IGCSE Science Revision: Key Concepts in Biology, Chemistry and Physics | IGCSE科学复习：生物、化学和物理关键概念

📚 IGCSE Science Revision: Key Concepts in Biology, Chemistry and Physics | IGCSE科学复习：生物、化学和物理关键概念

This revision guide summarises the core ideas you need for Edexcel IGCSE Science. It covers essential biological processes, chemical principles and physical laws in a compact, exam-focused format.

本复习指南总结了 Edexcel IGCSE 科学考试所需的核心概念。它用紧凑、面向考试的形式涵盖了重要的生物过程、化学原理和物理定律。

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

All living organisms are made of cells. Animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells also have a cell wall, chloroplasts and a permanent vacuole.

所有生物体都由细胞构成。动物细胞含有细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞还具有细胞壁、叶绿体和永久液泡。

Nucleus – controls cell activities and contains DNA.

细胞核 – 控制细胞活动并含有 DNA。
Mitochondria – site of aerobic respiration.

线粒体 – 有氧呼吸的场所。
Chloroplasts – site of photosynthesis, contain chlorophyll.

叶绿体 – 光合作用的场所，含有叶绿素。
Cell wall – made of cellulose, provides support.

细胞壁 – 由纤维素构成，提供支撑。

Magnification = Image size ÷ Actual size

放大倍数 = 图像大小 ÷ 实际大小

2. Diffusion, Osmosis and Active Transport | 扩散、渗透与主动运输

Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration. Osmosis is the net movement of water molecules across a partially permeable membrane from a dilute solution to a more concentrated one.

扩散是粒子从高浓度区域到低浓度区域的净移动。渗透是水分子通过部分通透性膜从稀溶液到较浓溶液的净移动。

Active transport moves substances against the concentration gradient, using energy from respiration. It allows root hairs to absorb mineral ions from very dilute soil solutions.

主动运输逆浓度梯度移动物质，利用呼吸作用产生的能量。它使根毛能够从非常稀的土壤溶液中吸收矿质离子。

Diffusion – no energy needed, passive.

扩散 – 不需要能量，是被动过程。
Osmosis – water only, through a membrane.

渗透 – 只涉及水，通过膜进行。
Active transport – needs energy, against gradient.

主动运输 – 需要能量，逆梯度进行。

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

Enzymes are biological catalysts that speed up reactions without being used up. They are proteins with a specific active site that fits a particular substrate.

酶是生物催化剂，能加快反应速度而自身不被消耗。它们是具有特定活性位点的蛋白质，该活性位点与特定底物相匹配。

Enzyme activity is affected by temperature and pH. High temperatures denature the enzyme, changing the shape of its active site. Each enzyme has an optimum pH.

酶活性受温度和 pH 值影响。高温使酶变性，改变其活性位点的形状。每种酶都有一个最适 pH 值。

Factor	Effect on enzyme
Temperature increase	Rate increases up to optimum, then falls rapidly.
pH change	Extreme pH denatures the enzyme.

温度升高 – 在最适温度前速率上升，之后迅速下降。pH 变化 – 极端 pH 会使酶变性。

4. Photosynthesis and Respiration | 光合作用与呼吸作用

Photosynthesis converts carbon dioxide and water into glucose and oxygen using light energy. The equation is:

光合作用利用光能将二氧化碳和水转化为葡萄糖和氧气。方程式为：

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

6 二氧化碳 + 6 水 → 葡萄糖 + 6 氧气

Aerobic respiration releases energy from glucose using oxygen. Anaerobic respiration in humans produces lactic acid and less energy.

有氧呼吸利用氧气从葡萄糖中释放能量。人体无氧呼吸产生乳酸，释放的能量较少。

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

葡萄糖 + 6 氧气 → 6 二氧化碳 + 6 水 + 能量

Photosynthesis is affected by light intensity, carbon dioxide concentration and temperature. Limiting factors are essential in exam questions.

光合作用受光照强度、二氧化碳浓度和温度影响。限制因子在考试题目中很重要。

5. Atoms, Elements and Compounds | 原子、元素与化合物

An atom is the smallest unit of an element. It has a nucleus containing protons and neutrons, with electrons orbiting in shells. Atomic number is the number of protons; mass number is protons plus neutrons.

原子是元素的最小单位。它有一个包含质子和中子的原子核，电子在壳层中绕核运动。原子序数是质子数；质量数是质子数加中子数。

Isotopes are atoms of the same element with different numbers of neutrons. For example, carbon-12 and carbon-14 are isotopes of carbon.

同位素是同一元素中具有不同中子数的原子。例如，碳-12 和碳-14 是碳的同位素。

Proton – +1 charge, mass 1.

质子 – +1 电荷，质量 1。
Neutron – 0 charge, mass 1.

中子 – 0 电荷，质量 1。
Electron – -1 charge, mass ~1/1836.

电子 – -1 电荷，质量约为 1/1836。

Number of electrons = Number of protons (in a neutral atom)

电子数 = 质子数（中性原子中）

6. Ionic and Covalent Bonding | 离子键与共价键

Ionic bonding occurs between metals and non-metals. Electrons are transferred from the metal to the non-metal, forming positive and negative ions held together by electrostatic forces.

离子键发生在金属和非金属之间。电子从金属转移到非金属，形成由静电作用力结合的正离子和负离子。

Covalent bonding occurs between non-metals. Atoms share pairs of electrons to achieve a full outer shell. Simple molecules like H₂O and CO₂ are covalently bonded.

共价键发生在非金属之间。原子共享电子对以获得满外层电子。像 H₂O 和 CO₂ 这样的简单分子通过共价键结合。

Ionic compounds have high melting points and conduct electricity when molten or dissolved. Covalent molecular substances have low melting points and do not conduct electricity.

离子化合物熔点高，在熔融或溶解时能导电。共价分子物质熔点低，不导电。

7. Chemical Calculations and Moles | 化学计算与摩尔

The mole is a unit for counting particles. One mole contains 6.02 × 10²³ particles, known as Avogadro’s constant.

摩尔是用于计数粒子的单位。一摩尔含有 6.02 × 10²³ 个粒子，称为阿伏伽德罗常数。

Moles = Mass (g) ÷ Molar mass (g/mol)

摩尔数 = 质量（克） ÷ 摩尔质量（克/摩尔）

In a balanced equation, the coefficients give the mole ratio. For example, 2H₂ + O₂ → 2H₂O means 2 moles of hydrogen react with 1 mole of oxygen.

在配平的方程式中，系数给出摩尔比。例如，2H₂ + O₂ → 2H₂O 表示 2 摩尔氢气与 1 摩尔氧气反应。

Concentration is calculated as moles per cubic decimetre. Always convert cm³ to dm³ by dividing by 1000.

浓度计算为每立方分米的摩尔数。将 cm³ 转换为 dm³ 时总是除以 1000。

Concentration (mol/dm³) = Moles ÷ Volume (dm³)

浓度（摩尔/立方分米）= 摩尔数 ÷ 体积（立方分米）

8. Acids, Bases and Salts | 酸、碱与盐

Acids release H⁺ ions in water; bases release OH⁻ ions. Neutralisation is the reaction between an acid and a base to produce a salt and water.

酸在水中释放 H⁺ 离子；碱释放 OH⁻ 离子。中和反应是酸和碱之间的反应，生成盐和水。

H⁺(aq) + OH⁻(aq) → H₂O(l)

H⁺（水溶液） + OH⁻（水溶液） → H₂O（液体）

The pH scale measures acidity. pH 0-6 is acidic, pH 7 is neutral, pH 8-14 is alkaline. Universal indicator changes colour with pH.

pH 标度用于测量酸碱性。pH 0-6 为酸性，pH 7 为中性，pH 8-14 为碱性。万能指示剂随 pH 变化而改变颜色。

Salt preparation uses methods such as titration and excess solid. Common salts include sodium chloride and copper sulfate.

盐的制备使用滴定和过量固体等方法。常见盐包括氯化钠和硫酸铜。

9. Motion, Forces and Energy | 运动、力与能量

Speed is distance divided by time. Velocity includes direction. Acceleration is the change in velocity per unit time.

速率等于距离除以时间。速度包括方向。加速度是单位时间内速度的变化量。

Speed = Distance ÷ Time

速率 = 距离 ÷ 时间

Newton’s second law relates force, mass and acceleration: F = ma. Weight is the force due to gravity, calculated as mass × gravitational field strength (g = 9.8 N/kg).

牛顿第二定律将力、质量和加速度联系起来：F = ma。重力是重力引起的力，计算公式为质量 × 重力场强度（g = 9.8 N/kg）。

Energy stores include kinetic, gravitational potential, elastic, chemical, thermal and electrical. Work done is force × distance.

能量储存形式包括动能、重力势能、弹性势能、化学能、内能和电能。做功等于力 × 距离。

Kinetic Energy = ½mv²

动能 = ½mv²

Gravitational Potential Energy = mgh

重力势能 = mgh

10. Electricity and Magnetism | 电与磁

Current is the flow of charge. Potential difference (voltage) pushes the charge around a circuit. Resistance opposes the flow of current.

电流是电荷的流动。电势差（电压）推动电荷在电路中运动。电阻阻碍电流的流动。

V = I × R

电压 = 电流 × 电阻

Series circuits have one loop; current is the same everywhere, while voltage is shared. Parallel circuits have branches; voltage is the same across each branch, while current is shared.

串联电路只有一条回路；各处电流相同，而电压被分配。并联电路有分支；每个分支两端的电压相同，而电流被分配。

Magnets have north and south poles. Like poles repel, unlike poles attract. When current flows through a wire, a magnetic field is created around it.

磁铁有北极和南极。同名磁极相斥，异名磁极相吸。当电流通过导线时，导线周围会产生磁场。

11. Waves and the Electromagnetic Spectrum | 波与电磁波谱

Waves transfer energy without transferring matter. Transverse waves vibrate perpendicular to the direction of travel; longitudinal waves vibrate parallel.

波传递能量而不传递物质。横波的振动方向垂直于传播方向；纵波的振动方向平行于传播方向。

Wave speed = Frequency × Wavelength

波速 = 频率 × 波长

The electromagnetic spectrum, in order of increasing frequency, is: radio, microwave, infrared, visible light, ultraviolet, X-ray, gamma ray. All travel at the speed of light in a vacuum.

电磁波谱按频率从低到高排列为：无线电波、微波、红外线、可见光、紫外线、X 射线、伽马射线。所有电磁波在真空中都以光速传播。

In IGCSE, you should relate each wave type to a use and a danger. For example, X-rays are used for medical imaging but can damage cells.

在 IGCSE 考试中，你应该将每种波与一种用途和一种危害联系起来。例如，X 射线用于医学成像，但可能损伤细胞。

12. Radioactivity and the Environment | 放射性与环境

Radioactive decay is a random process in which unstable nuclei lose energy by emitting radiation. The three main types are alpha, beta and gamma.

放射性衰变是不稳定原子核通过发射辐射而损失能量的随机过程。三种主要类型是 α、β 和 γ 辐射。

Alpha (α) – helium nucleus, low penetration, high ionising power.

阿尔法（α）– 氦原子核，穿透力低，电离能力强。
Beta (β) – fast-moving electron, moderate penetration.

贝塔（β）– 快速运动的电子，穿透力中等。
Gamma (γ) – electromagnetic wave, high penetration, low ionising power.

伽马（γ）– 电磁波，穿透力高，电离能力低。

Activity = Number of decays per second

活度 = 每秒衰变次数

Half-life is the time taken for half the radioactive nuclei in a sample to decay. Radioactivity is used in medicine, dating fossils and generating electricity, but also poses risks such as cancer.

半衰期是样品中一半放射性原子核发生衰变所需的时间。放射在医学、化石测年和发电中有应用，但也带来癌症等风险。

Published by TutorHao | Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

IGCSE Science Revision: Key Concepts in Biology, Chemistry and Physics | IGCSE科学复习：生物、化学和物理关键概念