📚 Exam Sprint Notes for IB & AQA Science | IB AQA 科学考前冲刺笔记
Whether you are taking IB Sciences (Biology, Chemistry, Physics) or AQA GCSE / A‑level Science, the final weeks before the exam demand sharp, targeted revision. These sprint notes condense the most frequently tested cross‑topic concepts, essential equations, and exam‑winning strategies. Use them to reinforce your recall, spot common pitfalls, and walk into the exam hall with confidence.
无论你参加的是IB科学（生物、化学、物理）还是AQA的GCSE/A‑level科学考试，考前最后几周都需要精准、高效的复习。这份冲刺笔记浓缩了最常考到的跨学科核心概念、必备公式和应试策略，帮助你巩固记忆、避开常见陷阱，自信步入考场。
1. Scientific Method & Variables | 科学方法与变量识别
The independent variable is the one you change deliberately; the dependent variable is what you measure as a result. All other variables must be kept constant (controlled variables) to ensure a fair test. In an IB internal assessment or AQA required practical, you will be asked to write a clear hypothesis using ‘if … then … because …’ and to identify sources of systematic and random error.
自变量是你特意改变的因素，因变量是你因此测量的结果。所有其他变量必须保持不变（控制变量），以确保实验的公平性。在IB内部评估或AQA要求完成的实验中，你需要用“如果……那么……因为……”的形式写出清晰的假设，并识别系统误差和随机误差的来源。
- Accuracy: how close a measurement is to the true value. Precision: the closeness of repeated measurements.
- 准确度：测量值接近真实值的程度；精密度：多次测量结果的接近程度。
- A zero error in a meter is a systematic error; a human reaction time scatter is random.
- 仪表零位误差属于系统误差；人的反应时间分散属于随机误差。
2. Data Presentation & Error Analysis | 数据呈现与误差分析
Plot the independent variable on the x‑axis and dependent on the y‑axis. Label axes with quantity / unit, use linear scales, and draw a best‑fit line or curve. In IB and AQA, you are often required to calculate the percentage uncertainty: (absolute uncertainty ÷ measured value) × 100%. When combining uncertainties, add absolute uncertainties for addition/subtraction, add percentage uncertainties for multiplication/division.
将自变量画在x轴，因变量画在y轴。轴标签采用“物理量/单位”格式，使用线性刻度，并绘制最佳拟合线或曲线。在IB和AQA中，经常要求计算百分不确定度：(绝对不确定度 ÷ 测量值) × 100%。当合成不确定度时，加减运算用绝对不确定度相加，乘除运算用百分不确定度相加。
| Operation / 运算 | Uncertainty rule / 不确定度规则 |
|---|---|
| y = a + b | Δy = Δa + Δb |
| y = a × b | %εy = %εa + %εb |
| y = aⁿ | %εy = n × %εa |
3. Mechanics – Core Equations | 力学核心公式
Master the SUVAT equations for uniform acceleration. They apply equally in IB Physics and AQA Physics: v = u + at, s = ut + ½at², v² = u² + 2as, s = (u+v)t/2. Always choose the equation that omits the quantity you do not need. Remember that acceleration due to gravity g = 9.81 m s⁻² on Earth.
掌握匀加速运动的SUVAT公式。它们同样适用于IB物理和AQA物理：v = u + at，s = ut + ½at²，v² = u² + 2as，s = (u+v)t/2。总是选择不包含你不需要那项物理量的方程。记住地球表面重力加速度 g = 9.81 m s⁻²。
The resultant force F = ma, and for moments (torque): moment = force × perpendicular distance from pivot. In equilibrium, sum of clockwise moments = sum of anticlockwise moments.
合力 F = ma，力矩 = 力 × 到支点的垂直距离。在平衡状态下，顺时针力矩总和等于逆时针力矩总和。
4. Energy – Conservation & Efficiency | 能量守恒与效率
Energy cannot be created or destroyed, only transferred, stored or dissipated. Useful equations: kinetic energy Eₖ = ½mv², gravitational potential energy ΔEₚ = mgΔh, work done W = Fd cosθ. In IB and AQA exams, efficiency is often calculated as (useful output ÷ total input) × 100%, or for a heat engine (W_out ÷ Q_in).
能量既不能被创造也不能被消灭，只能被转移、储存或耗散。常用公式：动能 Eₖ = ½mv²，重力势能变化 ΔEₚ = mgΔh，做功 W = Fd cosθ。在IB和AQA考试中，效率常按 (有用输出 ÷ 总输入) × 100% 计算，或对于热机 (W_out ÷ Q_in)。
In Sankey diagrams, the width of arrows represents energy quantities; always check that the total input equals the sum of outputs.
在桑基图中，箭头宽度代表能量大小；始终检查总输入等于各输出之和。
5. Atomic Structure & Periodic Trends | 原子结构与元素周期律
Atoms consist of protons (relative mass 1, charge +1), neutrons (1, 0) and electrons (1/1836, –1). Atomic number Z = number of protons; mass number A = protons + neutrons. Isotopes have the same Z but different A. Electron configuration in IB and AQA follows the principle: 2,8,8… up to Z=20, then subshells s,p,d.
原子由质子（相对质量1，电荷+1）、中子（1，0）和电子（1/1836，–1）构成。原子序数 Z = 质子数；质量数 A = 质子数 + 中子数。同位素具有相同Z但不同A。IB和AQA中的电子排布遵循：2,8,8……直到Z=20，之后引入亚层s,p,d。
Periodic trends: atomic radius decreases across a period (increased nuclear charge) and increases down a group. Ionisation energy increases across a period and decreases down a group. Electronegativity follows the same trend as ionisation energy.
周期律：原子半径在同一周期从左到右递减（核电荷增加），同族由上至下递增。电离能同周期递增，同族递减。电负性与电离能趋势相同。
6. Bonding & Intermolecular Forces | 化学键与分子间作用力
Ionic bonding: transfer of electrons, giant lattice, high melting point, conducts when molten or dissolved. Covalent bonding: sharing of electrons; simple molecular substances have low melting points, while giant covalent (diamond, SiO₂) are very hard. Metallic bonding: sea of delocalised electrons, malleable, conductive.
离子键：电子转移，巨型晶格，高熔点，熔融态或溶于水时导电。共价键：电子共用；简单分子物质具有低熔点，而巨型共价结构（金刚石、SiO₂）非常坚硬。金属键：离域电子的海洋，可延展，能导电。
Intermolecular forces: London dispersion forces < dipole‑dipole < hydrogen bonding. Hydrogen bonding occurs when H is bonded to N, O, or F and explains water's high boiling point.
分子间作用力：伦敦色散力 < 偶极‑偶极作用 < 氢键。氢键发生在H与N、O或F成键时，解释了水的高沸点。
7. Cells & Membrane Transport | 细胞与膜运输
Prokaryotic cells lack a nucleus; eukaryotic cells have membrane‑bound organelles. Both IB and AQA require you to label a typical plant or animal cell: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, and for plants – cell wall, chloroplasts, vacuole.
原核细胞没有细胞核；真核细胞拥有具膜细胞器。IB和AQA都要求你标注典型的植物或动物细胞：细胞核、细胞质、细胞膜、线粒体、核糖体，植物细胞还包括细胞壁、叶绿体、液泡。
Passive transport (diffusion, osmosis, facilitated diffusion) does not require ATP. Active transport moves substances against the concentration gradient using ATP. Osmosis is the net movement of water across a partially permeable membrane from a region of higher water potential to lower water potential.
被动运输（扩散、渗透、协助扩散）不需要ATP。主动运输消耗ATP，将物质逆浓度梯度转运。渗透是水通过部分透膜从较高水势区域向较低水势区域的净运动。
8. Genetics – Key Terminology & Monohybrid Crosses | 遗传学关键术语与单基因杂交
Allele: version of a gene. Genotype: combination of alleles. Phenotype: observable characteristic. Homozygous: two identical alleles. Heterozygous: two different alleles. Dominant allele masks recessive in heterozygote.
等位基因：基因的变体形式。基因型：等位基因的组合。表现型：可观察到的特征。纯合：两个相同的等位基因。杂合：两个不同的等位基因。显性等位基因在杂合子中掩盖隐性等位基因。
Monohybrid cross Punnett square: predict ratios. For a cross of Aa × Aa, expected phenotype ratio is 3 dominant : 1 recessive. In IB, you also need to understand codominance and sex‑linked inheritance.
单基因杂交庞纳特方格：预测比例。Aa × Aa 杂交，预期表现型比例为 3 显性 : 1 隐性。在IB中，你还需要理解共显性和伴性遗传。
9. Electricity & Circuits | 电学与电路
Charge Q = It, voltage V = IR, power P = IV = I²R = V²/R. In series circuits, current is the same everywhere; voltage splits. In parallel circuits, current splits, voltage is the same across each branch. Pay attention to the difference between alternating current (AC) and direct current (DC) when drawing oscilloscope traces.
电荷 Q = It，电压 V = IR，功率 P = IV = I²R = V²/R。串联电路中各处电流相等，电压分配；并联电路中电流分配，各支路电压相等。在画示波器迹线时，注意交流电 (AC) 与直流电 (DC) 的区别。
Resistance increases with temperature in metals; in a filament lamp, the I‑V graph curves. A diode only allows current in one direction. Know how to calculate total resistance: series R = R₁ + R₂, parallel 1/R = 1/R₁ + 1/R₂.
金属的电阻随温度升高而增加；灯丝的I‑V图呈曲线。二极管只允许单向电流。掌握总电阻计算：串联 R = R₁ + R₂，并联 1/R = 1/R₁ + 1/R₂。
10. Chemical Calculations – Mole Concept | 化学计算与摩尔概念
The mole links mass and number of particles. n = m/M, where M is molar mass (g mol⁻¹). Concentration c = n/V (volume in dm³). At room temperature and pressure, 1 mol of gas occupies 24 dm³. Use Avogadro’s constant 6.02×10²³ mol⁻¹ for particles.
摩尔将质量与粒子数联系起来。n = m/M，M为摩尔质量 (g mol⁻¹)。浓度 c = n/V（体积以 dm³ 计）。在常温常压下，1 mol 气体占据 24 dm³。使用阿伏伽德罗常数 6.02×10²³ mol⁻¹ 计算粒子数。
Percentage yield = (actual yield ÷ theoretical yield) × 100%. Atom economy = (mass of desired product ÷ total mass of reactants) × 100%. Both are frequently tested in IB Stoichiometry and AQA Chemistry calculations.
百分产率 = (实际产量 ÷ 理论产量) × 100%。原子经济性 = (目标产物质量 ÷ 反应物总质量) × 100%。两者在IB化学计量学和AQA化学计算中频繁考查。
11. Exam Technique – Maximising Marks Under Pressure | 考试技巧 – 在紧张中拿分最大化
Read the stem carefully; command words matter: ‘state’ requires a short answer, ‘describe’ needs a step‑by‑step account, ‘explain’ demands a scientific reason. In IB data‑based questions, quote values from the graph. For AQA, the marks in brackets indicate the number of points to make.
仔细阅读题干；指令词很重要：“state”需要简短答案，“describe”要求逐步叙述，“explain”需要给出科学原因。在IB的数据分析题中，引用图表中的具体数值。对于AQA，括号中的分数就暗示了需要写出的要点数量。
Manage your time: if you get stuck, move on and return later. Show all working clearly, especially in multi‑step calculations; a carried‑forward error can still earn marks. Use black pen and draw graphs with a sharp pencil.
管理好时间：如果卡住，先跳过，之后回头再做。清晰展示所有运算步骤，尤其是在多步计算中；延续性的错误仍然可能得分。用黑色水笔书写，用削好的铅笔画图。
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