An evidence-based preparation guide for Pearson Edexcel International GCSE Chemistry (4CH1). It outlines core paper weightings, high-impact strategies to master stoichiometry and energetics calculations, key terminology expectations, and how to avoid the most common examiner-flagged mistakes.
A scientific or graphical calculator is permitted. Graphical calculators must be in exam mode with all stored programs and data cleared before the exam; the calculator must not be able to retrieve stored text or formulae.
過去問と採点基準にもとづいて作成（2023–2025）。
電卓プログラム
Table mode for roots & turning points
Scientific calculator (e.g. Casio fx-991 series)
目的: Tabulate \(y\) across a range of \(x\) to locate sign changes (roots) and approximate maxima/minima.
使う場面: Solving or sketching a function when you want to find where its graph crosses or turns.
手順
Enter the function in TABLE mode, set the start, end and step, then read where the sign of \(y\) changes or where it peaks.
試験での注意: Allowed, but clear stored programs/data (graphical calculators in exam mode) and show the required working — unsupported calculator answers score no method marks.
Statistics mode (mean, SD & regression)
Scientific calculator (e.g. Casio fx-991 series)
目的: Read the mean \(\bar{x}\) and standard deviation directly, and the gradient/intercept (and \(r\)) of a linear regression for bivariate data.
使う場面: Any data-handling, statistics, or required-practical analysis question.
手順
Enter the data in STAT mode (1-VAR or A+BX), then recall \(\bar{x}\), \(\sigma\) or the regression coefficients.
試験での注意: Allowed, but clear stored programs/data (graphical calculators in exam mode) and show the required working — unsupported calculator answers score no method marks.
Carry exact values with Ans & memory
Scientific calculator (e.g. Casio fx-991 series)
目的: Keep full-precision intermediate values to avoid rounding errors.
使う場面: Multi-step calculations where premature rounding loses the final accuracy mark.
手順
Use Ans, STO/RCL or the M+ memory to reuse the unrounded result of each step; round only the final answer.
試験での注意: Allowed, but clear stored programs/data (graphical calculators in exam mode) and show the required working — unsupported calculator answers score no method marks.
Equation solver — to CHECK your working
Scientific calculator (e.g. Casio fx-991 series)
目的: Use the built-in EQN/SOLVE mode to verify roots of quadratics or simultaneous equations you have already solved by algebra.
使う場面: As a check only, after solving by hand.
手順
Enter the coefficients in EQN mode (or use SOLVE) and confirm they match your worked solution.
試験での注意: Allowed, but clear stored programs/data (graphical calculators in exam mode) and show the required working — unsupported calculator answers score no method marks.
よくあるミス
1high影響する配点: 2Chemical formulae, equations and calculations (Principles of chemistry)
Rounding intermediate decimal steps too early in calculations (e.g., truncating 0.00409 to 0.004 in a multi-step stoichiometry calculation).
回避方法: Keep the full decimal values stored in your calculator memory (using store/recall functions) and round only the final answer to 3 significant figures.
2high影響する配点: 1Energetics (Physical chemistry)
Forgetting to include the negative sign (-) when writing calculated exothermic enthalpy changes (ΔH) or molar enthalpy values.
回避方法: Always explicitly write the negative sign (-) for exothermic reactions (e.g. -95 kJ/mol) when asked to 'include a sign in your answer'.
Confusing the halogen elements with their respective halide ions during explanations of displacement and redox reactions.
回避方法: Ensure you refer to the starting materials as ions (e.g., 'astatide ions lose electrons' or 'chlorine displaces bromide ions' rather than 'bromine').
Failing to write down both the method and the expected observation when asked to describe a qualitative chemical test.
回避方法: Include the reactant/reagent added and the precise final observation (e.g., to test for chloride: add nitric acid and silver nitrate solution to get a white precipitate).
5high影響する配点: 2Covalent bonding (Principles of chemistry)
Claiming that strong covalent bonds break when simple molecular covalent substances boil or melt.
回避方法: State clearly that only the weak intermolecular forces of attraction between molecules are broken/overcome during melting and boiling, whilst the covalent bonds within the molecules remain intact.
6medium影響する配点: 1Reactivity series (Inorganic chemistry)
Stating that zinc 'rusts' instead of iron when describing sacrificial protection.
回避方法: Specify that zinc 'oxidises', 'corrodes', or 'reacts' in preference to iron. Remember that 'rusting' is a term reserved strictly for iron.