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.
根據歷屆試題與評分準則整理（2023–2025）。
計算機程式
Table mode for roots & turning points
Scientific calculator (e.g. Casio fx-991 series)
用途: Tabulate \(y\) across a range of \(x\) to locate sign changes (roots) and approximate maxima/minima.
使用時機: Solving or sketching a function when you want to find where its graph crosses or turns.
步驟
Enter the function in TABLE mode, set the start, end and step, then read where the sign of \(y\) changes or where it peaks.
考試提示: 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)
用途: Read the mean \(\bar{x}\) and standard deviation directly, and the gradient/intercept (and \(r\)) of a linear regression for bivariate data.
使用時機: Any data-handling, statistics, or required-practical analysis question.
步驟
Enter the data in STAT mode (1-VAR or A+BX), then recall \(\bar{x}\), \(\sigma\) or the regression coefficients.
考試提示: 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)
用途: Keep full-precision intermediate values to avoid rounding errors.
使用時機: Multi-step calculations where premature rounding loses the final accuracy mark.
步驟
Use Ans, STO/RCL or the M+ memory to reuse the unrounded result of each step; round only the final answer.
考試提示: 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)
用途: Use the built-in EQN/SOLVE mode to verify roots of quadratics or simultaneous equations you have already solved by algebra.
使用時機: As a check only, after solving by hand.
步驟
Enter the coefficients in EQN mode (or use SOLVE) and confirm they match your worked solution.
考試提示: Allowed, but clear stored programs/data (graphical calculators in exam mode) and show the required working — unsupported calculator answers score no method marks.
常見錯誤
1high涉及分數: 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).
如何避免: 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涉及分數: 1Energetics (Physical chemistry)
Forgetting to include the negative sign (-) when writing calculated exothermic enthalpy changes (ΔH) or molar enthalpy values.
如何避免: 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.
如何避免: Ensure you refer to the starting materials as ions (e.g., 'astatide ions lose electrons' or 'chlorine displaces bromide ions' rather than 'bromine').
4high涉及分數: 2Chemical tests (Inorganic chemistry)
Failing to write down both the method and the expected observation when asked to describe a qualitative chemical test.
如何避免: 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涉及分數: 2Covalent bonding (Principles of chemistry)
Claiming that strong covalent bonds break when simple molecular covalent substances boil or melt.
如何避免: 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涉及分數: 1Reactivity series (Inorganic chemistry)
Stating that zinc 'rusts' instead of iron when describing sacrificial protection.
如何避免: Specify that zinc 'oxidises', 'corrodes', or 'reacts' in preference to iron. Remember that 'rusting' is a term reserved strictly for iron.