📚 Year 11 CAIE Science: Core Knowledge Review | CAIE 科学核心知识点梳理
Preparing for the CAIE IGCSE Science exams (whether you are taking Combined Science or Co-ordinated Sciences) requires a clear understanding of the fundamental principles that link biology, chemistry and physics. This revision guide organises the most important core knowledge across the three disciplines, helping Year 11 learners focus their revision on key concepts, definitions and calculations that frequently appear in examination papers. Every section is presented in a concise yet thorough manner, with English explanations followed immediately by their Chinese equivalents to support bilingual mastery.
准备 CAIE IGCSE 科学考试（无论你学习的是 Combined Science 还是 Co-ordinated Sciences）都需要清晰地掌握连接生物、化学和物理的基本原理。这份复习指南整理了三个学科中最重要的核心知识，帮助 Year 11 学生将复习重点放在考试中经常出现的核心概念、定义和计算上。每个部分都以简洁而透彻的方式呈现，英文解释紧跟中文翻译，以支持双语掌握。
1. Cell Structure and Function | 细胞结构与功能
All living organisms are composed of cells, which can be classified as prokaryotic or eukaryotic. Animal and plant cells are eukaryotic, sharing a cell membrane, cytoplasm and nucleus containing genetic material. Plant cells differ by having a rigid cell wall made of cellulose, a large permanent vacuole for storage and support, and chloroplasts that carry out photosynthesis.
所有生物都由细胞组成，细胞可分为原核细胞和真核细胞。动物细胞和植物细胞都是真核细胞，都拥有细胞膜、细胞质和含有遗传物质的细胞核。植物细胞的区别在于有由纤维素组成的坚硬细胞壁、一个用于储存和支撑的永久性大液泡，以及进行光合作用的叶绿体。
Within the cytoplasm, organelles perform specialised tasks. Mitochondria are the site of aerobic respiration, releasing energy stored in glucose. Ribosomes, which can be free or attached to rough endoplasmic reticulum, are responsible for protein synthesis. The Golgi apparatus modifies and packages proteins for secretion.
在细胞质中，细胞器执行特定的功能。线粒体是有氧呼吸的场所，释放葡萄糖中储存的能量。核糖体可以是游离的，也可以附着在粗面内质网上，负责蛋白质的合成。高尔基体负责修饰和包装蛋白质以便分泌。
Cell specialisation allows multicellular organisms to divide labour. Red blood cells lose their nucleus to carry more haemoglobin, nerve cells have long axons for transmitting impulses, and root hair cells in plants increase surface area for water absorption.
细胞的分化使得多细胞生物能够进行分工。红细胞失去细胞核以携带更多的血红蛋白，神经细胞有长长的轴突用于传导冲動，植物的根毛细胞增大表面积以便吸收水分。
Diffusion, osmosis and active transport are the three main processes by which substances move across cellular membranes. Diffusion is the net movement of particles from high to low concentration, while osmosis is the diffusion of water through a partially permeable membrane. Active transport requires energy (ATP) to move substances against their concentration gradient.
扩散、渗透和主动运输是物质穿过细胞膜的三种主要方式。扩散是粒子从高浓度区向低浓度区的净移动，而渗透是水通过部分渗透膜的扩散。主动运输需要能量（ATP）来逆浓度梯度移动物质。
2. Enzymes and Digestion | 酶与消化
Enzymes are biological catalysts made of protein that speed up metabolic reactions without being consumed. They have a specific active site that is complementary to the shape of their substrate, leading to the lock-and-key model of enzyme action. Enzyme activity is affected by temperature and pH; extremes can denature the enzyme, changing the active site's shape permanently.
酶是由蛋白质构成的生物催化剂，能加速代谢反应而本身不被消耗。它们有一个特定的活性位点，与其底物的形状互补，这导致了酶作用的锁钥模型。酶的活性受温度和 pH 的影响；极端的条件会使酶变性，永久地改变活性位点的形状。
Digestive enzymes break down large, insoluble food molecules into small, soluble ones for absorption. Amylase, produced in the salivary glands and pancreas, catalyses the breakdown of starch into maltose. Proteases, such as pepsin in the stomach and trypsin in the small intestine, convert proteins into amino acids. Lipase, secreted by the pancreas, digests fats into fatty acids and glycerol.
消化酶将大的、不溶性的食物分子分解成小的、可溶性的分子以便吸收。淀粉酶由唾液腺和胰腺分泌，催化淀粉分解为麦芽糖。蛋白酶，如胃中的胃蛋白酶和小肠中的胰蛋白酶，将蛋白质转化为氨基酸。脂肪酶由胰腺分泌，将脂肪消化为脂肪酸和甘油。
The products of digestion are absorbed mainly in the small intestine, which has villi and microvilli to increase surface area. The villi also contain a lacteal for lipid absorption and a dense capillary network to transport amino acids and simple sugars into the bloodstream.
消化的产物主要在小肠被吸收，小肠内壁有小肠绒毛和微绒毛以增大表面积。绒毛内还含有乳糜管以吸收脂类，以及密集的毛细血管网将氨基酸和单糖转运入血液。
3. Transport in Plants and Animals | 动植物体内的运输
In flowering plants, xylem tissue transports water and dissolved mineral ions from the roots to the leaves, driven by transpiration pull. Xylem vessels are composed of dead, hollow cells arranged end-to-end with lignified walls that provide support. Phloem tissue, made of living sieve tube elements and companion cells, translocates sucrose and amino acids to growing and storage organs.
在开花植物中，木质部组织在蒸腾拉力的驱动下，将水和溶解的矿物离子从根部输送到叶片。木质部导管由死去的、中空的细胞端对端排列组成，细胞壁木质化，提供了支撑。韧皮部组织由活的筛管分子和伴胞组成，负责将蔗糖和氨基酸转运到生长和储存器官。
The human circulatory system consists of the heart, blood vessels and blood. The heart is a double pump: the right side sends deoxygenated blood to the lungs, while the left side pumps oxygenated blood to the rest of the body. Arteries have thick, elastic walls to withstand high pressure, veins have valves to prevent backflow, and capillaries have walls one cell thick to allow efficient exchange.
人的循环系统由心脏、血管和血液组成。心脏是一个双重泵：右心室将缺氧血泵入肺部，左心室将含氧血泵送至身体其余部分。动脉有厚而富有弹性的管壁以承受高压，静脉有瓣膜以防止回流，毛细血管管壁仅一个细胞的厚度，有利于高效的物质交换。
Blood plasma transports carbon dioxide, hormones, glucose and waste products. Red blood cells contain haemoglobin, which binds oxygen reversibly, forming oxyhaemoglobin in areas of high oxygen concentration. White blood cells defend the body against pathogens, and platelets are involved in blood clotting.
血浆运输二氧化碳、激素、葡萄糖和废物。红细胞含有血红蛋白，能可逆地与氧结合，在氧浓度高的区域形成氧合血红蛋白。白细胞保护身体免受病原体侵害，血小板参与血液凝固。
4. Atomic Structure and Bonding | 原子结构与化学键
Atoms consist of a central nucleus containing positively charged protons and neutral neutrons, surrounded by negatively charged electrons arranged in shells or energy levels. The atomic number (Z) equals 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.
原子由包含带正电的质子和不带电的中子的原子核，以及周围按壳层或能级排列的带负电的电子组成。原子序数 (Z) 等于质子数，质量数 (A) 是质子与中子的总数。同位素是同一种元素中具有不同中子数的原子。
Ionic bonding occurs when electrons are transferred from a metal atom to a non-metal atom, forming positively charged cations and negatively charged anions. The strong electrostatic forces of attraction between oppositely charged ions create a giant ionic lattice with high melting and boiling points. Sodium chloride (NaCl) is a classic example: Na atoms lose one electron to become Na⁺, while Cl atoms gain one electron to become Cl⁻.
当电子从金属原子转移到非金属原子时，形成离子键，产生带正电的阳离子和带负电的阴离子。相反电荷离子之间强的静电吸引力形成具有高熔点和沸点的巨型离子晶格。氯化钠 (NaCl) 是一个典型例子：钠原子失去一个电子变成 Na⁺，而氯原子获得一个电子变成 Cl⁻。
Covalent bonding involves the sharing of electron pairs between non-metal atoms. Simple molecular substances like water (H₂O) and carbon dioxide (CO₂) have strong covalent bonds within molecules but weak intermolecular forces, leading to low melting and boiling points. Giant covalent structures, such as diamond and silicon dioxide, have many strong covalent bonds throughout, making them extremely hard and giving them very high melting points.
共价键涉及非金属原子之间共用电子对。像水 (H₂O) 和二氧化碳 (CO₂) 等简单分子物质，分子内共价键强，但分子间力弱，因此熔点和沸点低。巨型共价结构，如金刚石和二氧化硅，整个结构中有大量强的共价键，这使得它们极其坚硬并有很高的熔点。
5. Moles and Chemical Equations | 摩尔与化学方程式
The mole is the unit for amount of substance, defined as the amount containing 6.02 x 10²³ particles (Avogadro's constant). One mole of atoms of an element has a mass in grams equal to its relative atomic mass (Ar). The relative formula mass (Mr) of a compound is the sum of the Ar values of all the atoms in one formula unit.
摩尔是物质的量的单位，定义为含有 6.02 × 10²³ 个微粒 (阿伏伽德罗常数) 的量。一摩尔任何元素的原子的质量克数等于其相对原子质量 (Ar)。化合物的相对化学式量 (Mr) 是一个化学式单元中所有原子 Ar 值之和。
Balanced chemical equations respect the law of conservation of mass, showing the number of moles of each reactant and product. For example, the balanced equation for the reaction between hydrogen and oxygen is: 2H₂ + O₂ → 2H₂O. From the coefficients, two moles of hydrogen react with one mole of oxygen to produce two moles of water.
平衡的化学方程式遵循质量守恒定律，显示了每种反应物和生成物的摩尔数。例如，氢气和氧气反应的平衡方程式为：2H₂ + O₂ → 2H₂O。从系数来看，两摩尔氢气与一摩尔氧气反应生成两摩尔水。
10 g of calcium carbonate (CaCO₃) is heated, the mass of calcium oxide (CaO) produced can be found by first calculating moles of CaCO₃, then linking moles to CaO via the balanced equation, and finally converting back to mass. This approach is essential for solving stoichiometry problems.
利用摩尔概念，我们可以计算反应质量。摩尔数 = 质量 (g) / 摩尔质量 (g/mol)。如果加热 10 克碳酸钙 (CaCO₃)，要得到生成的氧化钙质量，可以先计算 CaCO₃ 的摩尔数，然后通过平衡方程式与 CaO 的摩尔数关联，最后转换回质量。这是解决化学计量问题的基本方法。
6. Acids, Bases and Salts | 酸、碱和盐
An acid is a substance that produces hydrogen ions (H⁺) in aqueous solution. Strong acids like hydrochloric acid (HCl) ionise completely, while weak acids such as ethanoic acid (CH₃COOH) only partially ionise. Bases are substances that react with acids to form a salt and water; alkalis are soluble bases that release hydroxide ions (OH⁻) in solution.
酸是在水溶液中能产生氢离子 (H⁺) 的物质。强酸如盐酸 (HCl) 完全电离，而弱酸如乙酸 (CH₃COOH) 仅部分电离。碱是能与酸反应生成盐和水的物质；可溶性碱能在溶液中释放氢氧根离子 (OH⁻)，称为可溶性碱。
The pH scale measures acidity and alkalinity, ranging from 0 (strongly acidic) to 14 (strongly alkaline), with 7 being neutral. Universal indicator, litmus and other indicators show colour changes across the pH range. Neutralisation reactions between an acid and an alkali produce a salt and water: H⁺(aq) + OH⁻(aq) → H₂O(l).
pH 值用来量度酸碱度，范围从 0（强酸性）到 14（强碱性），7 为中性。通用指示剂、石蕊试纸和其他指示剂在 pH 范围内显示不同的颜色变化。酸和碱的中和反应生成盐和水：H⁺(aq) + OH⁻(aq) → H₂O(l)。
Salts can be prepared by various methods. Soluble salts are often made by reacting an acid with an insoluble base (such as a metal oxide or carbonate) and then crystallising. Preparation of insoluble salts involves a precipitation reaction, mixing two aqueous solutions containing the required ions. The salt's name comes from the acid and the metal: sulfuric acid gives sulfates, nitric acid gives nitrates, and hydrochloric acid gives chlorides.
盐可以通过多种方法制备。可溶性盐通常通过酸与不溶性碱（如金属氧化物或碳酸盐）反应，然后结晶来制取。不溶性盐的制备涉及沉淀反应，将两种含有所需离子的溶液混合。盐的名称来源于所用的酸和金属：硫酸生成硫酸盐，硝酸生成硝酸盐，盐酸生成氯化物。
7. Forces and Motion | 力与运动
Speed is the distance travelled per unit time, while velocity is speed in a given direction. Acceleration is the rate of change of velocity. A distance-time graph shows how distance changes with time; a straight line represents constant speed, and the gradient gives the speed. A velocity-time graph has a gradient equal to acceleration, and the area under the graph equals the distance travelled.
速率是单位时间内经过的路程，而速度是给定方向上的速率。加速度是速度变化的速率。路程-时间图像显示路程如何随时间变化；直线代表匀速，斜率表示速率。速度-时间图像的斜率等于加速度，图像下的面积等于经过的路程。
Newton's first law states that a body remains at rest or in uniform motion unless acted on by a resultant force. Newton's second law relates resultant force (F), mass (m) and acceleration (a) by the equation: F = m × a. Newton's third law asserts that if body A exerts a force on body B, body B exerts an equal and opposite force on body A.
牛顿第一定律指出，物体在不受合力作用时，会保持静止或匀速直线运动状态。牛顿第二定律用公式关联了合力 (F)、质量 (m) 和加速度 (a)：F = m × a。牛顿第三定律表明，如果物体 A 对物体 B 施加一个力，那么物体 B 会对 A 施加一个大小相等、方向相反的力。
Momentum is the product of mass and velocity: p = m × v. In a closed system, the total momentum before a collision or explosion equals the total momentum after, illustrating the principle of conservation of momentum. This is widely used to analyse car collisions and rocket propulsion.
动量是质量与速度的乘积：p = m × v。在一个封闭系统中，碰撞或爆炸前的总动量等于之后的总动量，这体现了动量守恒定律。这被广泛用于分析汽车碰撞和火箭推进。
8. Energy Transfers and Work | 能量转移与功
Energy exists in many forms, including kinetic, gravitational potential, thermal, chemical, nuclear, sound and light. The law of conservation of energy states that energy cannot be created or destroyed, only transferred or converted from one form to another. When energy is transferred mechanically, work is done.
能量以多种形式存在，包括动能、引力势能、热能、化学能、核能、声能和光能。能量守恒定律指出，能量不能被创造或毁灭，只能从一种形式转移或转化为另一种形式。当能量以机械方式转移时，就做了功。
Work done (W) equals force multiplied by distance moved in the direction of the force: W = F × d. Gravitational potential energy gained by an object lifted to a height h is: ΔEₚ = m × g × h, where g is the gravitational field strength (10 N/kg on Earth). Kinetic energy is given by: Eₖ = ½ × m × v².
做功 (W) 等于力乘以在力的方向上移动的距离：W = F × d。物体被举升到高度 h 所获得的引力势能为：ΔEₚ = m × g × h，其中 g 是重力场强度（地球上为 10 N/kg）。动能由公式给出：Eₖ = ½ × m × v²。
Power is the rate of doing work or transferring energy: P = E/t. The unit of power is the watt (W), equivalent to joules per second. Efficiency is the ratio of useful output energy to total input energy, often expressed as a percentage: Efficiency = (useful output energy / total input energy) × 100%.
功率是做功或转移能量的速率：P = E/t。功率的单位是瓦特 (W)，相当于焦耳每秒。效率是有用输出能量与总输入能量之比，通常表示为百分比：效率 = (有用输出能量 / 总输入能量) × 100%。
9. Electricity and Circuits | 电与电路
Electric current (I) is the rate of flow of charge, measured in amperes (A). In a metallic conductor, current is carried by moving electrons. Potential difference (V), measured in volts, is the energy transferred per unit charge between two points in a circuit. Resistance (R), measured in ohms (Ω), opposes the flow of current.
电流 (I) 是电荷流动的速率，单位为安培 (A)。在金属导线中，电流由移动的电子携带。电势差 (V) 以伏特为单位，是电路中两点之间单位电荷转移的能量。电阻 (R) 以欧姆 (Ω) 为单位，阻碍电流的流动。
Ohm's law states that the current through a conductor is directly proportional to the potential difference across it, provided temperature remains constant: V = I × R. Resistors, lamps and diodes are common circuit components; only a fixed resistor obeys Ohm's law exactly, while a filament lamp's resistance increases with temperature.
欧姆定律指出，在温度保持不变的情况下，通过导体的电流与其两端电势差成正比：V = I × R。电阻器、灯泡和二极管是常见的电路元件；只有固定电阻器严格遵循欧姆定律，而灯丝灯泡的电阻随温度升高而增大。
al) = R₁ + R₂ + ... . In parallel circuits, each component gets the full supply voltage, and the total current is the sum of currents in each branch. The combined resistance decreases as more branches are added.
串联电路只有一条电流通路，因此各处电流相等。总电阻是个别电阻之和：R(总) = R₁ + R₂ + …。在并联电路中，每个元件获得全部电源电压，总电流等于各支路电流之和。随着并联支路增加，总电阻减小。
10. Waves and Their Properties | 波及其性质
Waves transfer energy from one place to another without transferring matter. Transverse waves, such as light and water waves, have oscillations perpendicular to the direction of energy transfer, while longitudinal waves, like sound, have oscillations parallel to the direction of travel. Examples of longitudinal waves include compressions and rarefactions in air.
波将能量从一个地方传递到另一个地方而不传递物质。横波，如光波和水波，振动方向与能量传递方向垂直；纵波，如声波，振动方向与传播方向平行。纵波的例子包括空气中的压缩和稀疏。
The amplitude of a wave is the maximum displacement from the rest position. Wavelength (λ) is the distance between two consecutive crests or compressions. Frequency (f) is the number of complete waves passing a point per second, measured in hertz (Hz). The wave equation links speed (v), frequency and wavelength: v = f × λ.
波的振幅是离开平衡位置的最大位移。波长 (λ) 是两个相邻波峰或密部之间的距离。频率 (f) 是每秒通过某点的完整波数，单位为赫兹 (Hz)。波速方程关联波速 (v)、频率和波长：v = f × λ。
tion (angle of incidence = angle of reflection). Refraction happens when waves change speed as they pass from one medium to another, causing a change in direction. Diffraction is the spreading of waves around obstacles or through gaps, most noticeable when the gap size is similar to the wavelength.
波的行为包括反射、折射和衍射。反射发生在波从表面反弹时，遵循反射定律（入射角等于反射角）。折射是波在从一种介质进入另一种介质时，波速改变导致方向改变。衍射是波遇到障碍物或通过狭缝时发生扩展的现象，当狭缝大小与波长相当时最为明显。
rared, visible light, ultraviolet, X-rays and gamma rays. All travel at the same speed in a vacuum (3.0 × 10⁸ m/s). Each region has distinct uses and dangers, such as microwaves for heating food and X-rays for medical imaging, but with associated risks like burns or DNA damage.
电磁波谱按频率增加、波长减小的顺序排列：无线电波、微波、红外线、可见光、紫外线、X 射线和伽马射线。所有电磁波在真空中以相同速度 (3.0 × 10⁸ 米/秒) 传播。每个波段都有特定的用途和危害，例如微波用于加热食物，X 射线用于医学成像，但也有相关的风险，如灼伤或 DNA 损伤。
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