📚 IB & Edexcel Science: High-Frequency Topic Summary | IB 与 Edexcel 科学：高频考点总结
Whether you are preparing for IB MYP Sciences, IB Diploma Biology/Chemistry/Physics, or Edexcel IGCSE/IAL Science, certain key concepts appear again and again across specifications. This article summarises the high-frequency topics that bridge both curricula — from cell biology and atomic structure to forces and genetics — helping you focus your revision on what truly matters. We break down each concept into bite‑sized, bilingual explanations, pairing every English point with its Chinese equivalent so you can learn terminology and content simultaneously.
无论你正在备考 IB MYP 科学、IB 文凭生物/化学/物理，还是 Edexcel IGCSE/IAL 科学，某些核心概念都会在考纲中反复出现。本文总结了横跨这两大课程体系的高频考点——从细胞生物学、原子结构到力和遗传学——帮助你聚焦真正重要的内容。我们将每个概念拆解为精炼的双语解释，每个英文要点紧跟着对应的中文要点，让你同步掌握术语与知识。
1. Cell Structure and Function | 细胞结构与功能
All living organisms are composed of cells, which can be prokaryotic (no nucleus, e.g. bacteria) or eukaryotic (membrane‑bound nucleus, e.g. animal and plant cells). Key organelles include the nucleus, mitochondria, ribosomes, and in plants, chloroplasts and a permanent vacuole.
所有生物体均由细胞构成，细胞可分为原核细胞（无细胞核，如细菌）和真核细胞（有膜包被的细胞核，如动物和植物细胞）。重要细胞器包括细胞核、线粒体、核糖体，植物细胞还含有叶绿体和中央大液泡。
Under a light microscope, you can observe the cell wall, cytoplasm and nucleus; magnification = eyepiece lens magnification × objective lens magnification. Electron microscopes have much higher resolving power, revealing internal structures like cristae in mitochondria.
在光学显微镜下，你可以观察到细胞壁、细胞质和细胞核；放大倍数 = 目镜放大倍数 × 物镜放大倍数。电子显微镜具有更高的分辨率，能够显示线粒体内的嵴等内部结构。
Specialised cells (e.g. red blood cells, root hair cells, sperm cells) are adapted to their functions: red blood cells lack a nucleus to carry more haemoglobin, while root hair cells have long extensions to increase surface area for water absorption.
特化细胞（如红细胞、根毛细胞、精子细胞）与其功能相适应：红细胞没有细胞核以便携带更多血红蛋白，而根毛细胞具有长突起以增大水分吸收的表面积。
2. Atomic Structure and the Periodic Table | 原子结构与元素周期表
Atoms consist of protons (positive charge, mass 1), neutrons (neutral, mass 1) and electrons (negative charge, negligible mass). The atomic number = number of protons, and the mass number = protons + neutrons.
原子由质子（带正电，质量1）、中子（不带电，质量1）和电子（带负电，质量可忽略）组成。原子序数 = 质子数，质量数 = 质子数 + 中子数。
Electrons are arranged in shells: 2, 8, 8, … for the first 20 elements. The group number in the periodic table indicates the number of outer‑shell electrons, while the period number gives the number of occupied shells.
电子按电子层排布：前20号元素的排布规律为2、8、8……。周期表中族序数表示最外层电子数，周期序数表示电子层数。
Isotopes are atoms of the same element with different numbers of neutrons (e.g. ¹²C and ¹⁴C). Relative atomic mass accounts for the abundance of each isotope.
同位素是同一元素中中子数不同的原子（如碳‑12与碳‑14）。相对原子质量考虑了各同位素的丰度。
3. Chemical Bonding and Structures | 化学键与结构
Ionic bonding occurs between metals and non‑metals: electrons are transferred, forming positive and negative ions that attract in a giant ionic lattice. Example: sodium chloride (Na⁺ Cl⁻).
离子键发生在金属与非金属之间：电子发生转移，形成正离子和负离子，它们通过静电作用结合成巨大的离子晶格。例如：氯化钠 (Na⁺ Cl⁻)。
Covalent bonding involves sharing of electron pairs between non‑metals. Simple molecular substances (e.g. H₂O, CO₂) have low melting points due to weak intermolecular forces, while giant covalent structures (e.g. diamond, SiO₂) are very hard and have high melting points.
共价键涉及非金属原子之间共享电子对。简单分子物质（如H₂O、CO₂）由于分子间作用力较弱，熔点较低；而巨型共价结构（如金刚石、SiO₂）硬度极大、熔点很高。
Metallic bonding consists of positive metal ions in a ‘sea’ of delocalised electrons. This explains electrical conductivity and malleability of metals.
金属键由金属阳离子和离域电子的“海洋”组成。这解释了金属的导电性和延展性。
4. Forces and Motion | 力与运动
Speed = distance ÷ time. Velocity includes direction. Acceleration = change in velocity ÷ time, measured in m/s². In a distance–time graph, a straight line shows constant speed; a curved line shows acceleration.
速率 = 距离 ÷ 时间。速度包含方向。加速度 = 速度变化量 ÷ 时间，单位为 m/s²。在距离–时间图像中，直线表示匀速，曲线表示加速运动。
Newton’s First Law: an object stays at rest or moves with constant velocity unless a resultant force acts. Newton’s Second Law: F = m × a (resultant force = mass × acceleration).
牛顿第一定律：除非受到合外力，物体将保持静止或匀速直线运动状态。牛顿第二定律：F = m × a（合外力 = 质量 × 加速度）。
Weight = mass × gravitational field strength (g = 9.8 N/kg on Earth). Friction opposes motion. Terminal velocity is reached when weight = air resistance for a falling object.
重量 = 质量 × 重力场强度（地球 g = 9.8 N/kg）。摩擦力阻碍运动。当自由落体所受重力与空气阻力平衡时，物体达到终极速度。
5. Energy Transfers and Resources | 能量转移与资源
Energy can be stored as kinetic, gravitational potential, chemical, elastic, thermal, nuclear, etc. It is transferred via heating, waves, electric current or mechanical work. The unit is the joule (J).
能量可以储存为动能、重力势能、化学能、弹性势能、热能、核能等形式。能量通过加热、波动、电流或机械做功传递，单位为焦耳 (J)。
Efficiency = useful output energy ÷ total input energy × 100%. Sankey diagrams show energy transfers, with arrow widths proportional to energy quantities.
效率 = 有用输出能量 ÷ 总输入能量 × 100%。桑基图以箭头的宽度表示能量流的大小，直观展示能量转移。
Renewable resources include solar, wind, hydroelectric, and biofuels; non‑renewable resources are fossil fuels (coal, oil, gas) and nuclear fuels. Burning fossil fuels releases CO₂, contributing to climate change.
可再生能源包括太阳能、风能、水力和生物燃料；不可再生资源是化石燃料（煤、石油、天然气）和核燃料。燃烧化石燃料会释放二氧化碳，加剧气候变化。
6. Waves and the Electromagnetic Spectrum | 波与电磁波谱
Waves transfer energy without transferring matter. Transverse waves (e.g. light, water ripples) have oscillations perpendicular to wave direction; longitudinal waves (e.g. sound) have oscillations parallel to direction.
波传递能量而不传递物质。横波（如光波、水波）的振动方向与波传播方向垂直；纵波（如声波）的振动方向与传播方向平行。
Wave equation: v = f × λ (wave speed = frequency × wavelength). Period (T) = 1 / f. The electromagnetic spectrum (radio, microwave, infrared, visible, UV, X‑ray, gamma) all travel at 3×10⁸ m/s in a vacuum.
波速公式：v = f × λ（波速 = 频率 × 波长）。周期 T = 1 / f。电磁波谱（无线电波、微波、红外线、可见光、紫外线、X射线、伽马射线）在真空中均以 3×10⁸ m/s 传播。
Reflection follows the law: angle of incidence = angle of reflection. Refraction occurs when waves enter a new medium at an angle, causing a change in speed and direction.
反射遵循定律：入射角 = 反射角。当波倾斜进入新介质时发生折射，波速和方向改变。
7. States of Matter and Changes of State | 物态与状态变化
Matter exists as solid, liquid or gas. In solids, particles vibrate in fixed positions; in liquids, they slide past each other; in gas, they move rapidly and randomly. The kinetic particle model explains these properties.
物质以固态、液态或气态存在。固态中粒子在固定位置振动；液态中粒子相互滑移；气态中粒子快速无规则运动。粒子动力学模型解释了这些性质。
Melting, freezing, boiling, condensation and sublimation are physical changes. Temperature stays constant during a state change because energy is used to overcome inter‑particle forces (latent heat).
熔化、凝固、沸腾、冷凝和升华属于物理变化。状态变化期间温度保持不变，因为能量用于克服粒子间作用力（潜热）。
Diffusion is the net movement of particles from a region of higher concentration to lower concentration, driven by random motion. It is fastest in gases and increases with temperature.
扩散是粒子在随机运动驱动下，从高浓度区域向低浓度区域的净移动。气体中扩散最快，温度升高时扩散速率增加。
8. Genetics and Evolution | 遗传与进化
DNA is a double helix containing four bases: adenine (A), thymine (T), cytosine (C) and guanine (G). A pairs with T, C pairs with G. A gene is a section of DNA that codes for a protein.
DNA 是双螺旋结构，包含四种碱基：腺嘌呤(A)、胸腺嘧啶(T)、胞嘧啶(C)和鸟嘌呤(G)。A与T配对，C与G配对。基因是编码蛋白质的一段 DNA。
Mitosis produces two genetically identical diploid cells for growth and repair; meiosis produces four genetically varied haploid gametes. Sexual reproduction increases genetic variation, while asexual reproduction produces clones.
有丝分裂产生两个遗传物质相同的二倍体细胞，用于生长和修复；减数分裂产生四个遗传物质不同的单倍体配子。有性生殖增加遗传变异，无性生殖产生克隆。
Natural selection: organisms with advantageous alleles survive, reproduce and pass on those alleles. Over generations, this leads to evolution. Evidence includes fossils and antibiotic‑resistant bacteria.
自然选择：具有有利等位基因的生物生存、繁殖并将这些等位基因传递下去。经过多代，这个过程导致进化。化石和抗生素耐药细菌提供了证据。
9. Stoichiometry and the Mole Concept | 化学计量与摩尔概念
The mole is the unit for amount of substance, containing 6.02×10²³ particles. Molar mass (M) in g/mol is numerically equal to the relative formula mass. Amount (mol) = mass (g) ÷ M.
摩尔是物质的量的单位，1 mol 含有 6.02×10²³ 个粒子。摩尔质量 (M) 在数值上等于相对式量，单位为 g/mol。物质的量 (mol) = 质量 (g) ÷ M。
Avogadro’s law: equal volumes of gases at the same temperature and pressure contain equal numbers of moles. Molar volume at r.t.p. is 24 dm³/mol (Edexcel).
阿伏伽德罗定律：同温同压下，相同体积的气体含有相等的物质的量。在室温常压下，摩尔体积为 24 dm³/mol (Edexcel)。
Empirical formula gives the simplest whole‑number ratio of atoms; molecular formula gives the actual number. Using moles, you can calculate reacting masses and percentage yield.
经验式给出原子最简整数比；分子式给出实际原子数。利用物质的量可以计算反应质量和产率。
10. Electricity and Circuits | 电与电路
Current (I) is the rate of flow of charge, measured in amperes (A). Potential difference (V) is the work done per unit charge. Resistance (R) = V ÷ I. Ohm’s law: V = I × R for ohmic conductors at constant temperature.
电流 (I) 是电荷流动的速率，单位为安培 (A)。电势差 (V) 是每单位电荷所做的功。电阻 (R) = V ÷ I。欧姆定律：在恒温下，欧姆导体的 V = I × R。
In series circuits, current is the same everywhere, and total resistance = sum of individual resistances. In parallel circuits, voltage is the same across each branch; total current splits between branches.
串联电路中各处电流相等，总电阻等于各电阻之和。并联电路中各支路两端电压相等，总电流在支路中分流。
Power (P) = I × V. Energy transferred (E) = P × time. Electrical safety includes fuses, circuit breakers and earthing.
功率 P = I × V。电能 E = 功率 × 时间。电气安全措施包括保险丝、断路器和接地保护。
11. Homeostasis and the Nervous System | 稳态与神经系统
Homeostasis is the maintenance of a constant internal environment. Examples: regulation of blood glucose (insulin and glucagon), body temperature (vasodilation, sweating, shivering) and water balance (ADH).
稳态是维持体内环境稳定的过程。例如：血糖调节（胰岛素与胰高血糖素）、体温调节（血管舒张、出汗、颤抖）和水平衡（抗利尿激素）。
The nervous system uses electrical impulses along neurones. A reflex arc involves a sensory neurone, relay neurone in the spinal cord, and motor neurone, enabling rapid responses to stimuli.
神经系统通过神经元中的电冲动传递信号。反射弧涉及感觉神经元、脊髓中的中间神经元和运动神经元，实现对刺激的迅速反应。
Synapses are gaps between neurones where neurotransmitters diffuse across to continue the impulse. Hormones, by contrast, travel in the blood and have slower, longer‑lasting effects.
突触是神经元之间的间隙，神经递质在此扩散以传递冲动。相反，激素通过血液运输，作用较慢但持续时间更长。
12. Acids, Bases and pH | 酸、碱与 pH
Acids are proton (H⁺) donors; bases are proton acceptors. Common acids: HCl, H₂SO₄, HNO₃. Alkalis are soluble bases that release OH⁻ ions in water.
酸是质子 (H⁺) 给予体；碱是质子接受体。常见酸：HCl、H₂SO₄、HNO₃。碱是可溶的碱，在水中释放 OH⁻ 离子。
Neutralisation: acid + base → salt + water. For example, HCl + NaOH → NaCl + H₂O. Titration using an indicator determines the exact volume of acid needed to neutralise a known volume of alkali.
中和反应：酸 + 碱 → 盐 + 水。例如，HCl + NaOH → NaCl + H₂O。利用指示剂进行滴定，可以精确测定中和一定体积碱所需的酸体积。
The pH scale (0–14) measures acidity: pH < 7 is acidic, pH = 7 neutral, pH > 7 alkaline. Strong acids fully dissociate in water, while weak acids partially dissociate.
pH 标度（0–14）衡量酸碱度：pH < 7 为酸性，pH = 7 中性，pH > 7 碱性。强酸在水中完全解离，弱酸则部分解离。
Published by TutorHao | Science Revision Series | aleveler.com
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