CCEA AS Chemistry rewards precision as much as knowledge: titration calculations, mechanism arrows and enthalpy signs cost real marks every year. This page shows where the marks sit across all four units and how to use your time.
読了時間 4 分更新日: 2026年9月3日
試験の概要
試験数
4
満点
260
制限時間
5時間 30分
出題形式
12
試験
時間
配点
問題数
配点比率
出題形式
AS 1: Physical & inorganic chemistry
1時間 30分
90
15
34.6%
Multiple choice, Structured calculation and theory, Extended response (QWC)
AS 2: Organic & further physical chemistry
1時間 30分
90
16
34.6%
Multiple choice, Structured organic and physical chemistry, Extended response (QWC)
AS 3: Practical (hands-on)
1時間 15分
25
3
9.6%
Practical laboratory assessment
AS 3: Practical theory
1時間 15分
55
5
21.2%
Practical theory and stoichiometry
評価段階
ABCDEU
電卓の規定
A scientific calculator is expected for every paper in this subject. CCEA follows the JCQ rule that applies across all its exams: no calculator with a computer algebra system or symbolic manipulation function, no borrowing a calculator from another candidate, and nothing stored in memory that could be retrieved during the exam, including formulae, notes or text. If your calculator has an exam mode, switch it on. It clears stored data far more reliably than the reset button, which only resets the display settings and leaves any stored programs or text in memory.
AO1: AO1: demonstrate knowledge and understanding of scientific ideas, processes, techniques and procedures (33%)
AO2: AO2: apply that knowledge and understanding in theoretical and practical contexts and when handling qualitative and quantitative data (42%)
AO3: AO3: analyse, interpret and evaluate scientific information, ideas and evidence to make judgements and reach conclusions, and to develop and refine practical design and procedures (25%)
目的: Carries a titration result through moles, concentration and mass without retyping a rounded intermediate value, so rounding error does not creep into a three or four step calculation.
使う場面: Any titration or volumetric analysis question that chains two or more calculation steps together.
手順
Calculate moles from the titre as normal, then press the memory-store key (M+ or STO) instead of writing the rounded figure down. Move to the next step and press the memory-recall key (MR or RCL) to bring the exact value back in, then continue the calculation from there.
試験での注意: Use this only with values you calculate live in the exam. CCEA and JCQ ban anything stored in a calculator's memory before the exam, including formulae or old working, so clear your calculator's memory and switch on exam mode if it has one before you sit down.
Use standard form properly for Avogadro and concentration work
Casio fx-83/85 series (scientific)
目的: Stops a power of ten getting dropped or mistyped partway through a multi-step mole calculation.
使う場面: Any calculation involving Avogadro's constant, very small or very large concentrations, or an answer that must be given in standard form.
手順
Enter values such as 6.02 times 10 to the 23 using the calculator's power or EXP key rather than typing out the zeros by hand. Switch the calculator's display mode to scientific (SCI) before the final answer line if the question asks for standard form.
試験での注意: This is a live, in-exam technique, not a stored setting carried over from before the exam. Reset your calculator to its default state before the exam, then apply this as you work through each question.
Check the limiting reagent with fraction mode
Casio fx-83/85 series (scientific)
目的: Keeps a mole ratio exact so it is quicker and safer to see which reactant is short.
使う場面: Any question giving two known aqueous reactant quantities where you need to identify the limiting reactant before calculating a yield or excess.
手順
Work out moles of each reactant, then enter them as a fraction using the a-b/c key rather than converting to a rounded decimal first. Compare the fraction directly against the equation's mole ratio.
試験での注意: Use this as a working method during the exam only. No programme, formula list or previous working may be stored in the calculator going in, and a manual reset does not clear stored memory: use exam mode instead.
よくあるミス
1high影響する配点: 2Qualitative tests
Recording an observation as just 'a precipitate forms' or 'the solution goes cloudy' without stating a colour or the word precipitate.
回避方法: State the colour and the word precipitate together, for example 'a white precipitate forms', and if a colour changes, state both the starting and finishing colour.
2medium影響する配点: 2Halogens
In liquid-liquid extraction and halide displacement tests, describing only a colour change without saying that two distinct layers have formed or which layer carries the colour.
回避方法: Name both layers, upper organic and lower aqueous or the reverse, and state explicitly which one is coloured.
3high影響する配点: 1Energetics
Dropping the negative sign on exothermic enthalpy changes, for example writing 31.9 instead of -31.9 kJ per mole.
回避方法: Treat the sign as part of the answer rather than a formatting extra. Write it into your working the moment you decide the reaction is exothermic, before you round anything.
4medium影響する配点: 3Formulae, equations and amounts of substance
Not checking which reactant is limiting when a question gives two known aqueous quantities, and basing the whole calculation on the wrong one.
回避方法: Before calculating anything, work out moles of both reactants and compare against the equation's ratio to find the limiting one first.
5high影響する配点: 2Halogenoalkanes
Drawing curly arrows in SN1 and electrophilic addition mechanisms that start from open space near a bond rather than from the exact lone pair or bond centre.
回避方法: Start every arrow on a lone pair or the middle of the bond that breaks, and finish it exactly on the atom or new bond position.
6medium影響する配点: 2Equilibrium
Believing a catalyst increases the yield of a reaction rather than just the rate at which equilibrium is reached.
回避方法: State explicitly that a catalyst speeds up the forward and reverse reactions equally and does not change the position of equilibrium or the value of Kc.
7medium影響する配点: 2Formulae, equations and amounts of substance
Reading a graph gradient from a small triangle drawn close together on the line instead of using points that span most of the line's length.
回避方法: Pick two points as far apart as possible on the drawn line itself, not on the plotted data points, and show both coordinates in your working.