📚 Core Concepts for Year 11 Cambridge Science | Year 11 剑桥科学核心知识点梳理
Cambridge IGCSE Science (Co-ordinated Sciences or Combined Science) equips Year 11 students with a deep understanding of key principles in biology, chemistry and physics. This revision guide distils the essential core topics, giving you a clear, bilingual summary to reinforce your knowledge for the final examination.
剑桥 IGCSE 科学（协调科学或综合科学）帮助 Year 11 学生深入理解生物、化学和物理的核心原理。本复习指南浓缩了必须掌握的重要主题，提供清晰的双语总结，巩固你的知识，为最终考试做好充分准备。
1. Cell Biology and Transport | 细胞生物学与运输
All living organisms are made of cells, the basic structural and functional units of life. Plant cells are distinguished by a rigid cellulose cell wall, chloroplasts for photosynthesis, and a large permanent vacuole that maintains turgor pressure. Animal cells lack these features but share common organelles such as the nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.
所有生物体都由细胞构成，细胞是生命的基本结构和功能单位。植物细胞的显著特征包括坚硬的纤维素细胞壁、进行光合作用的叶绿体以及维持膨压的大液泡。动物细胞没有这些结构，但共有的细胞器包括细胞核、细胞质、细胞膜、线粒体和核糖体。
Substances move across the cell membrane by three main processes. Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient, requiring no energy. Osmosis is the diffusion of water molecules through a partially permeable membrane from a dilute solution to a more concentrated solution. Active transport moves ions or molecules against a concentration gradient, using energy from respiration.
物质跨膜运输主要通过三种方式。扩散是粒子顺浓度梯度从高浓度区域向低浓度区域的净运动，不需要能量。渗透是水分子通过部分透膜从稀溶液向浓溶液的扩散。主动运输则是逆浓度梯度运输离子或分子，依靠呼吸作用释放的能量。
2. Enzymes and Digestion | 酶与消化
Enzymes are biological catalysts made of protein that speed up chemical reactions in living organisms without being used up. Each enzyme has an active site with a specific shape that fits its substrate, often described by the lock-and-key model. Enzyme activity is affected by temperature and pH; extremely high temperatures denature the enzyme by changing the shape of the active site permanently.
酶是由蛋白质构成的生物催化剂，能加速生物体内的化学反应而本身不被消耗。每种酶都有一个特定形状的活性位点，与底物相互契合，常用锁钥模型来描述。酶活性受温度和 pH 影响；极高的温度会使酶变性，永久性地改变活性位点的形状。
In human digestion, large food molecules are broken down into smaller, soluble molecules that can be absorbed into the blood. Amylase (produced in the salivary glands and pancreas) digests starch into maltose; proteases (stomach and pancreas) break proteins into amino acids; lipases (pancreas) digest fats into fatty acids and glycerol. Bile, produced in the liver and stored in the gall bladder, emulsifies fats and creates an alkaline environment for lipase to work.
在人体消化过程中，大分子食物被分解为可溶的小分子，以便被血液吸收。淀粉酶（由唾液腺和胰腺分泌）将淀粉分解为麦芽糖；蛋白酶（胃和胰腺）将蛋白质分解为氨基酸；脂肪酶（胰腺）将脂肪分解为脂肪酸和甘油。肝脏产生并储存于胆囊的胆汁能乳化脂肪，并为脂肪酶的作用创造碱性环境。
3. Photosynthesis and Plant Nutrition | 光合作用与植物营养
Photosynthesis is the process by which green plants convert light energy into chemical energy, using carbon dioxide and water to produce glucose and oxygen. Chlorophyll in chloroplasts absorbs light, primarily in the red and blue regions of the spectrum. The rate of photosynthesis is limited by light intensity, carbon dioxide concentration and temperature.
光合作用是绿色植物将光能转化为化学能的过程，利用二氧化碳和水生成葡萄糖和氧气。叶绿体中的叶绿素吸收光线，主要是光谱中的红光和蓝光区域。光合作用速率受光照强度、二氧化碳浓度和温度的限制。
The balanced equation for photosynthesis is:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Plants also require mineral ions absorbed through the roots. Nitrate ions are needed for the synthesis of amino acids and proteins; magnesium ions are essential for making chlorophyll. A deficiency of nitrate results in stunted growth, while a lack of magnesium leads to yellowing of leaves (chlorosis).
植物还需要通过根部吸收矿质离子。硝酸根离子用于合成氨基酸和蛋白质；镁离子是制造叶绿素所必需的。缺氮会导致生长迟缓，缺镁则会引起叶片黄化（缺绿症）。
4. Respiration and Gas Exchange | 呼吸作用与气体交换
Aerobic respiration releases energy from glucose in the presence of oxygen, producing carbon dioxide and water. The process takes place in mitochondria and can be summarised as:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ ATP)
Anaerobic respiration occurs when oxygen is in short supply. In muscles, glucose is broken down to lactic acid, releasing a small amount of energy. In yeast, anaerobic respiration produces ethanol and carbon dioxide (fermentation).
有氧呼吸在氧气参与下从葡萄糖中释放能量，产生二氧化碳和水。这一过程发生在线粒体中，可简化为：C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ ATP)。无氧呼吸在氧气不足时发生。在肌肉中，葡萄糖被分解为乳酸，释放少量能量。在酵母中，无氧呼吸产生乙醇和二氧化碳（发酵）。
In humans, the gas exchange system consists of the trachea, bronchi, bronchioles and alveoli. Alveoli provide a large surface area, thin walls, a rich blood supply and a moist surface to maximise the diffusion of oxygen into the blood and carbon dioxide out of the blood. Breathing movements (ventilation) are brought about by the contraction and relaxation of the intercostal muscles and the diaphragm.
人体的气体交换系统包括气管、支气管、细支气管和肺泡。肺泡提供了巨大的表面积、极薄的壁、丰富的血液供应和湿润的表面，以最大限度地促进氧气进入血液和二氧化碳排出血液。呼吸运动（通气）由肋间肌和膈肌的收缩与舒张实现。
5. Atomic Structure and Bonding | 原子结构与化学键
All matter is composed of atoms, each consisting of a nucleus (containing protons and neutrons) surrounded by electrons arranged in shells. The atomic number is the number of protons, determining the element; the mass number is the total number of protons and neutrons. Electrons occupy the lowest available energy levels, with a maximum of 2 in the first shell and 8 in the second shell.
所有物质由原子组成，每个原子包含一个原子核（由质子和中子构成）以及核外分层排布的电子。原子序数是质子数，决定了元素的种类；质量数是质子与中子数的总和。电子优先占据最低能级，第一层最多容纳 2 个电子，第二层最多容纳 8 个电子。
Chemical bonding allows atoms to achieve a full outer shell, typically 8 electrons (octet rule). Ionic bonding involves the transfer of electrons from a metal to a non-metal, forming oppositely charged ions held together by strong electrostatic forces. Ionic compounds have high melting points and conduct electricity when molten or dissolved. Covalent bonding occurs between non-metal atoms that share pairs of electrons; simple molecular substances (e.g. CO₂, H₂O) have low melting points, while giant covalent structures (diamond, graphite, SiO₂) have very high melting points.
化学键使原子达到稳定外层电子结构，通常为 8 电子（八隅律）。离子键涉及电子从金属转移到非金属，形成带相反电荷的离子，凭借强静电引力相互结合。离子化合物熔点高，在熔融或溶解状态下能导电。共价键在非金属原子间形成，它们共享电子对；简单分子物质（如 CO₂、H₂O）熔点低，而巨型共价结构（金刚石、石墨、SiO₂）熔点极高。
6. Stoichiometry and Moles | 化学计量与摩尔
t of amount of substance, defined as the amount containing 6.02 × 10²³ particles (Avogadro' relative formula mass (Mr) in grams. The formula to relate mass, moles and molar mass is:
moles = mass (g) / molar mass (g/mol)
For gases, the volume of one mole at room temperature and pressure (rtp) is 24 dm³. Using balanced equations, chemists can calculate the masses of reactants and products, as well as the volumes of gases involved in a reaction.
摩尔是物质的量的单位，定义为包含 6.02 × 10²³ 个粒子的物质的量（阿伏伽德罗常数）。任何物质 1 摩尔的质量等于其相对式量（Mr）以克为单位。质量、摩尔与摩尔质量之间的关系为：摩尔数 = 质量 (g) / 摩尔质量 (g/mol)。对于气体，1 摩尔在室温常压（rtp）下的体积为 24 dm³。通过配平的方程式，化学家可以计算反应物与生成物的质量以及涉及的气体体积。
Empirical formula is the simplest whole-number ratio of atoms in a compound; molecular formula shows the actual number of atoms of each element in a molecule. Percentage yield and atom economy are important concepts in evaluating the efficiency of chemical reactions, especially in industrial chemistry.
经验式是化合物中原子最简整数比；分子式表示分子中每种元素原子的实际数目。百分产率和原子经济性是评估化学反应效率的重要概念，尤其在工业化学中。
7. Acids, Bases and Salts | 酸、碱与盐
Acids are substances that release hydrogen ions (H⁺) in aqueous solution; they have a pH less than 7 and turn blue litmus red. Bases neutralise acids to form salts and water, and alkalis are soluble bases that release hydroxide ions (OH⁻) in solution. Common strong acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃).
酸是在水溶液中释放出氢离子 (H⁺) 的物质；它们的 pH 小于 7，能使蓝色石蕊试纸变红。碱能中和酸生成盐和水，而碱溶液（可溶性碱）在水中释放氢氧根离子 (OH⁻)。常见的强酸有盐酸 (HCl)、硫酸 (H₂SO₄) 和硝酸 (HNO₃)。
(l). Soluble salts can be prepared by reacting an acid with a metal, a metal oxide or a carbonate. Insoluble salts are made by precipitation reactions. Titration is a quantitative technique used to determine the concentration of an acid or alkali by neutralisation.
酸与碱的反应称为中和反应，其离子方程式为 H⁺(aq) + OH⁻(aq) → H₂O(l)。可溶性盐可通过酸与金属、金属氧化物或碳酸盐的反应制备。不溶性盐则通过沉淀反应制取。滴定是一种利用中和反应测定酸或碱浓度的定量技术。
8. Forces and Motion | 力与运动
Motion can be described using quantities such as distance, displacement, speed, velocity and acceleration. Acceleration is the rate of change of velocity. The key equations of uniformly accelerated motion include:
v = u + at
s = ut + ½at²
where u is initial velocity, v final velocity, a acceleration, t time and s displacement. On a distance–time graph, the gradient gives speed; on a velocity–time graph, the gradient is acceleration and the area under the graph gives displacement.
运动可用距离、位移、速率、速度和加速度等物理量描述。加速度是速度的变化率。匀加速直线运动的关键方程包括：v = u + at 和 s = ut + ½at²，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。在距离—时间图中，斜率表示速率；在速度—时间图中，斜率是加速度，图线下的面积表示位移。
Forces can change the shape, speed or direction of an object. Newton' Earth). Friction, air resistance and tension are common contact forces. When forces on an object are balanced, it remains at rest or moves at constant velocity.
力可以改变物体的形状、速度或方向。牛顿第二定律将力、质量和加速度联系起来：F = m × a。重力是地球引力产生的力，W = m × g（地球上 g ≈ 9.8 m/s² ）。摩擦力、空气阻力和张力是常见的接触力。当物体受到的力平衡时，它将保持静止或匀速直线运动。
9. Energy, Work and Power | 能量、功与功率
f energy states that energy cannot be created or destroyed, only transferred, stored or transformed. Work is done when a force moves an object in the direction of the force: work (J) = force (N) × distance (m).
能量有多种形式，包括动能、重力势能、热能、化学能和核能。能量守恒定律指出，能量不能被创造或消灭，只能被转移、储存或转化。当一个力使物体沿力的方向移动时，就对物体做了功：功 (J) = 力 (N) × 距离 (m)。
sured in watts (J/s). Efficiency is the ratio of useful output energy to total input energy, often expressed as a percentage. Sankey diagrams provide a visual representation of energy transfers, with the width of arrows representing the amount of energy.
功率是做功或转移能量的速率：P = E / t 或 P = W / t，单位为瓦特 (J/s)。效率是有用输出能量与总输入能量之比，通常以百分比表示。桑基图以箭头的宽度表示能量的大小，直观地展现能量传递过程。
10. Waves and the Electromagnetic Spectrum | 波与电磁波谱
Waves transfer energy without transferring matter. Transverse waves, such as light and water waves, oscillate perpendicular to the direction of energy transfer; longitudinal waves, such as sound, oscillate parallel to it. The wave equation relates speed (v), frequency (f) and wavelength (λ):
v = f × λ
Waves can be reflected, refracted and diffracted. Reflection obeys the law: angle of incidence equals angle of reflection. Refraction occurs when a wave changes speed as it crosses a boundary between two media of different densities, causing a change in direction.
波传递能量而不传递物质。横波（如光波和水波）的振动方向与能量传递方向垂直；纵波（如声波）的振动方向与传递方向平行。波速方程将波速 (v)、频率 (f) 和波长 (λ) 联系起来：v = f × λ。波可以发生反射、折射和衍射。反射遵循定律：入射角等于反射角。当波穿越两种不同密度介质的界面时速度发生改变，从而产生折射，并改变传播方向。
quency and decreasing wavelength: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. Each region has distinct properties and practical applications, from communication (radio) to medical imaging (X-rays).
电磁波谱是一组横波，在真空中均以相同速度传播 (3.0 × 10⁸ m/s)。按频率递增、波长递减的顺序排列为：无线电波、微波、红外线、可见光、紫外线、X 射线和伽马射线。每一波段都有独特的性质和实际应用，从通信（无线电波）到医学成像（X 射线）。
11. Electricity and Circuits | 电与电路
voltage) is the energy transferred per unit charge and is measured in volts (V). Resistance, measured in ohms (Ω), opposes the flow of current. Ohm's law states: V = I × R, where I is current and R resistance.
电流是电荷的流动，以安培 (A) 为单位。在金属导线中，电荷载体是自由电子。电势差（电压）是单位电荷转移的能量，以伏特 (V) 为单位。电阻以欧姆 (Ω) 为单位，阻碍电流的流动。欧姆定律表示为：V = I × R，其中 I 为电流，R 为电阻。
oltage across each branch is the same, while the total current is the sum of branch currents. Power in an electrical circuit is given by P = I × V or P = I² × R. Electrical energy transferred can be calculated using E = I × V × t.
在串联电路中，各点电流相同，总电阻等于各电阻之和。在并联电路中，各支路两端电压相同，总电流等于各支路电流之和。电路中的功率由 P = I × V 或 P = I² × R 给出。电能转移可用 E = I × V × t 计算。
12. Radioactivity and Nuclear Physics | 放射性及核物理
Some atomic nuclei are unstable and emit radiation to become more stable. There are three main types of radiation: alpha particles (helium nuclei, 2 protons + 2 neutrons), beta particles (high-speed electrons) and gamma rays (electromagnetic waves of very high frequency). Their penetrating power increases from alpha (stopped by paper) to beta (stopped by a few mm of aluminium) to gamma (reduced by thick lead).
某些原子核不稳定，会通过辐射以变得更加稳定。辐射主要分为三种：α 粒子（氦核，2 个质子 + 2 个中子）、β 粒子（高速电子）和 γ 射线（极高频率的电磁波）。它们的穿透能力依次增强：α 射线能被纸张阻挡，β 射线可被几毫米铝板阻挡，γ 射线则需要厚铅板才能削弱。
The half-life is the time taken for half the radioactive nuclei in a sample to decay. Radioactivity has practical uses including radiotherapy for cancer, sterilisation of medical equipment, carbon dating and smoke detectors. Nuclear fission involves the splitting of a heavy nucleus (e.g. uranium-235) into two smaller nuclei, releasing a large amount of energy; fusion is the joining of light nuclei (e.g. hydrogen isotopes) to form a heavier nucleus, which powers the Sun.
半衰期是样本中一半放射性原子核发生衰变所需的时间。放射性有多种实际用途，包括癌症放射治疗、医疗器械灭菌、碳年代测定和烟雾探测器。核裂变是重原子核（如铀-235）分裂成两个较小原子核的过程，释放巨大能量；核聚变是轻核（如氢的同位素）结合成较重原子核的过程，为太阳提供能量。
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