An A* in IGCSE Chemistry (0620) is built on three things: rock-solid fundamentals, fast and accurate exam technique, and enough past-paper practice to spot patterns before you even finish reading a question. Chemistry isn’t about learning huge chunks once; it’s about revisiting the same ideas until they feel automatic under pressure.

This guide covers what to revise, how the exam tests you, and the habits that separate strong students from top scorers.

Know the exam papers you’ll sit

Your combination depends on Core or Extended, and whether your school enters you for Practical or Alternative to Practical. The key point: the exam rewards more than memory.

You’ll be tested on:

• Knowledge and understanding (definitions, facts, concepts)
• Application and problem-solving (calculations, unfamiliar contexts, data)
• Practical skills (methods, observations, analysis, improvements)

So, your revision plan needs content + questions + practical thinking.

The content map: what the syllabus keeps returning to

If you revise these areas properly, you cover the bulk of what appears again and again:

1) Particles, states, and separation

• Particle model, diffusion, changes of state
• Pure substances vs mixtures
• Filtration, crystallisation, simple distillation, fractional distillation, chromatography

A habit:* link each separation method to the property it uses (boiling point, solubility, particle size, attraction to the stationary phase).

2) Atoms, elements, compounds, and bonding

• Atomic structure, isotopes, ions, electron arrangement
• Ionic, covalent, metallic bonding
• Giant ionic, giant covalent, simple molecular structures
• Properties linked to structure (melting point, conductivity, hardness)

A habit:* don’t memorise properties as a list; explain them using particles and bonding.

3) Stoichiometry (the marks engine)

• Formulae, balancing equations
• Relative atomic mass and molar mass
• Moles and reacting mass calculations
• Concentration (including solutions)
• Gas volume calculations (where required)
• Limiting reactants, percentage yield, percentage purity

A habit:* use the same set-up every time: balanced equation → mole ratio → convert units → solve → units + sensible rounding.

4) Chemical reactions and patterns

• Exothermic/endothermic ideas, energy changes
• Rates and catalysts, interpreting graphs
• Reversible reactions and equilibrium (where covered)
• Redox basics and oxidation numbers

A habit:* practise describing graphs in words that match mark schemes: “rate increases”, “steeper gradient”, “levels off”, “constant mass”.

5) Acids, bases, and salts

• pH, indicators, acid/base definitions
• Neutralisation, ionic equations
• Preparing salts (titration, excess insoluble base, precipitation)
• Solubility rules and identifying precipitates

A habit:* learn salt preparation as a decision tree: soluble salt from acid + alkali needs titration; insoluble base/carbonate can be used in excess; insoluble salts come from precipitation.

6) Periodic Table and trends

• Group 1 trends, Group 7 trends
• Noble gases
• Transition metals (general properties)
• Reactivity patterns linked to electron structure

A habit:* always explain trends using electron shells and nuclear attraction, not “it reacts more because it reacts more”.

7) Metals and extraction

• Reactivity series and displacement
• Rusting and prevention
• Extraction ideas (carbon reduction vs electrolysis)
• Alloys and why they are useful

A habit:* when extraction is asked, state why a method is used based on reactivity.

8) Organic chemistry

• Alkanes, alkenes, polymers
• Fuels, cracking
• Alcohols and carboxylic acids (where covered)
• Writing and naming structures

A habit:* practise drawing and naming until it’s quick. Most mistakes are simple: missing bonds, wrong suffix, wrong functional group.

9) Environmental chemistry and analysis

• Air and water pollutants
• Treatment of water, fertilisers, basic industrial chemistry themes
• Tests for ions and gases, flame tests
• Chromatography interpretation

A habit:* keep qualitative tests on one sheet and test yourself daily for five minutes.

Practical / Alternative to Practical: the easiest marks to secure

These questions reward clear scientific thinking.

Train these skills:

• Choosing suitable apparatus and reading scales correctly
• Variables: independent, dependent, control
• Table layout with headings and units
• Graphs: correct axes, sensible scales, neat plotting, line of best fit
• Evaluation: sources of error, realistic improvements

Write improvements that change the method, not vague wishes. “Repeat and take an average” works. “Use a more accurate measuring cylinder” doesn’t, since the better upgrade is a burette or pipette, depending on the task.

Past-paper strategy that gets A* results

Past papers aren’t revision after revision; they are the revision.

Use this three-step loop:

1. Topical practice right after learning a topic (short sets)
2. Mixed questions once you’ve covered several topics
3. Full timed papers in the final phase

After marking, create a mistake log with:

• Topic
• What went wrong (concept gap, method issue, rushed reading)
• Fix (a single action: redo five similar questions, rewrite definition, drill a calculation type)

Do not just read the mark scheme. Rewrite your final answer in clean exam wording.

A simple weekly structure (repeat this)

• 3 days content + topical questions
• 2 days mixed questions
• 1 day timed paper
• 1 day review + mistake-log fixes

Keep sessions focused: one topic, one skill type, one timed block.

Exam technique checklist (small habits, big marks)

• Underline command words: state, explain, describe, calculate, suggest
• Write units on every calculation line
• Balance equations before using mole ratios
• If a question asks for an observation, give what you would see (colour change, gas, precipitate), not the theory
• If asked to “explain”, include the reason linked to particles, electrons, or energy

The A* standard, in one sentence

If you can explain every core idea simply, set up every calculation the same way, and stay calm through unfamiliar contexts because you’ve practised patterns, an A* becomes the expected outcome rather than the lucky one.