📚 AS CIE Science: Core Knowledge Review | AS CIE 科学：核心知识点梳理
This article consolidates the essential topics across AS Level Physics, Chemistry, and Biology for the CIE syllabus. Mastering these core concepts builds a strong foundation for examinations and further study.
本文梳理了CIE AS阶段物理、化学和生物的核心知识点。掌握这些基础概念有助于备考和后续学习。
1. Kinematics and Dynamics | 运动学与动力学
Kinematics describes motion using displacement, velocity, and acceleration. For uniformly accelerated linear motion, the SUVAT equations (v = u + at, s = ut + ½at², v² = u² + 2as, and s = (u+v)t/2) are essential tools.
运动学用位移、速度和加速度描述运动。对于匀加速直线运动，SUVAT方程（v = u + at, s = ut + ½at², v² = u² + 2as, s = (u+v)t/2）是基本工具。
Dynamics relates forces to motion via Newton’s laws. The first law defines inertia; the second law states net force F = ma; the third law expresses action–reaction pairs. Momentum p = mv is conserved in isolated systems and is linked to impulse (FΔt = Δp).
动力学通过牛顿定律将力与运动联系起来。第一定律定义惯性；第二定律指出净力F = ma；第三定律表示作用力与反作用力。动量p = mv在孤立系统中守恒，并与冲量(FΔt = Δp)相关。
Projectile motion is analysed by resolving initial velocity into horizontal and vertical components. The horizontal component gives constant velocity, while the vertical motion experiences uniform acceleration g ≈ 9.81 m s⁻².
抛体运动可通过分解初速度为水平和竖直分量来分析。水平方向为匀速，竖直方向受重力加速度g ≈ 9.81 m s⁻²匀加速。
2. Waves and Optics | 波与光学
Waves transfer energy without net matter transfer. The wave equation v = fλ links speed, frequency, and wavelength. Transverse waves (e.g., light) vibrate perpendicular to propagation; longitudinal waves (e.g., sound) vibrate parallel.
波动传递能量而不传递物质。波速方程v = fλ联系波速、频率和波长。横波（如光）振动方向垂直于传播方向；纵波（如声）振动方向平行于传播方向。
Superposition of waves causes constructive or destructive interference. Stationary waves formed by reflection show nodes and antinodes. Young’s double‑slit experiment demonstrates light interference and measures wavelength.
波的叠加产生相长或相消干涉。反射形成的驻波呈现波节和波腹。杨氏双缝实验演示光的干涉并可测量波长。
Refraction follows Snell’s law: n₁ sin θ₁ = n₂ sin θ₂. Total internal reflection occurs when light passes from a denser to a rarer medium at an angle greater than the critical angle, a principle used in optical fibres.
折射遵循斯涅耳定律：n₁ sin θ₁ = n₂ sin θ₂。当光从光密介质射向光疏介质且入射角大于临界角时发生全内反射，该原理用于光纤。
3. Electricity and Circuits | 电学与电路
Current I = ΔQ/Δt is the rate of charge flow. Ohm’s law V = IR defines resistance R. Resistivity links resistance to material and geometry: R = ρL/A.
电流I = ΔQ/Δt是电荷流动速率。欧姆定律V = IR定义电阻R。电阻率将电阻与材料和几何尺寸关联：R = ρL/A。
In series circuits, current is the same everywhere and total resistance is the sum of individual resistances. In parallel circuits, voltage is the same across branches, and 1/Rₜₒₜₐₗ = 1/R₁ + 1/R₂ + …
串联电路中电流处处相等，总电阻为各电阻之和。并联电路中各支路电压相同，1/Rₜₒₜₐₗ = 1/R₁ + 1/R₂ + …
Kirchhoff’s junction rule (ΣI = 0) and loop rule (ΣV = 0) are used for complex circuits. A potential divider supplies a fraction of input voltage, widely used in sensor circuits.
基尔霍夫节点定律（ΣI = 0）和回路定律（ΣV = 0）用于复杂电路。分压电路提供输入电压的一部分，广泛用于传感器电路。
4. Atomic Structure and the Periodic Table | 原子结构与周期表
Atoms contain protons, neutrons, and electrons. Atomic number Z = number of protons; mass number A = protons + neutrons. Isotopes have the same Z but different neutron numbers.
原子含有质子、中子和电子。原子序数Z = 质子数；质量数A = 质子数 + 中子数。同位素质子数相同而中子数不同。
Electrons fill shells and subshells (s, p, d) in order of increasing energy. Electron configuration determines chemical properties. Periodic trends—such as atomic radius and first ionisation energy—vary across periods and down groups.
电子按能量递增顺序填充壳层和亚层（s, p, d）。电子排布决定化学性质。原子半径和第一电离能等周期性趋势在周期和族中呈规律性变化。
The periodic table arranges elements by increasing atomic number. Shielding and effective nuclear charge explain ionisation energy trends. Groups 1, 2, 17, and 18 show distinct reactive or inert properties.
周期表按原子序数递增排列元素。屏蔽效应和有效核电荷可解释电离能趋势。第1、2、17和18族表现出活泼或惰性特征。
5. Chemical Bonding and Structure | 化学键与结构
Ionic bonding transfers electrons between a metal and a non‑metal, forming a giant ionic lattice. Covalent bonding shares electron pairs between non‑metals, resulting in simple molecular or giant covalent structures.
离子键是金属和非金属间的电子转移，形成巨型离子晶格。共价键是非金属间共享电子对，产生简单分子或巨型共价结构。
Electronegativity differences create polar bonds. VSEPR theory predicts shapes: linear (CO₂), bent (H₂O), trigonal planar (BF₃), tetrahedral (CH₄). Metallic bonding consists of positive ions in a sea of delocalised electrons.
电负性差异产生极性键。VSEPR理论可预测形状：直线形(CO₂)、弯曲形(H₂O)、平面三角形(BF₃)、四面体形(CH₄)。金属键由正离子和离域电子海构成。
Diamond is a hard tetrahedral covalent network (insulator); graphite has layered hexagonal rings with delocalised electrons (soft, conductor). Silicon dioxide (SiO₂) shares the tetrahedral network structure.
金刚石是坚硬的四面体共价网络（绝缘体）；石墨具有层状六边形环和离域电子（软、导电）。二氧化硅(SiO₂)同样具有四面体网络结构。
6. Stoichiometry and Reacting Masses | 化学计量学与反应质量
The mole contains Avogadro’s number (6.02 × 10²³) of particles. Molar mass converts mass to moles and vice versa. Balanced equations reflect mass conservation.
1摩尔含有阿伏伽德罗常数(6.02 × 10²³)个粒子。摩尔质量可实现质量和摩尔数的互算。配平方程式体现质量守恒。
Reacting masses are determined via mole ratios. The empirical formula gives the simplest whole‑number ratio; the molecular formula shows the actual number of atoms in a molecule.
反应质量通过摩尔比确定。实验式给出最简整数比；分子式表示分子中实际原子数目。
Percentage yield = (actual yield / theoretical yield) × 100%. Atom economy evaluates how much of the reactants becomes desired product, important for green chemistry.
产率 = (实际产量/理论产量) × 100%。原子经济性评估反应物转化为目标产物的比例，对绿色化学很重要。
7. Introduction to Organic Chemistry | 有机化学入门
Organic chemistry is based on carbon chains. A homologous series shares the same functional group, general formula, and gradation in physical properties. Examples: alkanes (CₙH₂ₙ₊₂), alkenes (CₙH₂ₙ), alcohols (CₙH₂ₙ₊₁OH).
有机化学基于碳链。同系物具有相同官能团、通式和物理性质递变。例如烷烃(CₙH₂ₙ₊₂)、烯烃(CₙH₂ₙ)、醇(CₙH₂ₙ₊₁OH)。
IUPAC naming identifies the longest carbon chain, numbers substituents and multiple bonds. Structural isomers have the same molecular formula but different connectivity.
IUPAC命名需找出最长碳链，用数字标出取代基和多重键。结构异构体分子式相同但原子连接方式不同。
Alkanes burn in combustion and undergo substitution with halogens. Alkenes readily undergo addition reactions (e.g., hydrogenation, halogenation, hydration) at the C=C double bond. Alcohols can be oxidised to carboxylic acids and form esters.
烷烃可燃烧并与卤素发生取代反应。烯烃因C=C双键易发生加成反应（如加氢、加卤、水合）。醇可被氧化为羧酸并可生成酯。
8. Cell Biology and Membrane Transport | 细胞生物学与膜运输
The cell is the basic unit of life. Prokaryotes (bacteria) lack a nucleus and membrane‑bound organelles; eukaryotes (plants, animals) possess a true nucleus. Organelles such as mitochondria, ribosomes, and ER perform specialised tasks.
细胞是生命的基本单位。原核生物（细菌）无核膜和膜结合细胞器；真核生物（植物、动物）具有真正的细胞核。线粒体、核糖体和内质网等细胞器执行专门功能。
The fluid mosaic model depicts the membrane as a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates. It is selectively permeable, allowing small non‑polar molecules to diffuse freely.
流动镶嵌模型描述膜为磷脂双分子层，镶嵌蛋白质、胆固醇和糖类。它具有选择透过性，允许小非极性分子自由扩散。
Passive transport includes diffusion and facilitated diffusion. Active transport uses ATP to move substances against a concentration gradient. Endocytosis and exocytosis enable bulk transport via vesicles.
被动运输包括扩散和协助扩散。主动运输消耗ATP逆浓度梯度转运物质。胞吞和胞吐通过囊泡实现大块物质运输。
9. Biological Molecules and Enzymes
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