IGCSE Edexcel Science Revision: Mastering the Core Concepts | IGCSE Edexcel 科学复习：掌握核心概念

📚 IGCSE Edexcel Science Revision: Mastering the Core Concepts | IGCSE Edexcel 科学复习：掌握核心概念

This revision guide is designed for IGCSE students following the Edexcel Science specification (Double Award or separate sciences). It focuses on the most frequently tested concepts across Biology, Chemistry, and Physics, with clear explanations, key equations, and exam-style reminders. Use this as your structured checklist for final revision.

本复习指南面向学习 Edexcel IGCSE 科学（双奖或分科）的学生，聚焦生物、化学和物理中最常考的核心概念，提供清晰的解释、关键方程式和考试提醒。请将其作为最终复习的结构化清单。

1. Cell Structure and Function | 细胞结构与功能

All living organisms are made of cells. In the IGCSE Edexcel specification, you need to compare animal cells, plant cells, and bacterial cells. Animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes. Plant cells additionally have a cell wall made of cellulose, chloroplasts for photosynthesis, and a permanent vacuole containing cell sap. Bacterial cells lack a nucleus; their genetic material is a single circular DNA molecule in the cytoplasm, and they may have plasmids and a capsule.

所有生物体都由细胞构成。在 IGCSE Edexcel 考纲中，你需要比较动物细胞、植物细胞和细菌细胞。动物细胞包含细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞还拥有由纤维素构成的细胞壁、用于光合作用的叶绿体，以及含有细胞液的永久液泡。细菌细胞没有细胞核，其遗传物质是细胞质中的一个环状 DNA 分子，细菌可能还有质粒和荚膜。

Key points: Mitochondria are the site of aerobic respiration, providing energy. Ribosomes make proteins. Chloroplasts contain chlorophyll and absorb light for photosynthesis.
关键点：线粒体是有氧呼吸的场所，提供能量。核糖体合成蛋白质。叶绿体含有叶绿素，吸收光能用于光合作用。
Be careful with magnification calculations: magnification = image size ÷ actual size. Always write units in cm or mm consistently.
注意放大倍数的计算：放大倍数 = 像的大小 ÷ 实际大小。单位（cm 或 mm）必须保持一致。

2. Movement of Substances: Diffusion, Osmosis, Active Transport | 物质运动：扩散、渗透、主动运输

Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, down the concentration gradient, and occurs in solutions and gases. Osmosis is a special type of diffusion involving water molecules moving across a partially permeable membrane. Active transport is the movement of particles against the concentration gradient, requiring energy from respiration and carrier proteins.

扩散是粒子沿浓度梯度从高浓度区域到低浓度区域的净移动，发生在溶液和气体中。渗透是涉及水分子穿过部分通透性膜的特殊扩散类型。主动运输是粒子逆浓度梯度的移动，需要呼吸作用提供能量，并借助载体蛋白。

Water potential: water moves from higher water potential to lower water potential | 水势：水从高水势向低水势移动

In a hypotonic solution, a plant cell becomes turgid; in a hypertonic solution, it becomes plasmolysed.
在低渗溶液中，植物细胞变得坚挺（膨胀）；在高渗溶液中，细胞发生质壁分离。
Animal cells in pure water swell and burst (haemolysis) because they have no cell wall.
动物细胞在纯水中会膨胀破裂（溶血），因为没有细胞壁。

3. Enzymes and Biological Reactions | 酶与生物反应

Enzymes are biological catalysts that speed up reactions by lowering the activation energy. They are proteins with a specific active site. The lock-and-key model describes how a substrate fits exactly into the active site. Temperature and pH affect enzyme activity. As temperature increases to the optimum, the rate of reaction increases; above the optimum, the enzyme denatures and the active site changes shape permanently.

酶是生物催化剂，通过降低活化能来加快反应速度。它们是具有特定活性位点的蛋白质。锁钥模型描述了底物如何精确地契合活性位点。温度和 pH 值会影响酶活性。当温度升高至最适温度时，反应速率加快；超过最适温度后，酶变性，活性位点永久改变形状。

Optimum: the temperature/pH at which enzyme activity is maximum | 最适条件：酶活性最大的温度或 pH 值

Exam tip: Explain the shape change concept using the phrase ‘denatured active site’.
考试提示：用“活性位点变性”来解释形状变化。
Know the role of amylase (starch → maltose), protease (protein → amino acids), lipase (lipids → glycerol + fatty acids).
记住淀粉酶（淀粉→麦芽糖）、蛋白酶（蛋白质→氨基酸）、脂肪酶（脂肪→甘油+脂肪酸）的作用。

4. The Periodic Table and Atomic Structure | 元素周期表与原子结构

Atoms consist of protons, neutrons, and electrons. The proton number defines the element; the mass number is the total of protons and neutrons. In a neutral atom, the number of electrons equals the number of protons. The periodic table is arranged in groups (columns) and periods (rows). Elements in the same group have the same number of outer electrons and similar chemical properties.

原子由质子、中子和电子组成。质子数决定了元素的种类；质量数是质子数和中子数之和。在电中性原子中，电子数等于质子数。元素周期表按族（列）和周期（行）排列。同一族的元素具有相同的最外层电子数，因此化学性质相似。

Isotopes are atoms of the same element with the same proton number but different mass numbers (different number of neutrons).
同位素是质子数相同但质量数不同（中子数不同）的同种元素的原子。
Group 1 (alkali metals) become more reactive down the group; Group 7 (halogens) become less reactive down the group.
第 1 族（碱金属）从上到下反应性增强；第 7 族（卤素）从上到下反应性减弱。
For ionic bonding, metals lose electrons to form positive ions; non-metals gain electrons to form negative ions.
离子键中，金属失去电子形成正离子；非金属得到电子形成负离子。

5. Chemical Formulae, Equations, and Moles | 化学式、方程式和摩尔

Balanced chemical equations must have equal numbers of atoms of each element on both sides. The mole is a unit of amount of substance. One mole contains 6.02 × 10²³ particles. The molar mass is the mass of one mole of a substance in grams, numerically equal to the relative formula mass. You must be able to calculate moles, mass, and concentration using the triangle relationships.

配平的化学方程式必须保证反应物和生成物中各元素原子数目相等。摩尔是物质的量的单位，1 摩尔含有 6.02 × 10²³ 个粒子。摩尔质量是 1 摩尔物质的质量（单位克），数值上等于相对分子质量。你必须能够使用关系三角形计算摩尔、质量和浓度。

moles = mass (g) ÷ molar mass (g/mol) | 摩尔数 = 质量 (g) ÷ 摩尔质量 (g/mol)

concentration (mol/dm³) = moles ÷ volume (dm³) | 浓度 (mol/dm³) = 摩尔数 ÷ 体积 (dm³)

Remember the gas volume: 1 mole of any gas at room temperature and pressure (RTP) occupies 24 dm³.
记住气体体积：在任何室温常压 (RTP) 下，1 摩尔任何气体占 24 dm³。
Practice balancing equations with polyatomic ions as single units.
练习将多原子离子视为一个整体来配平方程式。

6. Acids, Bases, and Salts | 酸、碱和盐

Acids are donors of H⁺ ions in aqueous solution; bases are acceptors of H⁺ or donors of OH⁻ ions. The pH scale ranges from 0 (strongly acidic) to 14 (strongly alkaline), with 7 neutral. Acids react with metals, bases, carbonates, and alkalis to form salts. Naming salts: the first part comes from the metal or base, the second part from the acid (chloride from hydrochloric acid, sulfate from sulfuric acid, nitrate from nitric acid).

酸在水溶液中是 H⁺ 离子的给予体；碱是 H⁺ 的接受体或 OH⁻ 离子的给予体。pH 范围从 0（强酸性）到 14（强碱性），7 为中性。酸与金属、碱、碳酸盐和碱溶液反应生成盐。盐的命名：第一部分来自金属或碱，第二部分来自酸（盐酸生成氯化物，硫酸生成硫酸盐，硝酸生成硝酸盐）。

Acid + Base → Salt + Water | 酸 + 碱 → 盐 + 水

Strong acids fully ionise in water, while weak acids partially ionise.
强酸在水中完全电离，弱酸仅部分电离。
Preparing soluble salts: use titration for alkali-acid neutralisation; for insoluble salts, use precipitation.
制备可溶性盐：碱与酸中和用滴定法；不可溶性盐使用沉淀法。

7. Energy Changes in Chemistry | 化学中的能量变化

Chemical reactions involve energy changes. Exothermic reactions release heat to the surroundings, increasing the temperature (e.g., combustion, neutralisation). Endothermic reactions absorb heat from the surroundings, decreasing the temperature (e.g., thermal decomposition, photosynthesis). The energy is due to breaking bonds (requires energy) and forming bonds (releases energy).

化学反应伴随着能量变化。放热反应向周围环境释放热量，使温度升高（例如燃烧、中和）。吸热反应从周围环境吸收热量，使温度降低（例如热分解、光合作用）。能量变化源于断键（需要能量）和成键（释放能量）。

Overall energy change = energy to break bonds – energy to form bonds | 总能量变化 = 断键所需能量 – 成键释放能量

In a reaction profile, the energy level of products is lower than reactants for exothermic reactions.
在反应能量曲线图中，放热反应的生成物能量水平低于反应物。
Catalysts provide an alternative pathway with lower activation energy without being used up.
催化剂提供了较低活化能的另一反应途径，本身不会被消耗。

8. Forces and Motion | 力与运动

Speed is the distance travelled per unit time, while velocity includes direction. Acceleration is the rate of change of velocity. Newton’s second law states that force equals mass multiplied by acceleration. Weight is the force due to gravity acting on mass. You need to interpret distance-time and velocity-time graphs.

速度是单位时间内通过的距离，而速率包含方向。加速度是速度的变化率。牛顿第二定律指出力等于质量乘以加速度。重力是作用在质量上的万有引力。你需要会解读距离-时间图和速度-时间图。

F = m × a | 力 = 质量 × 加速度

weight = mass × gravitational field strength (9.8 N/kg on Earth) | 重力 = 质量 × 重力场强度（地球为 9.8 N/kg）

Gradient of a distance-time graph gives speed; gradient of a velocity-time graph gives acceleration.
距离-时间图像的斜率给出速度；速度-时间图像的斜率给出加速度。
Area under a velocity-time graph gives distance travelled.
速度-时间图像下的面积给出总路程。

9. Energy Resources and Transfers | 能源与能量转移

Energy can be stored as kinetic, gravitational potential, elastic potential, chemical, thermal, nuclear, and electromagnetic potential. Energy is conserved: it cannot be created or destroyed, only transferred. Renewable resources include solar, wind, hydroelectric, and biomass. Non-renewable resources include coal, oil, and natural gas. Efficiency is the useful output energy divided by total input energy, usually expressed as a percentage.

能量可以储存为动能、重力势能、弹性势能、化学能、热能、核能和电磁能。能量守恒定律：能量既不能被创造也不能被消灭，只能被转移。可再生能源包括太阳能、风能、水能和生物质能。不可再生资源包括煤、石油和天然气。效率等于有用输出能量除以总输入能量，通常用百分比表示。

efficiency (%) = (useful output energy ÷ total input energy) × 100 | 效率(%) = (有用输出能量 ÷ 总输入能量) × 100

Renewable resources are replenished faster than they are used, while non-renewable resources are finite.
可再生资源补充速度快于消耗速度，而不可再生资源是有限的。
Know advantages/disadvantages of different energy sources, such as reliability, environmental impact, and cost.
了解不同能源的优缺点，如可靠性、环境影响和成本。

10. Electricity and Circuits | 电与电路

Current is the flow of electric charge, measured in amperes. Potential difference (voltage) drives current. Resistance opposes current. The relationship between these is Ohm’s law. Components can be arranged in series or parallel, each with different characteristics. For series circuits, current is the same throughout, and voltages add up. For parallel circuits, voltage is the same across each branch, and currents split.

电流是电荷的流动，单位为安培。电势差（电压）驱动电流。电阻阻碍电流。它们之间的关系由欧姆定律描述。元件可以串联或并联，各自具有不同的特点。串联电路中电流处处相同，电压相加。并联电路中每条支路电压相同，电流分配。

V = I × R | 电压 = 电流 × 电阻

charge (C) = current (A) × time (s) | 电荷量 (C) = 电流 (A) × 时间 (s)

Resistance in series: R_total = R₁ + R₂ + … ; in parallel: 1/R_total = 1/R₁ + 1/R₂ + …
串联总电阻：R总 = R₁ + R₂ + …；并联：1/R总 = 1/R₁ + 1/R₂ + …
Mains electricity is alternating current (a.c.) at 230 V in the UK; cells and batteries produce direct current (d.c.).
家庭用电是交流电（a.c.），英国标准为 230 V；电池和蓄电池产生直流电（d.c.）。

11. Magnetism and Electromagnetism | 磁性与电磁学

Magnets have north and south poles. Like poles repel, unlike poles attract. A magnetic field is a region where a magnetic force is felt; field lines go from north to south. An electromagnet is a solenoid with a soft iron core, produced when a current flows. The magnetic field strength increases with more turns, a higher current, and an iron core. Electromagnetic induction is the production of a potential difference in a conductor when it cuts magnetic field lines.

磁铁具有 N 极和 S 极。同名磁极相互排斥，异名磁极相互吸引。磁场是能感受到磁力的区域，磁感线从 N 极指向 S 极。电磁铁是带有软铁芯的螺线管，当有电流通过时产生磁性。磁场强度随线圈匝数增加、电流增大以及添加铁芯而增强。电磁感应是指导体切割磁感线时产生电势差的现象。

Transformers use electromagnetic induction to change alternating voltage; step-up transformers increase voltage, step-down decrease voltage.
变压器利用电磁感应改变交流电压；升压变压器升高电压，降压变压器降低电压。
In a transformer, V_p / V_s = n_p / n_s, where n is the number of turns.
在变压器中，V_p / V_s = n_p / n_s，其中 n 是线圈匝数。

12. Radioactivity and Particle Physics | 放射性与粒子物理

Background radiation always exists. Unstable nuclei emit alpha (α), beta (β), or gamma (γ) radiation. Alpha particles are helium nuclei, positively charged, easily blocked. Beta particles are electrons, negatively charged, moderately penetrating. Gamma rays are electromagnetic waves, very penetrating. Nuclear equations must balance mass numbers and proton numbers. Half-life is the time taken for half of the radioactive nuclei to decay.

背景辐射始终存在。不稳定的原子核会发射 α、β 或 γ 射线。α 粒子是氦原子核，带正电，容易被阻挡。β 粒子是电子，带负电，穿透力中等。γ 射线是电磁波，穿透力最强。核反应方程式必须保持质量数和质子数守恒。半衰期是放射性原子核衰变一半所需的时间。

Activity/Count rate halves after each half-life | 活度/计数率在每个半衰期后减半

α particles are stopped by paper or a few cm of air; β by a few mm of aluminium; γ requires thick lead or concrete.
α 粒子被纸或几厘米空气阻挡；β 被几毫米铝阻挡；γ 需要厚铅或混凝土。
Use the equation: remaining amount = original × (0.5)^(number of half-lives)
使用公式：剩余量 = 原始量 × (0.5)^(半衰期次数)

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IGCSE Edexcel Science Revision: Mastering the Core Concepts | IGCSE Edexcel 科学复习：掌握核心概念