📚 IB OCR Science: Final Revision Outline | IB OCR 科学：期末复习提纲
This final revision outline is designed to help students consolidate key concepts for IB and OCR science examinations. Covering the core disciplines of biology, chemistry and physics, the guide breaks down the most important topics into concise, bilingual summaries. Each section pairs an English explanation with its Chinese counterpart, ensuring you grasp both technical terminology and underlying principles. Whether you are refreshing your memory on cell structure, practising mole calculations or reviewing Newton’s laws, this resource provides a structured walkthrough of the syllabus essentials. Use it alongside your notes and past papers to build confidence ahead of exam day.
这份期末复习提纲旨在帮助学生巩固 IB 和 OCR 科学考试的核心概念。提纲涵盖生物学、化学和物理学的基础学科，将最重要的主题分解为简洁的双语摘要。每个部分先提供英文解释，再配以对应的中文内容，确保你既能掌握专业术语，又能理解背后的原理。无论你是在重温细胞结构、练习摩尔计算，还是复习牛顿定律，这份资料都能带你系统地回顾课程大纲的重点。结合你的笔记和历年真题使用，能够帮助你在考试前树立信心。
1. Scientific Method | 科学方法
A controlled experiment tests a hypothesis by changing only one independent variable while keeping all other variables constant. The dependent variable is measured, and control groups are used for comparison. Reliable results require repeated trials and careful recording of observations.
对照实验通过只改变一个自变量而保持其他变量不变的方式来检验假设。因变量被测量，并采用对照组进行对比。要获得可靠的结果，需要反复试验并仔细记录观察结果。
Data should be presented in clearly labelled tables and graphs, with the independent variable on the x-axis. Trends or patterns are then analysed, and conclusions must refer directly to the experimental evidence. Any systematic or random errors should be discussed when evaluating the method.
数据应该用清晰标注的表格和图形展示，自变量通常放在 x 轴。然后分析趋势或规律，结论必须直接引用实验证据。在评估实验方法时还应讨论系统误差和随机误差。
2. Cell Biology | 细胞生物学
All living organisms are made of cells, which are the basic structural and functional units of life. Eukaryotic cells, such as those of plants and animals, contain membrane-bound organelles including a nucleus, mitochondria and ribosomes, whereas prokaryotic cells lack a nucleus.
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。植物和动物等真核细胞含有具膜细胞器，包括细胞核、线粒体和核糖体，而原核细胞没有细胞核。
| Cell type 细胞类型 | Key features 主要特征 |
| Animal cell 动物细胞 | Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes |
| Plant cell 植物细胞 | All of the above plus cell wall, chloroplasts, permanent vacuole |
| Bacterial cell 细菌细胞 | No nucleus; single loop of DNA, plasmid, cell wall, cytoplasm, ribosomes |
Substances move across cell membranes by diffusion, osmosis and active transport. Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration. Osmosis is the diffusion of water through a partially permeable membrane, while active transport requires energy to move substances against the concentration gradient.
物质通过扩散、渗透和主动运输穿过细胞膜。扩散是粒子从高浓度区域向低浓度区域的净运动。渗透是水分子通过部分透性膜的扩散，而主动运输需要能量将物质逆浓度梯度移动。
3. Kinematics and Forces | 运动学与力
Motion is described using quantities such as speed, velocity and acceleration. Speed is a scalar quantity, whereas velocity includes direction. Acceleration is the rate of change of velocity. The key equation for constant acceleration is:
运动用速度、速率和加速度等量来描述。速率是标量，而速度含有方向。加速度是速度的变化率。匀加速运动的关键方程是：
v = u + a t
Forces are pushes or pulls that can change an object’s motion or shape. Newton’s second law states that the net force acting on an object is equal to its mass multiplied by its acceleration:
力是能够改变物体运动状态或形状的推或拉。牛顿第二定律指出，作用在物体上的合力等于物体的质量乘以加速度：
F = m a
Common forces include weight (mass × gravitational field strength), friction, tension and normal contact force. On a distance–time graph, the gradient gives speed; on a velocity–time graph, the gradient gives acceleration and the area under the graph gives displacement.
常见的力包括重力（质量×重力场强度）、摩擦力、张力和法向接触力。在距离–时间图上，斜率表示速率；在速度–时间图上，斜率表示加速度，面积表示位移。
4. Chemical Reactions | 化学反应
In a chemical reaction, atoms are rearranged to form new substances, but no atoms are created or destroyed. This is the principle of conservation of mass. Word equations and balanced symbol equations show the reactants and products. For example, the combustion of methane is:
在化学反应中，原子重新排列形成新物质，但原子没有产生或消失。这就是质量守恒定律。文字方程式和平衡的符号方程式表示反应物与生成物。例如，甲烷的燃烧表示为：
CH₄ + 2O₂ → CO₂ + 2H₂O
Rates of reaction can be affected by temperature, concentration, surface area and the presence of a catalyst. Increasing temperature gives particles more kinetic energy, so collisions are more frequent and energetic. Catalysts lower the activation energy and are not used up in the reaction.
反应速率受温度、浓度、表面积和催化剂的影响。升高温度使粒子动能增加，因此碰撞更频繁、更剧烈。催化剂能降低活化能，且在反应中不被消耗。
Important types of reaction include neutralisation (acid + base → salt + water), redox reactions (in which electrons are transferred), and precipitation reactions. Exothermic reactions release energy to the surroundings, while endothermic reactions absorb energy.
重要的反应类型包括中和反应（酸 + 碱 → 盐 + 水）、氧化还原反应（涉及电子转移）和沉淀反应。放热反应向环境释放能量，吸热反应则吸收能量。
5. Waves and Radiation | 波与辐射
Waves transfer energy without transferring matter. Transverse waves (e.g. light, water waves) have oscillations perpendicular to the direction of energy transfer, whereas longitudinal waves (e.g. sound) have oscillations parallel to the direction of energy transfer. All waves obey the wave equation:
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，而纵波（如声波）的振动方向与能量传递方向平行。所有波都遵循波动方程：
v = f λ
The electromagnetic spectrum, in order of increasing wavelength, includes gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves and radio waves. All EM waves travel at the same speed in a vacuum (3.0 × 10⁸ m/s). Different wavelengths are used for communication, medical imaging and heating.
电磁波谱按波长递增顺序包括伽马射线、X 射线、紫外线、可见光、红外线、微波和无线电波。所有电磁波在真空中传播速度相同（3.0×10⁸ m/s）。不同波长用于通信、医学成像和加热。
Radioactive decay is a random process in which an unstable nucleus emits alpha particles, beta particles or gamma rays. Half-life is the time taken for half of the radioactive nuclei in a sample to decay. Background radiation comes from natural and artificial sources.
放射性衰变是一种随机过程，不稳定的原子核发出 α 粒子、β 粒子或 γ 射线。半衰期是样本中一半放射性原子核发生衰变所需的时间。背景辐射来自天然和人工来源。
6. Genetics and Evolution | 遗传与进化
DNA is a double helix molecule carrying genetic information. A gene is a section of DNA that codes for a particular protein. Alleles are different forms of a gene. Dominant alleles mask the effect of recessive alleles unless two recessive alleles are present.
DNA 是携带遗传信息的双螺旋分子。基因是 DNA 上编码特定蛋白质的片段。等位基因是基因的不同形式。显性等位基因会掩盖隐性等位基因的效应，除非存在两个隐性等位基因。
In sexual reproduction, gametes (sperm and egg) are produced by meiosis, resulting in four genetically different haploid cells. Fertilisation restores the diploid number. Variation in a population arises from mutations, meiosis and random fertilisation. Natural selection acts on this variation: individuals with advantageous traits are more likely to survive and reproduce, passing the trait to offspring.
在有性生殖中，配子（精子和卵子）通过减数分裂产生，形成四个基因不同的单倍体细胞。受精恢复双倍体数目。种群中的变异源于突变、减数分裂和随机受精。自然选择作用于这些变异：具有有利性状的个体更可能存活和繁殖，并将性状传递给后代。
7. Electricity and Magnetism | 电与磁
Electric current is the flow of charge. In metals, the charge carriers are free electrons. Current (I) is measured in amperes (A) and voltage (V) in volts. Resistance (R) is measured in ohms (Ω). Ohm’s law states:
电流是电荷的流动。在金属中，电荷载流子是自由电子。电流（I）以安培（A）为单位，电压（V）以伏特为单位，电阻（R）以欧姆（Ω）为单位。欧姆定律表示为：
V = I R
In a series circuit, the current is the same everywhere, but the total voltage is shared across components. In a parallel circuit, the voltage across each branch is the same, but the currents add up. Power (P) is the rate of energy transfer and can be calculated using:
在串联电路中，各处电流相同，但总电压在各元件间分配。在并联电路中，各支路电压相同，但电流相加。功率（P）是能量传递的速率，可用公式计算：
P = I V
Electromagnetism describes how a current-carrying wire produces a magnetic field. An electromagnet can be made by coiling the wire around an iron core. The motor effect occurs when a current-carrying conductor is placed in a magnetic field, producing a force. This principle is used in electric motors.
电磁学描述了载流导线如何产生磁场。将导线缠绕在铁芯上可制成电磁铁。当载流导体置于磁场中时会产生一个力，称为电动机效应，该原理被应用于电动机中。
8. Ecology and Environment | 生态与环境
An ecosystem consists of a community of organisms interacting with their physical environment. Producers (plants) convert light energy into chemical energy through photosynthesis. Consumers obtain energy by eating other organisms. Decomposers break down dead material, recycling nutrients.
生态系统由生物群落与其物理环境相互作用构成。生产者（植物）通过光合作用将光能转化为化学能。消费者通过摄食其他生物获取能量。分解者分解死去的物质，使养分得以循环。
Food chains show linear feeding relationships, while food webs represent interconnected chains. Energy is lost at each trophic level as heat and waste, so the number of organisms decreases at higher levels. Pyramids of biomass illustrate this energy transfer.
食物链展示线性的摄食关系，食物网则表示相互关联的链条。能量在每一营养级以热量和废物的形式损失，因此高营养级的生物数量较少。生物量金字塔体现了这种能量传递。
Human activities, such as deforestation, burning fossil fuels and intensive farming, can disrupt ecosystems. They contribute to rising carbon dioxide levels, global warming and loss of biodiversity. Conservation efforts, sustainable resource use and recycling help reduce these impacts.
砍伐森林、燃烧化石燃料和集约农业等人类活动会扰乱生态系统。这些活动导致二氧化碳浓度上升、全球变暖和生物多样性丧失。保护行动、资源的可持续利用和回收有助于减少这些影响。
9. Structure of Matter | 物质结构
The kinetic particle model explains the properties of solids, liquids and gases. In solids, particles vibrate in fixed positions; in liquids, they move around but stay close together; in gases, they move rapidly in random directions. Changes of state involve energy transfer without a change in temperature at the melting or boiling point.
分子动理论模型解释了固体、液体和气体的性质。固体中粒子在固定位置振动；液体中粒子能够移动但彼此靠近；气体中粒子快速、随机地向各个方向运动。物态变化涉及能量转移，但在熔点或沸点时温度保持不变。
Atoms consist of a central nucleus containing protons and neutrons, surrounded by electrons in shells. The atomic (proton) number determines the element, while the mass number is the sum of protons and neutrons. Isotopes are atoms of the same element with different numbers of neutrons.
原子由包含质子和中子的中心原子核以及核外分层排布的电子组成。原子序数（质子数）决定元素种类，而质量数是质子与中子数之和。同位素是具有相同质子数但中子数不同的同种元素原子。
Elements are arranged in the Periodic Table in order of increasing atomic number. Groups contain elements with similar chemical properties because they have the same number of electrons in their outer shell. The noble gases (Group 18) are unreactive due to a full outer shell.
元素按原子序数递增的顺序排列在元素周期表中。同一族的元素因最外层电子数相同而具有相似的化学性质。稀有气体（第18族）因最外层电子已满而不活泼。
10. Energy and Power | 能量与功率
Energy exists in different forms: kinetic, gravitational potential, thermal, chemical, elastic, nuclear and electromagnetic. The law of conservation of energy states that energy cannot be created or destroyed, only transferred or stored. Sankey diagrams visually represent energy transfers.
能量有多种形式：动能、重力势能、热能、化学能、弹性势能、核能和电磁能。能量守恒定律指出，能量不能被创造或消灭，只能被传递或储存。桑基图直观地表示能量的传递。
Work done (energy transferred) by a force is given by the product of force and distance moved in the direction of the force. Efficiency is the ratio of useful output energy to total input energy, usually expressed as a percentage:
力所做的功（能量转移）等于力与沿力的方向移动距离的乘积。效率是有用输出能量与总输入能量之比，通常用百分数表示：
Efficiency = (Useful output / Total input) × 100%
Renewable energy resources (solar, wind, tidal, hydroelectric, geothermal) can be replenished, while non-renewables (coal, oil, natural gas) are finite and release carbon dioxide when burned. Choosing an energy source involves balancing reliability, cost and environmental impact.
可再生能源（太阳能、风能、潮汐能、水力发电、地热能）能够再生，而非可再生能源（煤、石油、天然气）是有限的，燃烧时会释放二氧化碳。选择能源需要在可靠性、成本和环境影响之间取得平衡。
11. Experimental Skills | 实验技能
Accurate measurements rely on using the correct apparatus, such as measuring cylinders for volume, stopwatches for time and balances for mass. It is essential to read instruments at eye level to avoid parallax error and to repeat measurements to identify anomalies.
精确的测量依赖正确的仪器使用，例如用量筒测量体积、用秒表测量时间、用天平测量质量。必须平视读数以避免视差，并重复测量以识别异常值。
When plotting graphs, choose appropriate scales, label axes with units and draw a line of best fit. The slope of a straight line can be calculated using the gradient formula. Describe the relationship between variables in terms of proportionality (e.g., directly proportional, inversely proportional).
绘制图表时，应选择合适的比例，标注轴和单位，并画出一条最佳拟合线。直线的斜率可以用梯度公式计算。用比例关系（如正比、反比）来描述变量之间的关系。
Evaluating an experiment involves identifying sources of error, suggesting realistic improvements and discussing whether the results are reproducible. A conclusion should be supported by the data and linked back to the original hypothesis.
评价实验包括识别误差来源、提出切实可行的改进方案，并讨论结果是否可复现。结论应以数据为依据，并回扣最初的假设。
12. Final Exam Tips | 终极考试技巧
Begin your revision by breaking the syllabus into smaller topics and creating a realistic timetable. Use active recall techniques – test yourself rather than just rereading notes. Past paper questions are invaluable: they familiarise you with the command terms (describe, explain, evaluate) and the style of marking.
开始复习前，先把课程大纲切分为更小的主题，并制订切实可行的时间表。运用主动回忆的技巧——自我测试而不仅限于反复阅读笔记。历年真题极为宝贵：它们能让你熟悉指令词（描述、解释、评价）和评分风格。
During the exam, read each question carefully and note the number of marks allocated – this indicates the depth required. For calculations, show all working steps and include units in the final answer. In longer-answer questions, structure your response logically, linking ideas and using scientific terminology accurately.
考试时，仔细阅读每一道题，注意题目所分配的分数——这提示了答案所需的详略程度。对于计算题，要展示全部步骤，并在最终答案中写上单位。在回答较长的问题时，要逻辑清晰地进行论述，串联观点，并准确使用科学术语。
Manage your time effectively: allocate roughly one minute per mark, leaving time to check your answers. Stay calm and focus on demonstrating your understanding. Remember that revision is about reinforcing what you already know, not learning everything from scratch.
合理分配时间：大致按每分钟一分的速度答题，并留出检查的时间。保持冷静，专注于展示你已掌握的知识。请记住，复习是强化已知内容，而非从零开始学习一切。
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