Exam Technique and Past Paper Strategy

Chemistry rewards precise wording more than almost any other subject. This page collects the advice that came up most often across a large set of one-to-one lessons.

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1. Learn the wording, not just the idea

Chemistry mark schemes are built around specific phrases. Knowing the concept is not enough if you cannot express it.

The phrases that repeatedly earn marks:

Topic	The phrase
Ionic bonding	”electrostatic force of attraction between oppositely charged ions”
Metallic bonding	”delocalised electrons”
Graphite	”free moving, delocalised electrons”
Giant covalent	”strong covalent bonds throughout the structure”
Simple molecular	”weak intermolecular forces between molecules”
Ionic conductivity	”the ions are free to move”
Equilibrium	”the rates of the forward and reverse reactions are equal”
Activation energy	”the minimum energy”
Diffusion	”random motion”, “concentration gradient”

“Use the specification for definitions and key terms” — tutors’ own advice. The syllabus wording is the mark scheme wording.

Focus on HOW to write the answer, not only on studying the content — flagged directly. Many students know the chemistry and lose marks on expression.

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2. Show your working in calculations

Marks are awarded for the METHOD, not just the answer.

For every calculation:

1. Write the balanced equation if one is involved
2. Convert units first — cm³ to dm³, g to kg
3. Find the MOLES before anything else
4. Show the mole ratio
5. Give the answer with units and sensible significant figures

“Always find the number of moles first” was said in almost identical words in several lessons. It is the single most useful habit in Chemistry calculations.

Write down equations to gain marks — even an unbalanced equation with the correct reactants and products earns credit.

Use standard form for large numbers, and give a quantitative answer where the question asks you to compare.

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3. Command words

Command	What it requires
State / Give / Name	a short factual answer — no explanation needed
Describe	say what happens — observations, steps
Explain	say why — give reasons and mechanisms
Suggest	apply your knowledge to an unfamiliar situation
Predict	say what will happen, with a brief reason
Calculate	show working, give units
Define	the exact wording

“Describe” and “explain” are different. A description of a colour change is not an explanation of why it happens — and answering the wrong one wastes time and earns nothing.

Match the detail to the marks. A 3-mark explanation needs three distinct points. Look at the allocation before deciding how much to write.

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4. Recall you simply need

Some things cannot be worked out and must be memorised:

• Ion charges and the common polyatomic ions
• The reactivity series
• Solubility rules
• Flame test colours and precipitate colours
• Ion and gas tests — reagent, observation, conclusion
• Indicator colours
• Conditions for the Haber and Contact processes, cracking and fermentation
• Organic general formulae and functional groups

Practise balancing equations and the calculation types — concentration, empirical formula, molecular formula — which tutors named as high-yield.

Focus on functional groups and their properties in organic questions — also flagged directly.

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5. The papers

Cambridge IGCSE Chemistry is assessed across multiple-choice, theory and practical papers. Check your own timetable for which you sit.

Multiple choice — around 40 questions in 40 minutes, so roughly one minute each. Attempt every question; there is no penalty for a wrong answer. Eliminate obviously wrong options first, and mark any you guessed to revisit.

Theory papers — structured questions with short answers and calculations. Read twice, note the command word, and answer what is asked.

The practical paper (alternative to practical) — experimental setups, variables, tables, graphs and sources of error.

Naming independent, dependent and control variables — with quantifiable values — is crucial for the practical paper. Tutors flagged this as the highest-value habit for that paper.

Never write “human error” — name the specific mechanism.

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6. Using past papers

The most consistent advice across every tutor.

How to work through one:

1. Do it timed, in one sitting
2. Do not look at your notes while doing it
3. Complete the whole paper before checking the mark scheme
4. Mark it yourself and study the mark scheme wording
5. Log every question you got wrong, and redo it later

“Avoid referring to notes during practice exams” and “complete the paper before checking the mark scheme” were both stated directly. Checking as you go feels productive but hides what you actually don’t know.

Practise answering from memory to build recall — reading alone does not.

Reading textbooks alone is not effective — tutors recommended summary notes and active recall instead.

Use the syllabus as a CHECKLIST to confirm you have covered every topic. Past papers show what has been asked; only the syllabus shows what could be.

Setting a target: one tutor suggested aiming for 35–36 out of 40 on the multiple choice as a strong-grade benchmark. Use recent papers, and cover different variants.

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7. In the exam

• Read each question twice before answering
• Underline the key information
• State assumptions clearly where a question is open
• Use the graph or data given — if a question provides one, it expects you to use it
• Check units on every numerical answer
• Sanity-check: no yields above 100%, no negative masses, no pH outside 0–14
• Avoid careless mistakes — the commonest cause of lost marks at every grade

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8. Before you hand in

• Every question attempted
• Working shown for every calculation
• Units on every numerical answer
• Equations balanced, with state symbols where needed
• Definitions written in the specification’s wording
• Explanations give the mechanism, with enough points for the marks
• Graphs: axes labelled with units, sensible scale, crosses, best-fit line
• Observations include colour changes and gas tests
• Answers sanity-checked

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Frequently asked questions

How important is exact wording? Very — Chemistry mark schemes are built on specific phrases.

Where do I find the right wording? The syllabus (specification) — use it for definitions and key terms.

Do I get marks for working? Yes — method marks are awarded even if the final answer is wrong.

What’s the first step in a calculation? Convert the units, then find the moles.

What’s the difference between describe and explain? Describe says what happens; explain says why.

How much should I write? Match the number of marks — three marks means three distinct points.

How should I use past papers? Timed, without notes, completing the whole paper before checking the mark scheme.

Is reading the textbook enough? No — use summary notes and practise from memory.

What matters most on the practical paper? Variables with quantifiable values, accurate readings, and specific sources of error.

Is there negative marking? No — attempt every question.

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This page covers exam technique for Cambridge IGCSE Chemistry (0620) and is written for Grade 9–11 / Year 10–11 students. It is based on the advice given most often across a large set of one-to-one IGCSE Chemistry lessons, together with how Cambridge mark schemes allocate marks. Paper numbering and structure vary by syllabus version and tier — always check the current syllabus and your own exam timetable.