📚 AS AQA Science: Core Concepts Summary | AS AQA 科学：核心知识点梳理
Welcome to this comprehensive revision guide for AS AQA Science, where we distil the most essential ideas from Physics, Chemistry and Biology. Understanding these core concepts will not only boost your exam confidence but also build a strong foundation for A-level study.
欢迎阅读这份 AS AQA 科学综合复习指南，我们提炼了物理、化学和生物学中最关键的理念。掌握这些核心概念不仅能增强你的考试信心，还能为 A-level 学习打下坚实基础。
Each section below presents a topic with clear English explanations immediately followed by their Chinese counterparts, so you can strengthen your bilingual scientific literacy while revising.
以下每一节先给出清晰的英文解释，紧接着提供对应的中文段落，让你在复习的同时提升双语科学素养。
1. Mechanics and Motion | 力学与运动
Kinematics describes how objects move using vector quantities such as displacement, velocity and acceleration. Scalar quantities like speed and distance only have magnitude.
运动学使用位移、速度和加速度等矢量来描述物体的运动。速率和路程等标量只有大小。
The four SUVAT equations connect displacement (s), initial velocity (u), final velocity (v), acceleration (a) and time (t) for uniformly accelerated motion. The equations are v = u + at, s = ut + ½at², v² = u² + 2as, and s = ½(u+v)t.
四个 SUVAT 方程将匀加速运动中的位移(s)、初速度(u)、末速度(v)、加速度(a)和时间(t)联系起来。方程分别为 v = u + at, s = ut + ½at², v² = u² + 2as 和 s = ½(u+v)t。
Newton’s second law states that the net force acting on an object equals its mass multiplied by its acceleration: F = ma. This law explains why a constant force produces a constant acceleration when mass is fixed.
牛顿第二定律指出，作用在物体上的净力等于质量乘以加速度：F = ma。该定律解释了当质量恒定时，恒力产生恒定加速度的原因。
Momentum is defined as the product of mass and velocity (p = mv). The principle of conservation of momentum tells us that in a closed system, total momentum before a collision or explosion equals total momentum afterwards. Impulse delivered by a force equals the change in momentum (FΔt = Δp).
动量定义为质量与速度的乘积 (p = mv)。动量守恒定律指出，在封闭系统中，碰撞或爆炸前的总动量等于碰撞后的总动量。力提供的冲量等于动量的变化 (FΔt = Δp)。
2. Materials and Their Properties | 材料及其性质
Stress is the force applied per unit cross-sectional area (σ = F/A), while strain is the extension per unit original length (ε = ΔL/L). Both are used to characterise the mechanical behaviour of materials.
应力是单位横截面积上施加的力 (σ = F/A)，而应变是单位原始长度的伸长量 (ε = ΔL/L)。两者都用于描述材料的力学行为。
The Young modulus (E) measures a material’s stiffness and is defined as the ratio of tensile stress to tensile strain within the linear elastic region: E = σ/ε. A high Young modulus indicates a stiff material.
杨氏模量 (E) 衡量材料的刚度，定义为在弹性线性区域内拉伸应力与拉伸应变之比：E = σ/ε。杨氏模量高表明材料刚度大。
Stress–strain graphs reveal important features such as the limit of proportionality, elastic limit, yield point and ultimate tensile strength. Ductile materials like copper show a large plastic region, whereas brittle materials like glass fracture with little deformation.
应力–应变图揭示了重要特征，如比例极限、弹性极限、屈服点和极限抗拉强度。铜等延性材料表现出较大的塑性区，而玻璃等脆性材料几乎无变形就断裂。
Hooke’s law states that extension is directly proportional to the applied force up to the limit of proportionality: F = kΔL, where k is the spring constant. Elastic strain energy stored in a stretched spring is ½FΔL or ½k(ΔL)².
胡克定律指出，在比例极限内，伸长量与施加的力成正比：F = kΔL，其中 k 是弹簧常数。储存在拉伸弹簧中的弹性势能为 ½FΔL 或 ½k(ΔL)²。
3. Waves and Optics | 波动与光学
Progressive waves transfer energy without transferring matter. They are characterised by amplitude, wavelength (λ), frequency (f) and wave speed (v), related by v = fλ. Transverse waves oscillate perpendicular to the direction of energy transfer; longitudinal waves oscillate parallel to it.
行波传递能量而不传递物质。它们由振幅、波长 (λ)、频率 (f) 和波速 (v) 描述，关系为 v = fλ。横波的振动方向与能量传递方向垂直；纵波则平行。
The principle of superposition explains how two or more waves combine: when they meet, the resultant displacement is the algebraic sum of the individual displacements. This leads to constructive and destructive interference.
叠加原理解释了两个或多个波如何组合：相遇时合位移等于各独立位移的代数和。这会形成相长干涉和相消干涉。
Standing waves form when two identical waves travelling in opposite directions superpose. Nodes are points of zero displacement; antinodes are points of maximum displacement. The distance between adjacent nodes is λ/2.
当两列相同且反向传播的波叠加时，会形成驻波。波节是位移为零的点；波腹是位移最大的点。相邻波节之间的距离为 λ/2。
Refraction occurs when waves change speed at a boundary between two media. Snell’s law relates the angles of incidence and refraction to the refractive indices: n₁sinθ₁ = n₂sinθ₂. Total internal reflection can happen when light travels from a denser to a less dense medium at angles greater than the critical angle.
当波在两种介质边界改变速度时会发生折射。斯涅尔定律将入射角和折射角与折射率联系起来：n₁sinθ₁ = n₂sinθ₂。当光从光密介质射向光疏介质且入射角大于临界角时，会发生全内反射。
4. Atomic Structure and Periodicity | 原子结构与周期性
Atoms are composed of protons, neutrons and electrons. The atomic number (Z) is the number of protons, and the mass number (A) is the total number of protons and neutrons. Isotopes are atoms of the same element with different numbers of neutrons.
原子由质子、中子和电子组成。原子序数 (Z) 是质子数，质量数 (A) 是质子数和中子数之和。同位素是同一元素中中子数不同的原子。
Electron arrangement is described using principal quantum shells (n=1,2,3…) and subshells (s, p, d). The filling order follows the Aufbau principle: 1s, 2s, 2p, 3s, 3p, 4s, 3d. Each orbital holds a maximum of two electrons with opposite spins.
电子排布用主量子壳层 (n=1,2,3…) 和亚层 (s, p, d) 描述。填充顺序遵循构造原理：1s, 2s, 2p, 3s, 3p, 4s, 3d。每个轨道最多容纳两个自旋相反的电子。
First ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms, forming one mole of gaseous 1+ ions: X(g) → X⁺(g) + e⁻. Ionisation energies show a general increase across a period and decrease down a group, with small drops caused by subshell changes.
第一电离能是指从一摩尔气态原子中移去一摩尔电子，形成一摩尔气态 1+ 离子所需的能量：X(g) → X⁺(g) + e⁻。电离能在同一周期中通常递增，在同一族中递减，亚层变化会引起小幅下降。
The periodic table is arranged by atomic number. Elements in the same group have similar chemical properties because they have the same outer-shell electron configuration. Period 3 trends can be explained by increasing nuclear charge and similar shielding.
周期表按原子序数排列。同族元素具有相似化学性质，因为它们具有相同的外层电子排布。第三周期的变化趋势可由核电荷增加和屏蔽效应相似来解释。
5. Bonding and Structure | 化学键合与结构
Ionic bonding involves the transfer of electrons from a metal to a non-metal, forming positive cations and negative anions held together by strong electrostatic forces. Giant ionic lattices have high melting points and conduct electricity when molten or dissolved.
离子键涉及电子从金属向非金属的转移，形成正阳离子和负阴离子，通过强静电吸引力结合。巨型离子晶格具有高熔点，在熔融或溶解时导电。
Covalent bonding is the sharing of electron pairs between non-metal atoms. Simple molecular substances like H₂O and CO₂ have low melting points due to weak intermolecular forces, while giant covalent structures like diamond and silicon dioxide are very hard and have extremely high melting points.
共价键是非金属原子间共享电子对。H₂O 和 CO₂ 等简单分子物质因分子间作用力弱而熔点低，而金刚石和二氧化硅等巨型共价结构非常坚硬，熔点极高。
Electronegativity is the ability of an atom to attract the bonding pair of electrons in a covalent bond. A large electronegativity difference leads to a polar bond. The shape of molecules is predicted by VSEPR theory: linear (180°), trigonal planar (120°), tetrahedral (109.5°), etc.
电负性是一个原子在共价键中吸引共用电子对的能力。电负性差异大会导致极性键。分子的形状可由 VSEPR 理论预测：直线形 (180°)、平面三角形 (120°)、四面体形 (109.5°) 等。
Metallic bonding consists of a lattice of positive metal ions surrounded by a sea of delocalised electrons. This explains the electrical conductivity, malleability and ductility of metals. The strength of metallic bonds depends on the charge of the cation and the number of delocalised electrons per atom.
金属键由正金属离子晶格和其周围的离域电子海构成。这解释了金属的导电性、延展性和可塑性。金属键的强度取决于阳离子电荷以及每个原子可贡献的离域电子数。
6. Quantitative Chemistry and Energetics | 定量化学与能量学
The mole is the amount of substance containing 6.02 × 10²³ particles. The molar mass (M) is the mass of one mole of a substance in g mol⁻¹. Amount n = m / M. Reaction stoichiometry uses balanced equations to determine the proportions of reactants and products.
摩尔是含有 6.02 × 10²³ 个微粒的物质的量。摩尔质量 (M) 是一摩尔物质的质量，单位为 g mol⁻¹。物质的量 n = m / M。反应计量学利用配平的方程式确定反应物与生成物的比例。
The ideal gas equation is pV = nRT, where p is pressure (Pa), V is volume (m³), n is number of moles, R = 8.31 J mol⁻¹ K⁻¹, and T is temperature (K). This equation can be used to calculate the molar mass or molecular formula of a volatile substance.
理想气体方程为 pV = nRT，其中 p 为压强 (Pa)，V 为体积 (m³)，n 为摩尔数，R = 8.31 J mol⁻¹ K⁻¹，T 为温度 (K)。该方程可用于计算挥发性物质的摩尔质量或分子式。
Enthalpy change (ΔH) is the heat energy transferred at constant pressure. Exothermic reactions (ΔH negative) release energy, while endothermic reactions (ΔH positive) absorb energy. Calorimetry experiments measure temperature change to calculate q = mcΔT and then ΔH.
焓变 (ΔH) 是恒压下传递的热能。放热反应 (ΔH 为负) 释放能量，吸热反应 (ΔH 为正) 吸收能量。量热实验通过测量温度变化计算 q = mcΔT，再求得 ΔH。
Hess’s law states that the total enthalpy change for a reaction is independent of the route taken. This allows the calculation of ΔH for reactions that are difficult to measure directly, using enthalpy of formation (ΔH_f) or combustion (ΔH_c) cycles.
赫斯定律指出，一个化学反应的总焓变与所采取的途径无关。可以利用生成焓 (ΔH_f) 或燃烧焓 (ΔH_c) 的循环，计算出难以直接测量的反应的 ΔH。
7. Biological Molecules and Enzymes | 生物分子与酶
Carbohydrates include monosaccharides (e.g. glucose, C₆H₁₂O₆), disaccharides (e.g. sucrose, maltose) and polysaccharides (e.g. starch, glycogen, cellulose). Monosaccharides are linked by glycosidic bonds formed in condensation reactions.
碳水化合物包括单糖 (如葡萄糖 C₆H₁₂O₆)、二糖 (如蔗糖、麦芽糖) 和多糖 (如淀粉、糖原、纤维素)。单糖通过缩合反应形成的糖苷键连接。
Lipids, such as triglycerides, are composed of one glycerol molecule and three fatty acids joined by ester bonds. Phospholipids have a hydrophilic head and hydrophobic tails, making them essential for cell membrane formation.
脂质，如甘油三酯，由一个甘油分子和三个脂肪酸通过酯键连接而成。磷脂具有亲水头部和疏水尾部，对细胞膜的形成至关重要。
Proteins are polymers of amino acids linked by peptide bonds. The primary structure is the amino acid sequence. Secondary structures include alpha-helices and beta-pleated sheets, stabilised by hydrogen bonds. Tertiary structure is the overall 3D folding, held by hydrogen bonds, ionic bonds, disulfide bridges and hydrophobic interactions.
蛋白质是由氨基酸通过肽键连接而成的聚合物。一级结构是氨基酸序列。二级结构包括 α-螺旋和 β-折叠，由氢键稳定。三级结构是整体的三维折叠，由氢键、离子键、二硫键和疏水相互作用维持。
Enzymes are biological catalysts that lower the activation energy of a reaction. The active site is complementary to the substrate, explained by the lock-and-key model and the induced-fit model. Enzyme activity is affected by temperature, pH, substrate concentration and the presence of inhibitors.
酶是生物催化剂，能降低反应的活化能。活性中心与底物互补，可用锁钥模型和诱导契合模型解释。酶活性受温度、pH、底物浓度和抑制剂存在的影响。
8. Cell Structure and Membrane Transport | 细胞结构与膜运输
Eukaryotic cells have a distinct nucleus and membrane-bound organelles such as mitochondria, endoplasmic reticulum, Golgi apparatus and lysosomes. Prokaryotic cells lack a nucleus and organelles but may contain plasmids and a cell wall made of peptidoglycan.
真核细胞具有明晰的细胞核以及线粒体、内质网、高尔基体和溶酶体等膜包被的细胞器。原核细胞没有细胞核和膜性细胞器，但可能含有质粒和由肽聚糖构成的细胞壁。
The cell surface membrane is described by the fluid mosaic model: a phospholipid bilayer with embedded proteins, cholesterol and glycoproteins. It is selectively permeable, allowing passive and active transport.
细胞膜可用流动镶嵌模型描述：磷脂双分子层中镶嵌着蛋白质、胆固醇和糖蛋白。它具有选择透过性，允许被动运输和主动运输。
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration, down a concentration gradient. Facilitated diffusion uses channel and carrier proteins but still requires no metabolic energy.
扩散是粒子从较高浓度区域向较低浓度区域的净移动，顺浓度梯度。易化扩散利用通道蛋白和载体蛋白，但仍不需代谢能量。
Active transport moves substances against their concentration gradient using energy from ATP, often via specific carrier proteins. Osmosis is the diffusion of water across a partially permeable membrane from a region of higher water potential to a region of lower water potential.
主动运输利用 ATP 提供的能量，通常通过特异性载体蛋白将物质逆浓度梯度运输。渗透是水通过部分通透膜从较高水势区域向较低水势区域的扩散。
9. The Immune System | 免疫系统
The immune system defends the body through non-specific (innate) and specific (adaptive) responses. Physical barriers like skin, mucous membranes and stomach acid form the first line of defence. Phagocytosis is a key non-specific response, where phagocytes engulf and digest pathogens.
免疫系统通过非特异性 (先天) 和特异性 (适应性) 反应来防御机体。皮肤、黏膜和胃酸等物理屏障构成第一道防线。吞噬作用是一种关键的非特异性反应，吞噬细胞吞噬并消化病原体。
Specific immunity involves lymphocytes. T lymphocytes recognise antigens presented on infected cells and either help activate B cells or kill the infected cells directly. B lymphocytes produce antibodies that bind specifically to antigens, neutralising toxins and marking pathogens for destruction.
特异性免疫涉及淋巴细胞。T 淋巴细胞识别被感染细胞呈递的抗原，辅助激活 B 细胞或直接杀伤受感染细胞。B 淋巴细胞产生抗体，特异性结合抗原，中和毒素并标记病原体以供破坏。
Each antibody has a variable region with a unique binding site for a specific antigen. The antibody–antigen interaction can lead to agglutination, making it easier for phagocytes to engulf the pathogens. The structure includes heavy chains and light chains held together by disulfide bonds.
每种抗体具有可变区，携带针对特定抗原的独特结合位点。抗体-抗原相互作用可导致凝集，便于吞噬细胞吞噬病原体。抗体结构由重链和轻链通过二硫键连接而成。
Immunological memory is the basis of vaccination. After exposure to a pathogen, memory B and T cells remain in the body and can mount a faster, stronger secondary immune response upon re-infection, often preventing illness entirely.
免疫记忆是疫苗接种的基础。初次暴露于病原体后，记忆 B 细胞和记忆 T 细胞留在体内，再感染时能发起更快、更强的二次免疫应答，通常可完全防止疾病发生。
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