Twenty First Century Science - Chemistry B - J258 試験対策
Master the OCR GCSE (9-1) Chemistry B (Twenty First Century Science) J258 syllabus with our expert guide. Discover high-yielding exam strategies, master quantitative conversions, and avoid common pitfalls highlighted in official examiner reports to secure your Grade 9.
読了時間 4 分更新日: 2026年6月21日
試験の概要
試験数
2
満点
180
制限時間
3時間 30分
出題形式
4
試験
時間
配点
問題数
配点比率
出題形式
Paper 3: Breadth in Chemistry (Higher Tier)
1時間 45分
90
32
50%
Multiple Choice / Tick Box, Short Answer / Structured, Calculations
Paper 4: Depth in Chemistry (Higher Tier)
1時間 45分
90
31
50%
Multiple Choice / Tick Box, Short Answer / Structured, Calculations, Level of Response (Extended Writing)
評価段階
987654321
電卓の規定
A scientific or graphical calculator that meets JCQ regulations may be used (some GCSE Mathematics and Science papers are non-calculator). Graphical calculators must be set to exam mode; you must clear any stored programs, notes or data before the exam, and the calculator must not be able to retrieve stored text or formulae.
AO1: AO1: Demonstrate knowledge and understanding of scientific ideas and scientific techniques and procedures. (40%)
AO2: AO2: Apply knowledge and understanding of scientific ideas and scientific enquiry, techniques and procedures. (40%)
AO3: AO3: Analyse information and ideas to interpret and evaluate, make judgements and draw conclusions and develop and improve experimental procedures. (20%)
過去問と採点基準にもとづいて作成（2022–2024）。
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 under JCQ rules, but you must still show your method — an unsupported calculator answer earns no method marks. Clear all stored programs, notes and data (graphical calculators in exam mode) before the exam.
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 under JCQ rules, but you must still show your method — an unsupported calculator answer earns no method marks. Clear all stored programs, notes and data (graphical calculators in exam mode) before the exam.
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 under JCQ rules, but you must still show your method — an unsupported calculator answer earns no method marks. Clear all stored programs, notes and data (graphical calculators in exam mode) before the exam.
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 under JCQ rules, but you must still show your method — an unsupported calculator answer earns no method marks. Clear all stored programs, notes and data (graphical calculators in exam mode) before the exam.
よくあるミス
1high影響する配点: 2How do bonding and structure affect properties of materials? (Material choices)
Incorrectly stating that 'covalent bonds' break when simple molecular substances like carbon dioxide melt or boil.
回避方法: Explicitly state that covalent bonds within the molecules are strong and remain intact; it is the weak intermolecular forces between the molecules that are overcome.
2high影響する配点: 2What are the different types of polymers? (Material choices)
Retaining carbon-carbon double bonds (C=C) inside brackets when drawing the repeating unit of an addition polymer.
回避方法: Always show the carbon backbone with a single bond (C-C) and draw open continuation bonds extending beyond the brackets.
3medium影響する配点: 1How are the amounts of substances in reactions calculated? (Chemical analysis)
Suggesting Universal Indicator for a titration instead of single-step indicator alternatives like phenolphthalein or methyl orange.
回避方法: Always specify a single-stage indicator (e.g., phenolphthalein which turns from pink to colourless) to observe a sharp, distinct end-point.
4high影響する配点: 2How do chemists control the rate of reactions? (Making useful chemicals)
Stating that concentration increases particle energy or speed when explaining its effect on reaction rate.
回避方法: Explain that concentration increases the number of particles per unit volume, which increases the frequency of collisions. Only temperature increases particle kinetic energy.
5medium影響する配点: 1Why are there temperatures changes in chemical reactions? (Air and water)
Forgetting the negative sign in bond energy calculations for exothermic reactions.
回避方法: Subtract energy of bonds formed from bonds broken. If products have more bond energy, the result is exothermic and must have a negative sign (e.g. -490 kJ).
6medium影響する配点: 2How are the atoms held together in a metal? (Chemicals of the natural environment)
Stating that alloys are harder because they form 'stronger chemical bonds'.
回避方法: State that alloys contain different-sized atoms that disrupt the regular layers of the metal lattice, preventing the layers from sliding over each other.