📚 IGCSE OCR Science: Last-Minute Revision Notes | IGCSE OCR 科学：考前冲刺笔记
This revision guide condenses key concepts from Biology, Chemistry, and Physics for the OCR GCSE Science specifications, often used in an IGCSE-style curriculum. Use these bite-sized reminders to secure those final marks—whether you are taking Combined Science or the separate sciences. Every statement is matched with its Chinese equivalent to strengthen dual-language understanding.
本复习指南浓缩了OCR GCSE科学（常用于IGCSE课程体系）中生物、化学和物理的核心概念。用这些精炼的知识要点来锁定最后的关键分数——无论你参加的是综合科学还是单科科学。每个陈述都配有中文对照，以加强双语理解。
1. Cell Structure and Function | 细胞结构与功能
All living organisms are built from cells. Eukaryotes (animals, plants, fungi) possess a nucleus, cytoplasm, cell membrane, and organelles such as mitochondria and ribosomes. Plant cells also have a cellulose cell wall, a permanent vacuole, and chloroplasts for photosynthesis.
所有生物体都由细胞构成。真核生物（动物、植物、真菌）拥有细胞核、细胞质、细胞膜以及线粒体和核糖体等细胞器。植物细胞还有纤维素细胞壁、一个中央液泡和用于光合作用的叶绿体。
lasmids. Cell size is measured in micrometres, and magnification = image size ÷ real size.
原核生物（细菌）没有细胞核；它们的遗传物质是一团漂浮在细胞质中的环状DNA。有些细菌含有质粒。细胞大小以微米为单位测量，放大倍数 = 图像尺寸 ÷ 实际尺寸。
Specialised cells show adaptations for their function: sperm cells have a tail and many mitochondria, root hair cells have a large surface area for water uptake, xylem vessels are dead hollow tubes strengthened by lignin.
特化细胞表现出与其功能相适应的结构：精细胞有尾巴和大量线粒体，根毛细胞有巨大的表面积以吸收水分，木质部导管是由木质素加固的死细胞构成的中空管。
2. Photosynthesis and Respiration | 光合作用与呼吸作用
en (in the presence of light and chlorophyll). It is endothermic, trapping energy in glucose.
光合作用是植物和藻类利用光能，由二氧化碳和水合成葡萄糖的过程。其文字方程式：二氧化碳 + 水 → 葡萄糖 + 氧气（在光能和叶绿体参与下）。这是一个吸热反应，将能量储存在葡萄糖中。
arbon dioxide + water (+ energy). Anaerobic respiration in animals produces lactic acid; in yeast it produces ethanol and carbon dioxide (fermentation).
有氧呼吸在活细胞的线粒体中从葡萄糖释放能量：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。动物缺氧呼吸产生乳酸；酵母缺氧呼吸则产生乙醇和二氧化碳（发酵）。
Limiting factors of photosynthesis are light intensity, carbon dioxide concentration, and temperature. Graphs plateau when another factor becomes limiting. Greenhouse experiments optimise these for crop growth.
光合作用的限制因子是光照强度、二氧化碳浓度和温度。当另一个因子变为限制因素时，曲线图会出现平台期。温室实验通过优化这些因素来促进作物生长。
3. The Periodic Table and Bonding | 元素周期表与化学键
Elements are arranged in the Periodic Table in order of increasing atomic number. Groups show similar chemical properties. Group 1 (alkali metals) are extremely reactive; reactivity increases down the group. Group 7 (halogens) become less reactive down the group. Group 0 (noble gases) are inert.
元素按原子序数递增的顺序排在元素周期表中。同族元素具有相似的化学性质。第1族（碱金属）非常活泼，活泼性从上到下增强。第7族（卤素）活泼性从上到下减弱。第0族（惰性气体）化学性质不活泼。
Ionic bonding occurs between metals and non-metals, transferring electrons to form oppositely charged ions that attract in a giant lattice. Covalent bonding shares electron pairs between non-metals, forming molecules or giant covalent structures like diamond and SiO₂.
离子键形成于金属与非金属之间，通过电子转移形成带相反电荷的离子，并在巨型晶格中相互吸引。共价键是非金属之间共享电子对，形成分子或巨型共价结构，如金刚石和二氧化硅。
Metallic bonding features positive metal ions in a sea of delocalised electrons, explaining malleability and electrical conductivity. State symbols (s), (l), (g), (aq) are used in balanced equations.
金属键由正金属离子和离域电子海构成，这解释了金属的延展性和导电性。配平方程式中使用状态符号 (s)、(l)、(g)、(aq)。
4. Quantitative Chemistry | 定量化学
n a formula unit. The mole is the amount of substance that contains 6.02 × 10²³ particles.
相对原子质量（Aᵣ）是一个原子的加权平均质量与碳-12原子质量的1/12相比的比值。相对式量（Mᵣ）是化学式中各原子Aᵣ之和。摩尔是含有6.02 × 10²³个微粒的物质的数量。
Mass (g) = moles × Mᵣ. Percentage yield = (actual yield ÷ theoretical yield) × 100%. Atom economy = (mass of desired product ÷ total mass of reactants) × 100%. High atom economy reduces waste.
质量（克）= 摩尔数 × 相对式量。产率百分比 =（实际产量 ÷ 理论产量）× 100%。原子经济性 =（目标产物质量 ÷ 反应物总质量）× 100%。高原子经济性减少废物。
Molar concentrations (mol/dm³) are linked by the equation concentration = moles ÷ volume.
浓度（克/立方分米）= 溶质质量（克）÷ 体积（立方分米）。滴定使用指示剂来找到准确的中和体积。摩尔浓度（摩尔/立方分米）的关系式为：浓度 = 摩尔数 ÷ 体积。
5. Energy Changes and Rates of Reaction | 能量变化与反应速率
Exothermic reactions release energy to the surroundings, raising temperature (e.g., combustion, neutralisation). Endothermic reactions absorb energy, lowering temperature (e.g., thermal decomposition, photosynthesis). Bond breaking is endothermic; bond making is exothermic.
放热反应向周围环境释放能量，使温度升高（如燃烧、中和）。吸热反应从周围吸收能量，使温度降低（如热分解、光合作用）。断裂化学键是吸热的；形成化学键是放热的。
Rate of reaction measures how quickly reactants become products. It can be followed by measuring gas volume, mass loss, or colour change. Collision theory: particles must collide with energy equal to or greater than the activation energy for a reaction to occur.
反应速率衡量反应物转变为产物的快慢。可以通过测量气体体积、质量损失或颜色变化来跟踪。碰撞理论：粒子必须以等于或大于活化能的能量碰撞，反应才会发生。
Factors increasing rate: higher temperature (particles move faster), higher concentration/pressure (more particles per volume), larger surface area (more exposed particles), and catalysts (lower activation energy).
加快反应速率的因素：升高温度（粒子运动更快），增大浓度/压强（单位体积粒子数增多），增大表面积（暴露更多粒子），以及使用催化剂（降低活化能）。
6. Forces and Motion | 力与运动
On a distance-time graph, a straight line implies constant speed; a horizontal line means stationary. The gradient of a velocity-time graph gives acceleration; area under gives distance.
速率（米/秒）= 距离 ÷ 时间。速度是带有方向的速率。加速度 = 速度变化量 ÷ 时间。在距离−时间图上，直线表示匀速；水平线表示静止。速度−时间图的斜率表示加速度；图下面积表示距离。
Newton' ct stays at rest or moves at constant velocity unless a resultant force acts on it. Newton' ation (m/s²), F = ma. Inertia is the tendency of an object to resist change in its motion.
牛顿第一定律：物体将保持静止或匀速直线运动状态，除非受到合外力的作用。牛顿第二定律：力（牛）= 质量（千克）× 加速度（米/秒²），F = ma。惯性是物体抵抗改变运动状态的倾向。
istance + braking distance, affected by speed, distractions, alcohol, and road conditions.
合外力导致加速。当重力等于空气阻力时，物体会达到终末速度。停车距离 = 思考距离 + 刹车距离，受车速、注意力分散、酒精和道路状况的影响。
7. Waves and the Electromagnetic Spectrum | 波与电磁波谱
Waves transfer energy without transferring matter. Transverse waves oscillate perpendicular to direction of travel (e.g., water waves, EM waves). Longitudinal waves oscillate parallel to direction of travel (e.g., sound waves, showing compressions and rarefactions).
波传播能量而不传递物质。横波的振动方向垂直于传播方向（如水波、电磁波）。纵波的振动方向平行于传播方向（如声波，表现为压缩和稀疏）。
frared, visible, ultraviolet, X-rays, gamma rays. All travel at 3.0 × 10⁸ m/s in a vacuum.
波速（米/秒）= 频率（赫兹）× 波长（米）。振幅与能量有关。电磁波谱按频率增大的顺序为：无线电波、微波、红外线、可见光、紫外线、X射线、γ射线。所有电磁波在真空中以3.0 × 10⁸ 米/秒传播。
ction occurs when waves change speed at a boundary, bending towards the normal if slowing down. Sound waves cannot travel through a vacuum.
反射遵循定律：入射角等于反射角。当波在边界处改变速度时发生折射，若减速则向法线偏折。声波不能在真空中传播。
8. Electricity and Circuits | 电与电路
olts) is the energy transferred per unit charge. Resistance (R, ohms) opposes current. Ohm's law: V = I × R, applicable at constant temperature.
电流（I，安培）是电荷流动的速率。电位差（V，伏特）是每单位电荷转移的能量。电阻（R，欧姆）阻碍电流。欧姆定律：V = I × R，在温度恒定时适用。
Series circuits: current is the same everywhere, total voltage is shared, total resistance adds up. Parallel circuits: current splits and recombines, each branch gets full supply voltage, total resistance is less than the smallest individual resistor.
串联电路：电流处处相等，总电压被各元件分配，总电阻为各电阻之和。并联电路：电流分叉后汇合，各支路获得全部电源电压，总电阻小于任一单独电阻。
AC/DC: mains electricity is alternating current (50 Hz, ~ d (J) ÷ time (s), or P = I × V. Fuses and circuit breakers protect circuits from overload.
交流/直流：市电是交流电（50 Hz，约230伏）。直流电单向流动。功率（瓦）= 转移的能量（焦）÷ 时间（秒），或 P = I × V。保险丝和断路器保护电路免于过载。
9. Homeostasis and Hormones | 稳态与激素
Homeostasis maintains a stable internal environment. The nervous system uses electrical impulses for fast responses; the endocrine system uses hormones secreted into the blood for slower, longer-lasting control. Insulin lowers blood glucose by enhancing uptake and glycogen storage.
稳态维持稳定的内部环境。神经系统利用电脉冲作出快速反应；内分泌系统通过将激素分泌到血液中实现较慢但持久的调控。胰岛素通过促进葡萄糖吸收和糖原储存来降低血糖。
Glucagon raises blood glucose by breaking down glycogen. Type 1 diabetes is due to insufficient insulin; Type 2 develops when cells become resistant to insulin. Temperature regulation involves sweating, shivering, and vasodilation/vasoconstriction.
胰高血糖素通过分解糖原来升高血糖。1型糖尿病由胰岛素不足引起；2型糖尿病因细胞对胰岛素产生抵抗而发展。体温调节涉及出汗、颤抖以及血管舒张/收缩。
Hormones also control reproduction: FSH stimulates egg maturation, LH triggers ovulation, oestrogen and progesterone regulate the menstrual cycle. Contraceptive pills and fertility drugs exploit these interactions.
激素还控制生殖：促卵泡激素（FSH）促进卵子成熟，黄体生成素（LH）触发排卵，雌激素和孕激素调控月经周期。避孕药和促生育药物利用这些相互作用。
10. Cracking the Exam: Command Words and Practical Skills | 突破考试：指令词与实验技能
'State' means give a simple answer without explanation. 'Describe' requires a step-by-step account of what happens (trends, patterns). 'Explain' asks for scientific reasons—use 'because' and link cause to effect. 'Evaluate' means weigh up pros and cons using data and reach a conclusion.
'State' 指给出简单答案，无需解释。'Describe' 要求逐步叙述发生了什么（趋势、模式）。'Explain' 要求给出科学原因——使用'因为'并将原因与结果联系起来。'Evaluate' 意味着利用数据权衡利弊并得出结论。
When plotting graphs, label axes with quantity and unit, use sharp pencil points, draw a best-fit line if appropriate, and read scales correctly. In a six-mark question, structure your answer in logical steps and use correct scientific terminology.
绘图时，坐标轴标出物理量和单位，用削尖的铅笔，必要时画最佳拟合线，并且准确读刻度。在六分题中，按逻辑步骤组织答案并使用正确的科学术语。
Key practicals: investigate factors affecting enzyme activity, measure the effect of pH on reaction rate, use a ripple tank to observe wave properties, determine the resistivity of a wire, and prepare a soluble salt. Always identify independent, dependent, and control variables.
关键实验：探究影响酶活性的因素，测量pH对反应速率的影响，使用波纹槽观察波的性质，测定金属丝的电阻率，以及制备可溶性盐。始终要明确自变量、因变量和控制变量。
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