📚 Pre-U AQA Science: Core Knowledge Summary | Pre-U AQA 科学：核心知识点梳理
The Pre-U AQA Science pathway builds a solid foundation for university-level study by integrating the core concepts of Physics, Chemistry and Biology. This article provides a structured summary of essential knowledge across these disciplines, highlighting key definitions, equations, and mechanisms that students must master for examination success and beyond.
Pre-U AQA 科学课程通过整合物理、化学和生物的核心概念，为大学阶段的学习打下坚实基础。本文系统梳理了这些学科的关键知识，重点阐述了学生为应对考试以及长远发展所必须掌握的定义、方程和反应机制。
1. Mechanics: Kinematics and Newton’s Laws | 力学：运动学与牛顿定律
Kinematics describes motion using quantities such as displacement, velocity, and acceleration. For uniformly accelerated motion along a straight line, the SUVAT equations are used: v = u + at, s = ut + ½at², s = ½(u + v)t, v² = u² + 2as, where u is initial velocity, v is final velocity, a is acceleration, t is time, and s is displacement.
运动学使用位移、速度和加速度等物理量描述运动。对于匀加速直线运动，常用 SUVAT 方程：v = u + at, s = ut + ½at², s = ½(u + v)t, v² = u² + 2as，其中 u 为初速度，v 为末速度，a 为加速度，t 为时间，s 为位移。
Newton’s first law states that an object remains at rest or in uniform motion unless acted upon by a resultant force. The second law quantifies this relationship: F = ma, where force is measured in newtons (N), mass in kg, and acceleration in m s⁻². The third law explains that if body A exerts a force on body B, then B exerts an equal and opposite force on A.
牛顿第一定律指出，物体将保持静止或匀速直线运动状态，除非受到合外力的作用。第二定律量化了这一关系：F = ma，力的单位是牛顿 (N)，质量单位为 kg，加速度单位为 m s⁻²。第三定律说明，若物体 A 对物体 B 施加一个力，则 B 同时对 A 施加一个大小相等、方向相反的力。
Momentum p is defined as p = mv. The principle of conservation of momentum states that in a closed system, total momentum before a collision equals total momentum after, provided no external forces act. Impulse is the product of force and time, equal to the change in momentum: FΔt = Δp.
动量 p 定义为 p = mv。动量守恒定律指出，在不受外力的封闭系统中，碰撞前的总动量等于碰撞后的总动量。冲量是力与时间的乘积，等于动量的变化量：FΔt = Δp。
2. Electricity: Circuits and Ohm’s Law | 电学：电路与欧姆定律
Electric current I is the rate of flow of charge: I = ΔQ/Δt. Potential difference V is the energy transferred per unit charge: V = W/Q. Resistance R is defined by R = V/I, and Ohm’s law applies to ohmic conductors where the ratio V/I is constant at constant temperature.
电流 I 是电荷流动的速率：I = ΔQ/Δt。电势差 V 是单位电荷转移的能量：V = W/Q。电阻 R 定义为 R = V/I，欧姆定律适用于欧姆导体，即在温度恒定时 V/I 的比值为常数。
Resistors in series carry the same current; the total resistance Rₜ = R₁ + R₂ + R₃ + … . In parallel, the potential difference across each branch is the same, and total resistance is given by 1/Rₜ = 1/R₁ + 1/R₂ + … . Power dissipated in a component is P = IV = I²R = V²/R.
串联电阻器通过的电流相同；总电阻 Rₜ = R₁ + R₂ + R₃ + … 。并联时，各支路两端电势差相等，总电阻满足 1/Rₜ = 1/R₁ + 1/R₂ + … 。元件消耗的功率为 P = IV = I²R = V²/R。
Electromotive force (emf) ε of a source is the energy supplied per unit charge. The terminal potential difference V is given by V = ε − Ir, where r is the internal resistance. Kirchhoff’s laws govern complex circuits: the junction rule states ΣI_in = ΣI_out, and the loop rule states Σε = ΣIR around any closed loop.
电源的电动势 ε 是单位电荷提供的能量。端电压 V 由 V = ε − Ir 给出，其中 r 为内阻。基尔霍夫定律适用于复杂电路：节点电流定律指出 ΣI_入 = ΣI_出，环路电压定律指出沿任意闭合回路 Σε = ΣIR。
3. Waves: Properties and Electromagnetic Spectrum | 波动：性质与电磁波谱
A progressive wave transfers energy without net transfer of matter. The wave equation links speed v, frequency f, and wavelength λ: v = fλ. Transverse waves have oscillations perpendicular to the direction of energy transfer (e.g., light, water waves), while longitudinal waves oscillate parallel to that direction (e.g., sound).
行波传递能量而不发生物质的净转移。波动方程关联波速 v、频率 f 和波长 λ：v = fλ。横波的振动方向与能量传播方向垂直（如光波、水波），而纵波的振动方向与传播方向平行（如声波）。
Superposition occurs when two or more waves meet; the resultant displacement is the vector sum of individual displacements. Stationary waves form when two identical progressive waves travel in opposite directions, creating nodes (zero displacement) and antinodes (maximum amplitude). The distance between adjacent nodes is λ/2.
两列或更多波相遇时发生叠加，合位移等于各波位移的矢量和。两列相同的行波沿相反方向传播时形成驻波，产生波节（位移为零）和波腹（振幅最大）。相邻波节间距为 λ/2。
The electromagnetic spectrum, in order of increasing frequency and decreasing wavelength, includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. All travel at speed c = 3.00 × 10⁸ m s⁻¹ in a vacuum.
电磁波谱按频率递增、波长递减的顺序，包括无线电波、微波、红外线、可见光、紫外线、X 射线和 γ 射线。所有电磁波在真空中以速率 c = 3.00 × 10⁸ m s⁻¹ 传播。
4. Atomic Structure and Radioactivity | 原子结构与放射性
The nuclear model of the atom describes a small, dense nucleus containing protons and neutrons, surrounded by electrons in discrete energy levels. The atomic number Z equals the number of protons; the mass number A = Z + N, where N is the neutron number. Isotopes share the same Z but different N.
原子的核式模型描述了一个由质子和中子构成的致密原子核，以及核外分层排布的电子。原子序数 Z 等于质子数；质量数 A = Z + N，N 为中子数。同位素具有相同的 Z 但不同的 N。
Radioactive decay occurs when an unstable nucleus emits radiation. Alpha (α) particles are helium nuclei (⁴₂He), beta (β⁻) are electrons emitted when a neutron transforms to a proton, and gamma (γ) rays are high-frequency electromagnetic waves. The decay is governed by the exponential law: N = N₀ e⁻λt, with half-life T₁/₂ = ln 2/λ.
不稳定的原子核发射辐射时发生放射性衰变。α 粒子是氦核 (⁴₂He)，β⁻ 粒子是中子转变为质子时发射的电子，γ 射线是高频电磁波。衰变遵循指数规律：N = N₀ e⁻λt，半衰期 T₁/₂ = ln 2/λ。
The activity A of a sample is the number of decays per unit time, measured in becquerels (Bq). Background radiation originates from natural sources (cosmic rays, rocks) and artificial sources. Nuclear fission and fusion release energy due to a mass defect, expressed by E = mc².
样品的放射性活度 A 为单位时间内的衰变次数，单位为贝克勒尔 (Bq)。本底辐射来源于天然源（宇宙射线、岩石）和人工源。核裂变与核聚变由于质量亏损而释放能量，由 E = mc² 表示。
5. Chemical Bonding and Structure | 化学键与结构
Ionic bonding involves the electrostatic attraction between oppositely charged ions formed by electron transfer. Metals lose electrons to form cations, non-metals gain electrons to form anions. Ionic compounds have giant lattice structures, high melting points, and conduct electricity when molten or dissolved.
离子键是通过电子转移形成相反电荷离子之间的静电吸引。金属失去电子形成阳离子，非金属得到电子形成阴离子。离子化合物具有巨型晶格结构，熔点高，在熔融或溶解时能导电。
Covalent bonding is the sharing of electron pairs between atoms, forming molecules or giant covalent structures (e.g., diamond, SiO₂). The shape of a molecule is predicted by VSEPR theory: for example, CH₄ is tetrahedral (bond angle 109.5°), NH₃ is trigonal pyramidal (107°), and H₂O is bent (104.5°).
共价键是原子间通过共用电子对形成的，可构成分子或巨型共价结构（如金刚石、SiO₂）。分子的形状通过 VSEPR 理论预测：例如，CH₄ 为四面体形（键角 109.5°），NH₃ 为三角锥形（107°），H₂O 为 V 形（104.5°）。
Metallic bonding arises from the attraction between a lattice of positive metal ions and a ‘sea’ of delocalised electrons. This model explains electrical conductivity, malleability, and ductility. Electronegativity increases across a period and decreases down a group, influencing bond polarity.
金属键产生于金属阳离子晶格与离域电子“海洋”之间的吸引作用。该模型解释了导电性、延展性和可塑性。电负性沿周期递增、沿族递减，影响键的极性。
6. Energetics and Reaction Kinetics | 能量学与反应动力学
Enthalpy change ΔH is the heat energy transferred at constant pressure. Exothermic reactions release energy (ΔH negative), while endothermic reactions absorb energy. Standard enthalpy of formation ΔH_f° refers to the formation of 1 mole of compound from its elements under standard conditions.
焓变 ΔH 为恒压条件下传递的热能。放热反应释放能量（ΔH 为负），吸热反应吸收能量。标准生成焓 ΔH_f° 是指在标准条件下，由元素生成 1 mol 化合物时的焓变。
Hess’s law states that the total enthalpy change for a reaction is independent of the route taken. Bond enthalpies can estimate ΔH as: ΔH = Σ (bonds broken) − Σ (bonds formed). Calorimetry experiments use q = mcΔT to measure heat change, where c is specific heat capacity.
赫斯定律指出，一个反应的总焓变与反应途径无关。键焓可用于估算 ΔH：ΔH = Σ (断键能量) − Σ (成键能量)。量热实验利用 q = mcΔT 测量热量变化，其中 c 为比热容。
The rate of reaction is affected by concentration, temperature, surface area, and catalysts. The Maxwell-Boltzmann distribution shows that only particles with energy above the activation energy Eₐ can react. Catalysts provide an alternative pathway with lower Eₐ, increasing the proportion of successful collisions.
反应速率受浓度、温度、表面积和催化剂的影响。麦克斯韦-玻尔兹曼分布表明，只有能量高于活化能 Eₐ 的粒子才能反应。催化剂提供了具有较低 Eₐ 的替代路径，从而增加有效碰撞的比例。
7. Organic Chemistry: Functional Groups and Reactions | 有机化学：官能团与反应
Hydrocarbons are classified as alkanes (single bonds, general formula CₙH₂ₙ₊₂) and alkenes (contain a C=C double bond, CₙH₂ₙ). Alkanes undergo combustion and free-radical substitution with halogens. Alkenes undergo electrophilic addition, such as with HBr or Br₂, following Markovnikov’s rule where appropriate.
碳氢化合物分为烷烃（单键，通式 CₙH₂ₙ₊₂）和烯烃（含 C=C 双键，通式 CₙH₂ₙ）。烷烃可发生燃烧以及与卤素的自由基取代反应。烯烃可发生亲电加成，如与 HBr 或 Br₂ 反应，在适用情况下遵循马氏规则。
Key functional groups include alcohols (–OH), haloalkanes (–X), aldehydes (–CHO), ketones (>C=O), carboxylic acids (–COOH), esters (–COO–), amines (–NH₂) and amides (–CONH₂). Oxidation of primary alcohols yields aldehydes then carboxylic acids; secondary alcohols give ketones.
关键官能团包括醇 (–OH)、卤代烷 (–X)、醛 (–CHO)、酮 (>C=O)、羧酸 (–COOH)、酯 (–COO–)、胺 (–NH₂) 和酰胺 (–CONH₂)。伯醇氧化先得到醛再得到羧酸；仲醇氧化得到酮。
Polymers are large molecules formed from repeating monomer units. Addition polymers such as poly(ethene) form from alkenes, while condensation polymers like polyesters and polyamides form with elimination of a small molecule such as water. Biopolymers include proteins (polyamides) and DNA (polynucleotides).
聚合物是由重复单体单元构成的大分子。加聚物如聚乙烯由烯烃形成；缩聚物如聚酯和聚酰胺在形成时脱去小分子（如水）。生物聚合物包括蛋白质（聚酰胺）和 DNA（多核苷酸）。
8. Cells and Biological Molecules | 细胞与生物分子
The cell is the basic unit of life. Eukaryotic cells possess a membrane-bound nucleus and organelles such as mitochondria, ribosomes, and endoplasmic reticulum. Prokaryotic cells lack a nucleus and membrane-bound organelles. The fluid mosaic model describes the cell membrane as a phospholipid bilayer with embedded proteins.
细胞是生命的基本单位。真核细胞具有膜包被的细胞核以及线粒体、核糖体和内质网等细胞器。原核细胞没有细胞核和膜包被的细胞器。流动镶嵌模型将细胞膜描述为一侧带有嵌入蛋白的磷脂双分子层。
Key biological molecules include carbohydrates (monosaccharides like glucose, formula C₆H₁₂O₆, disaccharides like sucrose, and polysaccharides like starch, glycogen, cellulose), lipids (triglycerides composed of glycerol and three fatty acids), and proteins (polymers of amino acids with four structural levels).
关键生物分子包括碳水化合物（单糖如葡萄糖，分子式 C₆H₁₂O₆；二糖如蔗糖；以及多糖如淀粉、糖原、纤维素）、脂类（由甘油和三个脂肪酸组成的甘油三酯）和蛋白质（具有四级结构的氨基酸聚合物）。
Nucleic acids DNA and RNA are polymers of nucleotides. DNA contains the bases adenine, thymine, cytosine, and guanine, with a double helix held by hydrogen bonds and complementary base pairing (A–T, C–G). RNA replaces thymine with uracil and is generally single-stranded. ATP (adenosine triphosphate) is the immediate energy currency of cells.
核酸 DNA 和 RNA 是核苷酸的聚合物。DNA 含有腺嘌呤、胸腺嘧啶、胞嘧啶和鸟嘌呤四种碱基，形成由氢键和互补碱基对（A–T, C–G）维持的双螺旋结构。RNA 以尿嘧啶替代胸腺嘧啶，一般为单链。ATP（三磷酸腺苷）是细胞的直接能量货币。
9. Cell Division and Genetics | 细胞分裂与遗传学
Mitosis produces two genetically identical diploid daughter cells, essential for growth and repair. Its stages are prophase, metaphase, anaphase, and telophase, followed by cytokinesis. Meiosis produces four haploid gametes, introducing genetic variation through independent assortment and crossing over.
有丝分裂产生两个遗传上完全相同的二倍体子细胞，对于生长和修复至关重要。其阶段依次为前期、中期、后期和末期，随后进行胞质分裂。减数分裂产生四个单倍体配子，通过独立分配和交叉互换引入遗传变异。
Genes are segments of DNA that code for polypeptides. Alleles are different versions of a gene. Monohybrid inheritance follows Mendel’s laws: the 3:1 phenotypic ratio in the F₂ generation for a dominant trait. Co-dominance and multiple alleles (e.g., ABO blood group) exhibit different patterns.
基因是编码多肽的 DNA 片段。等位基因是同一基因的不同形式。单基因遗传遵循孟德尔定律：对于显性性状，F₂ 代表型比为 3:1。共显性和复等位基因（如 ABO 血型）表现出不同的模式。
Sex linkage occurs when a gene is located on a sex chromosome, often the X chromosome. Examples include haemophilia and red-green colour blindness. Pedigree analysis can trace inheritance patterns across generations.
当基因位于性染色体（通常是 X 染色体）上时，为性连锁遗传。例如血友病和红绿色盲。系谱分析可追踪世代间的遗传模式。
10. Ecology and Energy Transfer | 生态学与能量传递
An ecosystem comprises a community of living organisms interacting with their abiotic environment. Energy enters via photosynthesis: light energy is converted to chemical energy in glucose: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Energy flows through food chains but is lost at each trophic level as heat.
生态系统由生物群落及其与非生物环境的相互作用构成。能量通过光合作用进入：光能转化为葡萄糖中的化学能：6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂。能量沿食物链流动，但在每个营养级都会以热的形式损失。
Biomass can be measured as dry mass. The efficiency of energy transfer between trophic levels is calculated as (energy available after transfer / energy available before transfer) × 100%, typically around 10%. Pyramids of energy, biomass, and numbers illustrate ecological structure.
生物量可以干重来衡量。营养级之间能量传递效率的计算公式为（传递后可利用的能量 / 传递前可利用的能量）× 100%，通常约为 10%。能量塔、生物量塔和数量塔可说明生态结构。
The carbon cycle involves the movement of carbon among the atmosphere, oceans, and living organisms through processes such as photosynthesis, respiration, combustion, and decomposition. The nitrogen cycle includes nitrogen fixation, nitrification, assimilation, ammonification, and denitrification, driven by microorganisms.
碳循环涉及碳在大气、海洋和生物体之间的移动，通过光合作用、呼吸作用、燃烧和分解等过程实现。氮循环包括固氮作用、硝化作用、同化作用、氨化作用和反硝化作用，由微生物驱动。
11. Homeostasis and Response | 稳态与响应
Homeostasis is the maintenance of a constant internal environment. Negative feedback mechanisms regulate factors like blood glucose, temperature, and water potential. The pancreas detects blood glucose changes and secretes insulin (to lower glucose) or glucagon (to raise it), acting on liver cells.
稳态是维持恒定内环境的能力。负反馈机制调节血糖、体温和水势等因素。胰腺检测血糖变化，并分泌胰岛素（降低血糖）或胰高血糖素（升高血糖），作用于肝细胞。
The nervous system uses electrical impulses transmitted by neurones. A reflex arc consists of a receptor, sensory neurone, relay neurone, motor neurone, and effector, enabling rapid, automatic responses. Synapses use neurotransmitters to cross the gap between neurones.
神经系统利用神经元传导的电脉冲。反射弧由感受器、感觉神经元、中继神经元、运动神经元和效应器组成，可实现快速自动反应。突触利用神经递质跨过神经元之间的间隙。
Hormonal coordination is slower but longer-lasting than nervous control. For instance, adrenaline prepares the body for ‘fight or flight’ by increasing heart rate and glucose availability. The kidneys control water balance via ADH, which adjusts the permeability of collecting ducts.
激素协调作用比神经控制缓慢，但持续时间更长。例如，肾上腺素通过提高心率和葡萄糖可用性，让机体为“战斗或逃跑”做好准备。肾脏通过抗利尿激素 ADH 调节集合管通透性，控制水平衡。
12. Scientific Skills and Practical Applications | 科学技能与实践应用
Across all three sciences, core practical skills are assessed. Students must be able to design investigations, identify variables (independent, dependent, control), present data in tables and graphs, and analyse results. Accuracy, precision, repeatability, and reproducibility are key terms in evaluation.
在三门科学中，核心实验技能均被考核。学生须能设计探究方案、识别变量（自变量、因变量、控制变量）、以表格和图表呈现数据，并分析结果。准确度、精密度、可重复性和再现性是评价的关键术语。
Uncertainty in measurements is recorded as ± the smallest scale division or calculated from the range of repeats. Percentage error is useful for comparing uncertainties. Drawing lines of best fit, calculating gradients, and using rate = change in quantity / time are essential quantitative skills.
测量中的不确定度记录为 ± 最小刻度值，或由重复测量极差计算得出。百分误差有助于比较不确定度。绘制最佳拟合线、计算梯度，以及运用速率 = 量的变化 / 时间的技能，都是必备的定量技能。
Risk assessments and ethical considerations (especially in biology) are integrated throughout. Students learn to use appropriate units, convert between SI prefixes (nano, micro, milli, centi, kilo, mega), and express results using standard form and significant figures.
风险评估和伦理考量（尤其在生物学中）贯穿始终。学生学习使用恰当的单位，转换 SI 词头（纳、微、毫、厘、千、兆），并用标准形式和有效数字表达结果。
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