Pearson Edexcel IGCSE Chemistry: Paper-by-Paper Exam Preparation

Pearson Edexcel International GCSE Chemistry 4CH1 is a linear, untiered qualification with two externally assessed written papers taken in the same series. Paper 1 lasts 2 hours, carries 110 marks and is worth 61.1% of the qualification; Paper 2 lasts 1 hour 15 minutes, carries 70 marks and is worth 38.9%. The distinction between them is not topic-based but depth-based: Paper 1 assesses only the core, non-bold-referenced content, while Paper 2 assesses all content including the bold-referenced material. These notes complement the site’s guides to Principles of Chemistry and Reactivity and Group Trends.

The bold-referenced content is Paper 2’s alone – know which statements those are

This is the structural fact that governs everything else. The specification marks certain statements in bold; those statements can appear on Paper 2 and cannot appear on Paper 1. Exam-preparation priority: go through the specification and physically mark the bold statements, then keep two revision lists. Preparing for Paper 2 as though it were simply “more of Paper 1” misses the point: Paper 2 is where the extension material lives, and it is where the grade at the top end is decided.

Paper 1 carries 110 of the 180 marks – the core content is not the easy part

Because the bold content feels harder, it attracts disproportionate attention. But the core content is worth 110 marks on Paper 1 and is also examinable on Paper 2. Exam-preparation priority: secure the core thoroughly first. Every core topic contributes to both papers, while a bold-referenced topic contributes only to Paper 2’s 70 marks.

Paper 2’s shorter clock is tighter per mark

Paper 1 gives 120 minutes for 110 marks (about 1.1 minutes per mark); Paper 2 gives 75 minutes for 70 marks (about 1.07). Both are brisk, and Paper 2’s brevity is easy to underestimate because the paper looks shorter. Exam-preparation priority: practise Paper 2 as a complete timed unit rather than as a set of questions, so that the pace becomes familiar.

Calculation questions are where method marks are won and lost

Chemistry calculations – moles, concentration, yield, empirical formulae, gas volumes – carry method marks that are only awardable when the working is visible. Exam-preparation priority: write the relationship being used before substituting numbers, every time. A bare wrong answer earns nothing; the same wrong answer with the relationship and substitution shown usually earns most of the marks.

Practical questions test method and evaluation, not just recall

The specification’s required practical work is assessed in the written papers, and the questions typically ask about apparatus choice, control of variables, sources of error and improvements rather than about the result. Exam-preparation priority: for each practical you have carried out, write three lines from memory – what was measured, what was controlled, and what the main source of error was. That trio answers most practical questions; a recollection of the result alone answers very few.

Worked routine: setting out a mole calculation for full method marks

The routine below is an original model written for this resource, not a reproduction of any official past paper or mark scheme.

Step 1 - write what you are finding and its unit:
"n(NaOH) = ... mol" before any arithmetic.

Step 2 - write the relationship, not just the numbers:
n = c x V/1000  (or  n = m / Mr)
Showing the relationship is what carries the method mark.

Step 3 - substitute with units visible:
n = 0.100 x 25.0/1000 = 2.50 x 10^-3 mol

Step 4 - use the balanced equation ratio explicitly:
State the mole ratio you are applying -- "1:1 from the equation,
so n(HCl) = 2.50 x 10^-3 mol" -- rather than moving straight to
the next number.

Step 5 - check significant figures and the plausibility of the
answer:
Match the data's precision, and ask whether the magnitude makes
sense (a concentration of 4,000 mol/dm3 is a slipped decimal).

Step 4 is the step most often compressed away, and it is frequently a mark in its own right.

Before/during exam checklist

• Before the exams: mark the bold-referenced statements in the specification and keep a separate Paper 2 list; secure the core content first, since it counts towards both papers; practise Paper 2 as a complete timed unit; write three lines from memory (measured, controlled, main error) for each required practical.
• During either paper: budget roughly one minute per mark and keep moving.
• In every calculation: state the quantity, write the relationship, substitute with units, state the mole ratio explicitly, then check significant figures and plausibility.
• On practical questions: answer about method, control and error rather than about the result.

Self-test

1. What is the actual difference in scope between Paper 1 and Paper 2?
2. Why should the core content be secured before the bold-referenced content?
3. Which step of a mole calculation is most often compressed away, and why does it matter?
4. What three things should a practical revision note contain?

Answers: 1. Paper 1 assesses only the core, non-bold-referenced content; Paper 2 assesses all content, including the bold-referenced extension material – the split is by depth, not by topic. 2. Because core content is examinable on both papers (110 marks on Paper 1 plus availability on Paper 2), while bold-referenced content contributes only to Paper 2’s 70 marks. 3. Stating the mole ratio from the balanced equation explicitly – it is frequently a mark in its own right and is easily lost by moving straight to the next number. 4. What was measured, what was controlled, and what the main source of error was.

Written against the Pearson Edexcel International GCSE Chemistry 4CH1 specification (official specification PDF, verified 2026-08-28). The calculation routine above is an original model written for this resource, not a reproduction of any official past paper or mark scheme. Always check the current specification for your examination year at qualifications.pearson.com.