocalised → conducts
  • metals: delocalised electrons → conducts; layers slide → malleable

5) Guessing electrolysis products

What happens: electrolysis in aqueous solutions becomes a gamble.

Avoid it

• Always do: ions present → aqueous or molten → decide discharge → products at electrodes.
• Practise common cases until they’re automatic (brine, dilute acids, copper(II) sulfate).

6) Messy acids, bases, and salts methods

What happens: students choose the wrong preparation method and lose the whole question.

Avoid it

• Learn the decision rule:
  • soluble salt from acid + alkali → titration
  • soluble salt from acid + insoluble base/carbonate → excess solid, filter, crystallise
  • insoluble salt → precipitation, filter, wash, dry

7) Ignoring Paper 6 / practical skills

What happens: students leave 10–15 marks on the table in tables, graphs, errors, and improvements.

Avoid it

• Tables: headings + units, consistent decimal places.
• Graphs: correct scale, neat plots, best-fit line.
• Improvements: specific and realistic (repeat and average, insulate, use burette/pipette, lid to reduce heat loss).

8) Skipping qualitative analysis (tests for ions and gases)

What happens: students panic in easy recall questions.

Avoid it

• Keep one sheet for:
  • gas tests (H₂, O₂, CO₂, NH₃, Cl₂)
  • cations and anions tests
  • flame tests
• Self-test daily for five minutes.

9) Rushing papers without a plan

What happens: careless reading, missed command words, and lost marks in “easy” questions.

Avoid it

• Underline command words and data.
• For MCQs, eliminate wrong options, don’t guess instantly.
• For structured questions, write the equation first if any numbers appear.

10) Not fixing repeated mistakes

What happens: you keep losing marks in the same areas week after week.

Avoid it

• Keep a mistake log with: topic, error, correct method, one action to fix.
• Redo the same question type until you can’t get it wrong.

The pattern behind most fails

It’s rarely a lack of intelligence. It’s a lack of routine: consistent past-paper practice, strict marking, and targeted fixing. Get those three right, and Chemistry becomes predictable, which is exactly what you want in an exam.