IGCSE Chemistry Prerequisites: What You Need Before Starting 0620

IGCSE Chemistry 0620 does not assume much, but it does assume a few things fluently. Students who struggle in the first term often have not hit a wall of chemistry — they have hit maths they can do slowly but not quickly, or English demands they were not expecting. This page lists what you genuinely need in place before starting, so a transfer student, homeschooler or early beginner can shore up the gaps before they cost marks. It is written as readiness, not as a barrier: every item here is learnable, and it is far cheaper to build it now than mid-course.

Maths readiness

Chemistry uses school maths, but it uses it repeatedly, quickly and inside word problems. Slow-but-correct is not enough when a calculation is one part of a longer question under time pressure. Five areas matter most.

1. Rearranging simple formulae

You will use relationships such as moles = mass ÷ molar mass, and you will need to rearrange them to find any of the three quantities. If “make mass the subject” is not automatic, practise it before the mole topic arrives, because the mole calculations build directly on it.

2. Ratio and proportion

Balanced equations are ratios. “2 mol of this reacts with 1 mol of that” is a proportion problem, and reacting-mass and gas-volume calculations are proportion problems dressed in chemistry. Comfort with scaling ratios up and down is used in almost every calculation topic.

3. Standard form

Chemistry deals with very large and very small numbers — the Avogadro constant, tiny concentrations — and expects standard form (e.g. 6.02 × 10²³). You need to read it, write it, and enter it on a calculator correctly. A factor-of-ten slip from mishandling standard form is one of the most common avoidable calculation errors.

4. Percentages

Percentage composition, percentage yield and percentage purity all appear. You need to move confidently between a fraction, a decimal and a percentage, and to calculate “X as a percentage of Y” without hesitation.

5. Calculator fluency

A scientific calculator, used well, prevents errors. Know how to enter standard form, use brackets so a multi-step calculation evaluates in the right order, and round sensibly to significant figures. Fumbling the calculator wastes the seconds a timed paper does not give back.

None of this is beyond lower-secondary maths. The prerequisite is not difficulty; it is fluency, because Chemistry borrows the maths while your attention is on the chemistry.

Science background

A grounding in lower-secondary science makes the start smoother, though a determined beginner can build it as they go. The most useful prior ideas:

• The particle model — that matter is made of particles, and that their arrangement and movement explain solids, liquids and gases. This underlies states of matter and much of bonding.
• Basic chemical change — that substances can react to form new substances, and that mass and atoms are conserved.
• Elements, compounds and mixtures as distinct ideas, the foundation of atoms, elements and compounds.
• Simple lab familiarity — recognising common apparatus and the idea of a fair test — which helps with the practical component even before formal training.

A transfer or homeschool student without a formal science course is not blocked, but should plan to spend the first few weeks laying these foundations rather than assuming them. If Chemistry currently “feels hard”, the honest reasons and remedies are in is IGCSE Chemistry hard.

English and command-word readiness

This is the prerequisite students underestimate. IGCSE Chemistry is not only calculations — a large share of marks come from written answers that must say a precise thing in a precise way. Two demands follow.

Reading the question accurately. Questions hinge on small words — “not”, “least”, “per”, “excess” — and misreading one loses the mark regardless of your chemistry. Careful reading is a skill you can practise from day one.

Answering the command word. Each question uses a command word — state, describe, explain, compare, suggest, calculate — that dictates the kind of answer required. “Describe” and “explain” are different tasks, and answering one when the other is asked scores nothing. You do not need advanced English, but you do need enough to write a clear, specific sentence and to distinguish these instructions. The command-words guide is worth reading early, not late.

For students working in English as an additional language, the vocabulary load is real but bounded — it is technical terms, learned like any other content, not general fluency.

A quick self-check before you start

You are well prepared to begin 0620 if you can, without much hesitation:

• rearrange moles = mass ÷ molar mass to find mass
• scale a ratio such as 2 : 1 up and down
• write 0.00046 in standard form and enter it on a calculator
• find 12 as a percentage of 80
• explain, in a sentence, the difference between a solid and a gas in particle terms
• say what “describe” asks for versus “explain”

Gaps here are not a reason to delay — they are simply the first things to shore up, ideally before the calculation-heavy topics arrive.

Where prerequisites sit in the bigger plan

These foundations feed straight into the first term of the course. How they slot into a full year is mapped in the Year 10 IGCSE Chemistry roadmap, which sequences topics so the maths and science demands build in a sensible order. If you are also deciding between Core and Extended, note that Extended leans harder on the calculation prerequisites — see Core vs Extended.

Next steps

Shore up any gaps above, then use the free diagnostic to check your starting point across the topic notes, and practise the foundational calculation skills through the topical questions and practice hub.