Year 12 WJEC Science: Core Knowledge Summary | WJEC Year 12 科学：核心知识点梳理

📚 Year 12 WJEC Science: Core Knowledge Summary | WJEC Year 12 科学：核心知识点梳理

For Year 12 students following the WJEC AS Science specification, mastering the core ideas across biology, chemistry and physics is the foundation for exam success. This article distils the key knowledge areas, linking concepts and highlighting the skills needed to analyse, evaluate and apply scientific principles. Use this summary alongside your practical work to build a confident understanding of the fundamental topics.

对于学习WJEC AS 科学课程的 Year 12 学生来说，掌握生物、化学和物理的核心概念是考试成功的基础。本文提炼了关键知识领域，串联各个概念，并突出分析、评估和应用科学原理所需的技能。请结合你的实验操作使用这份总结，建立对基本主题的坚实理解。

---

1. Cell Structure & Function | 细胞结构与功能

The cell is the basic unit of life. Eukaryotic cells (animals, plants, fungi) contain membrane-bound organelles, including the nucleus, mitochondria, ribosomes and, in plant cells, chloroplasts and a permanent vacuole. Prokaryotic cells (bacteria) lack a nucleus and have their DNA free in the cytoplasm as a single circular chromosome, often accompanied by plasmids. The fluid-mosaic model describes the cell membrane as a phospholipid bilayer with embedded proteins, cholesterol and glycoproteins, controlling the movement of substances via diffusion, facilitated diffusion, osmosis and active transport.

细胞是生命的基本单位。真核细胞（动物、植物、真菌）含有膜包被的细胞器，包括细胞核、线粒体、核糖体，植物细胞还有叶绿体和永久液泡。原核细胞（细菌）没有细胞核，其 DNA 以一条环状染色体的形式游离在细胞质中，通常还带有质粒。流动镶嵌模型将细胞膜描述为磷脂双分子层，其中嵌有蛋白质、胆固醇和糖蛋白，通过扩散、易化扩散、渗透和主动运输控制物质的进出。

• Eukaryotic vs Prokaryotic: Membrane-bound organelles present vs absent. | 真核与原核：膜包被细胞器有 vs 无。
• Organelle functions: Mitochondrion – aerobic respiration; chloroplast – photosynthesis; ribosome – protein synthesis. | 细胞器功能：线粒体—有氧呼吸；叶绿体—光合作用；核糖体—蛋白质合成。
• Membrane transport: Passive (diffusion, osmosis) does not require ATP; active transport and endocytosis require energy. | 膜运输：被动（扩散、渗透）不需要 ATP；主动运输和内吞作用需要能量。

---

2. Biological Molecules | 生物大分子

Living organisms are built from carbon-based macromolecules. Carbohydrates include monosaccharides (e.g. glucose, C₆H₁₂O₆), disaccharides (e.g. sucrose) and polysaccharides (starch, glycogen, cellulose). Lipids are composed of glycerol and fatty acids; triglycerides serve as energy stores, while phospholipids form membranes. Proteins are polymers of amino acids, folded into specific three-dimensional shapes determined by their primary sequence; the levels of structure (primary, secondary, tertiary, quaternary) are stabilised by hydrogen bonds, ionic bonds, disulfide bridges and hydrophobic interactions. Nucleic acids DNA and RNA carry genetic information using a sugar-phosphate backbone and nitrogenous bases.

生物体由碳基大分子构成。碳水化合物包括单糖（例如葡萄糖，C₆H₁₂O₆）、二糖（例如蔗糖）和多糖（淀粉、糖原、纤维素）。脂类由甘油和脂肪酸组成；甘油三酯作为能量储存，而磷脂形成细胞膜。蛋白质是氨基酸的多聚体，折叠成由一级序列决定的特定三维形状；四级结构层次（一级、二级、三级、四级）由氢键、离子键、二硫桥和疏水相互作用稳定。核酸 DNA 和 RNA 通过糖-磷酸骨架和含氮碱基携带遗传信息。

Molecule	Monomer	Bond	Example
Carbohydrate | 碳水化合物	Monosaccharide | 单糖	Glycosidic | 糖苷键	Starch | 淀粉
Protein | 蛋白质	Amino acid | 氨基酸	Peptide | 肽键	Haemoglobin | 血红蛋白
Nucleic acid | 核酸	Nucleotide | 核苷酸	Phosphodiester | 磷酸二酯键	DNA | DNA

---

3. Atomic Structure & Periodicity | 原子结构与周期性

Atoms consist of protons (+1 charge), neutrons (0) and electrons (–1). The atomic number Z equals the number of protons; the mass number A = protons + neutrons. Electrons occupy shells and subshells (s, p, d, f) according to the Aufbau principle, Hund’s rule and the Pauli exclusion principle. The periodic table arranges elements in order of increasing atomic number, with periods corresponding to the highest occupied principal quantum number and groups sharing the same valence electron configuration. Trends across periods and down groups include atomic radius, ionisation energy and electronegativity.

原子由质子（+1 电荷）、中子（0）和电子（–1）组成。原子序数 Z 等于质子数；质量数 A = 质子数 + 中子数。电子根据构造原理、洪特规则和泡利不相容原理填充壳层和亚层（s、p、d、f）。元素周期表按原子序数递增排列元素，周期对应于最高占据主量子数，族共享相同的价电子排布。周期和族的递变规律包括原子半径、电离能和电负性。

• First ionisation energy: X(g) → X⁺(g) + e⁻; increases across a period, decreases down a group. | 第一电离能：X(气) → X⁺(气) + e⁻；同周期从左到右增大，同族从上到下减小。
• Electron configuration notation: e.g. Na: 1s² 2s² 2p⁶ 3s¹ or [Ne] 3s¹. | 电子排布表示法：例如 Na: 1s² 2s² 2p⁶ 3s¹ 或 [Ne] 3s¹。

---

4. Chemical Bonding & Molecular Shape | 化学键与分子形状

Ionic bonding involves electron transfer between metal and non-metal atoms, forming a giant ionic lattice held by electrostatic attraction. Covalent bonding occurs when atoms share electron pairs; bond polarity arises from differences in electronegativity. Metallic bonding describes a lattice of positive ions in a ‘sea’ of delocalised electrons. The shapes of molecules and polyatomic ions can be predicted using VSEPR theory (valence shell electron pair repulsion). Common shapes include linear (e.g. BeCl₂, CO₂), trigonal planar (BF₃), tetrahedral (CH₄, NH₄⁺), pyramidal (NH₃) and bent (H₂O).

离子键涉及金属原子与非金属原子之间的电子转移，形成由静电引力维持的巨型离子晶格。共价键通过原子共享电子对形成；键的极性源自电负性差异。金属键描述的是阳离子在离域电子“海洋”中的晶格。分子和多原子离子的形状可用 VSEPR 理论（价层电子对互斥）预测。常见形状包括直线形（如 BeCl₂、CO₂）、平面三角形（BF₃）、四面体形（CH₄、NH₄⁺）、三角锥形（NH₃）和 V 形（H₂O）。

Bond type	Property	Example
Ionic | 离子键	High m.p., conducts when molten | 高熔点，熔融时导电	NaCl | NaCl
Covalent (simple) | 简单共价	Low m.p., non-conductor | 低熔点，不导电	H₂O | H₂O
Covalent (giant) | 巨型共价	Very high m.p., hard | 极高熔点，坚硬	Diamond | 金刚石
Metallic | 金属键	Malleable, conducts as solid | 延展性好，固态导电	Cu | Cu

---

5. Energetics & Enthalpy Changes | 能量学与焓变

Chemical reactions are accompanied by energy changes, usually measured as enthalpy change ΔH at constant pressure. Exothermic reactions release heat to the surroundings (ΔH negative); endothermic reactions absorb heat (ΔH positive). Standard enthalpy changes are quoted under standard conditions (100 kPa, 298 K). Key definitions include enthalpy of formation (ΔH_f°), combustion (ΔH_c°) and neutralisation (ΔH_neut). Hess’s law states that the enthalpy change for a reaction is independent of the route taken, allowing enthalpy changes to be calculated from other data. Average bond enthalpies can also be used to estimate ΔH of a reaction: ΔH = Σ(bonds broken) – Σ(bonds formed).

化学反应伴随能量变化，通常以恒压下的焓变 ΔH 来衡量。放热反应向周围释放热量（ΔH 为负值）；吸热反应吸收热量（ΔH 为正值）。标准焓变是在标准条件（100 kPa、298 K）下测定的。关键定义包括生成焓（ΔH_f°）、燃烧焓（ΔH_c°）和中和焓（ΔH_neut）。赫斯定律指出，一个反应的焓变与途径无关，因此可以利用其它数据计算焓变。平均键焓也可用于估算反应 ΔH：ΔH = Σ(断裂键的键焓) – Σ(形成键的键焓)。

ΔH = ΣΔH_f°(products) – ΣΔH_f°(reactants)

q = mcΔT (for calorimetry)

---

6. Kinetics & Equilibria | 反应动力学与平衡

Reaction kinetics studies the rate of chemical reactions and the factors that affect it. The collision theory states that particles must collide with sufficient energy (greater than or equal to the activation energy Eₐ) and with the correct orientation for a reaction to occur. The Maxwell-Boltzmann distribution shows the spread of molecular energies in a gas at a given temperature; increasing temperature shifts the curve to the right, increasing the proportion of particles with energy ≥ Eₐ. Catalysts provide an alternative pathway with lower Eₐ, increasing reaction rate without being consumed. For reversible reactions, dynamic equilibrium is reached when the rates of forward and reverse reactions are equal. Le Chatelier’s principle predicts how an equilibrium shifts in response to changes in concentration, pressure and temperature.

反应动力学研究化学反应速率及其影响因素。碰撞理论指出，粒子必须以足够的能量（大于或等于活化能 Eₐ）和正确的取向碰撞，反应才会发生。麦克斯韦-玻尔兹曼分布展示了给定温度下气体分子能量的分布情况；升高温度使曲线向右移动，增加能量 ≥ Eₐ 的分子比例。催化剂提供一条活化能较低的替代路径，从而提高反应速率而不被消耗。对于可逆反应，当正逆反应速率相等时达到动态平衡。勒夏特列原理可预测平衡如何因浓度、压力和温度的变化而移动。

• Factors affecting rate: temperature, concentration/pressure, surface area, catalyst. | 影响速率的因素：温度、浓度/压力、表面积、催化剂。
• Equilibrium constant K_c: For aA + bB ⇌ cC + dD, K_c = [C]^c [D]^d / [A]^a [B]^b. | 平衡常数 K_c：对反应 aA + bB ⇌ cC + dD，K_c = [C]^c [D]^d / [A]^a [B]^b。

---

7. Mechanics: Motion & Forces | 力学：运动与力

Kinematics describes the motion of objects using quantities such as displacement (s), velocity (v), acceleration (a) and time (t). The SUVAT equations apply for uniform acceleration in a straight line. Newton’s laws of motion form the foundation of dynamics: first law (inertia), second law (F = ma) and third law (action-reaction pairs). Momentum p = mv is conserved in collisions, provided no external resultant force acts. Impulse (FΔt) equals the change in momentum. Free-body diagrams help analyse forces acting on an object; the resultant force determines the acceleration. Frictional forces oppose motion and can be modelled using coefficients of friction.

运动学使用位移（s）、速度（v）、加速度（a）和时间（t）等量描述物体的运动。在匀加速直线运动中可运用 SUVAT 方程。牛顿运动定律是动力学的基础：第一定律（惯性）、第二定律（F = ma）和第三定律（作用力与反作用力）。在没有合外力作用时，动量 p = mv 在碰撞中守恒。冲量（FΔt）等于动量的变化量。受力分析图有助于分析作用在物体上的力；合力决定加速度。摩擦力阻碍运动，可用摩擦系数进行建模。

SUVAT: v = u + at; s = ut + ½at²; v² = u² + 2as; s = ½(u+v)t

Quantity | 量	Symbol	Scalar / Vector
Displacement | 位移	s	Vector | 矢量
Speed | 速率	u, v	Scalar | 标量
Acceleration | 加速度	a	Vector | 矢量

---

8. Waves & Optics | 波动与光学

Waves transfer energy without transferring matter. Transverse waves (e.g. light, water waves) have oscillations perpendicular to the direction of energy transfer; longitudinal waves (e.g. sound) have oscillations parallel to it. Key wave properties include amplitude (A), wavelength (λ), frequency (f) and wave speed (v = fλ). The principle of superposition leads to interference: constructive interference occurs when waves meet in phase, destructive when out of phase. Standing waves form on strings and in pipes, with nodes and antinodes at fixed positions. Electromagnetic waves travel at speed c in a vacuum and exhibit reflection, refraction (Snell’s law: n₁ sin θ₁ = n₂ sin θ₂), diffraction and polarisation.

波传递能量而不传递物质。横波（如光波、水波）的振动方向与能量传递方向垂直；纵波（如声波）的振动方向则与之平行。波的关键属性包括振幅（A）、波长（λ）、频率（f）和波速（v = fλ）。叠加原理导致干涉现象：当波在相同相位相遇时发生相长干涉，反相位时发生相消干涉。弦和管内可形成驻波，其节点和反节点位置固定。电磁波在真空中以光速 c 传播，并表现出反射、折射（斯涅尔定律：n₁ sin θ₁ = n₂ sin θ₂）、衍射和偏振等现象。

• Refractive index: n = c/v; determines how much light bends. | 折射率：n = c/v；决定光线的弯曲程度。
• Total internal reflection: occurs when light travels from a denser to a less dense medium at an incident angle greater than the critical angle. | 全内反射：光从光密介质射向光疏介质，且入射角大于临界角时发生。

---

9. Electricity & Circuits | 电学与电路

Electric current (I) is the rate of flow of charge; charge is measured in coulombs (Q = It). Potential difference (V) is the energy transferred per unit charge. Resistance (R = V/I) opposes current; Ohm’s law states that V ∝ I for an ohmic conductor at constant temperature. Resistivity ρ is an intrinsic property of a material: R = ρL/A, where L is length and A is cross-sectional area. Circuits follow Kirchhoff’s laws: the sum of currents entering a junction equals the sum leaving; the sum of e.m.f.s equals the sum of potential differences around a closed loop. Components in series share the same current; in parallel they share the same voltage. Power P = IV = I²R = V²/R.

电流（I）是电荷流动的速率；电荷的单位是库仑（Q = It）。电势差（V）是单位电荷传递的能量。电阻（R = V/I）阻碍电流；欧姆定律指出，在恒温下，欧姆导体的 V ∝ I。电阻率 ρ 是材料的本征属性：R = ρL/A，其中 L 为长度，A 为横截面积。电路遵循基尔霍夫定律：流入节点的电流之和等于流出电流之和；沿闭合回路，电动势之和等于电势差之和。串联元件电流相同；并联元件电压相同。功率 P = IV = I²R = V²/R。

Circuit Component	Behaviour	I-V graph
Ohmic conductor | 欧姆导体	Straight line through origin | 过原点的直线	Linear | 线性
Filament lamp | 白炽灯	Resistance increases with temp | 电阻随温度升高	Curve (flattens at high V) | 曲线（高 V 区平坦）
Diode | 二极管	Forward biased – very low R; reverse – very high R | 正向偏压低电阻；反向极高电阻	Sharp rise after threshold | 阈值后急剧上升

---

10. Practical Skills & Data Analysis | 实验技能与数据分析

Practical work is integral to WJEC AS Science. Students must be able to design investigations, identify independent, dependent and control variables, and assess risks. Accurate measurements involve careful use of instruments (e.g. micrometer, volumetric pipette, multimeter) and appropriate units. Uncertainties are expressed as absolute (±) or percentage uncertainty. Repeating readings improves reliability; identifying anomalies is part of evaluation. Graphs should be plotted with labelled axes, sensible scales and line of best fit. Gradient and intercept calculations provide valuable information (e.g. activation energy from an Arrhenius plot, Young’s modulus from a stress–strain graph).

实验操作是 WJEC AS 科学的重要组成部分。学生必须能够设计探究活动，识别自变量、因变量和控制变量，并评估风险。精确测量需要谨慎使用仪器（如千分尺、移液管、万用表）和合适的单位。不确定度以绝对不确定度（±）或百分比不确定度表示。重复读数可以提高可靠性；识别异常值是评价的一部分。作图应标注轴标签、合理刻度和最佳拟合线。斜率和截距的计算能提供有价值的信息（例如从阿伦尼乌斯图获得活化能，从应力-应变图获得杨氏模量）。

• Significant figures: Final answers should reflect the precision of the data (usually 2–3 s.f.). | 有效数字：最终答案应反映数据的精确度（通常 2–3 位有效数字）。
• Error bars: Used to show uncertainty on graphs; overlapping bars suggest differences may not be significant. | 误差线：在图中显示不确定度；相互重叠暗示差异可能不显著。
• Evaluating methods: Comment on accuracy, precision, repeatability and sources of systematic/random error. | 方法评估：评价准确度、精密度、可重复性以及系统/随机误差的来源。

---

Published by TutorHao | Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）