Edexcel A-Level Combined Science (078) Revision Guide | Edexcel A-Level 综合科学 (078) 复习指南

📚 Edexcel A-Level Combined Science (078) Revision Guide | Edexcel A-Level 综合科学 (078) 复习指南

Welcome to your comprehensive revision guide for Edexcel A-Level Combined Science (078). This subject integrates biology, chemistry, and physics into a single coherent framework, testing your ability to apply principles across traditional subject boundaries. The guide below follows the Edexcel specification, focusing on high-yield topics, common pitfalls, and exam-style reasoning.

欢迎阅读 Edexcel A-Level 综合科学 (078) 的全面复习指南。本学科将生物、化学和物理整合为单一连贯体系，考查你在传统学科边界之间应用原理的能力。以下指南遵循 Edexcel 考纲，聚焦高频考点、常见误区和考试型推理。

1. Working Scientifically | 科学探究方法

In Edexcel Combined Science, you must demonstrate competence in independent variables, dependent variables, and control variables. You should be able to design experiments, identify errors, and suggest improvements. Quantitative skills include calculating percentages, ratios, uncertainties, and using standard form.

在 Edexcel 综合科学中，你必须展示对自变量、因变量和控制变量的掌握能力。你应该能够设计实验、识别误差并提出改进方案。量化技能包括计算百分比、比值、不确定度以及使用科学计数法。

Always state a clear hypothesis before describing a method.

在描述方法之前，务必先提出清晰的假说。
When calculating percentage uncertainty: uncertainty ÷ measurement × 100%.

计算百分比不确定度时：不确定度 ÷ 测量值 × 100%。
For control variables, explain why each one must be kept constant.

对于控制变量，要解释为什么每个变量都必须保持恒定。

Example calculation: A mass of 25.0 g is measured with an uncertainty of ±0.1 g. Percentage uncertainty = (0.1 ÷ 25.0) × 100% = 0.4%.

示例计算：质量为 25.0 g，不确定度为 ±0.1 g。百分比不确定度 = (0.1 ÷ 25.0) × 100% = 0.4%。

2. Cell Structure and Transport | 细胞结构与物质运输

Eukaryotic cells contain membrane-bound organelles, including mitochondria, chloroplasts (in plants), and the nucleus. Prokaryotic cells lack a nucleus and membrane-bound organelles. You should compare magnification, resolution, and the structures visible under light and electron microscopes.

真核细胞含有膜结合细胞器，包括线粒体、叶绿体（植物中）和细胞核。原核细胞没有细胞核和膜结合细胞器。你需要比较放大倍数、分辨率以及光学显微镜和电子显微镜下可见的结构。

Magnification = Image size ÷ Actual size

放大倍数 = 像的大小 ÷ 实际大小

Transport across membranes can be passive (simple diffusion, facilitated diffusion, osmosis) or active (active transport). Remember that simple diffusion does not require proteins or ATP; facilitated diffusion uses channel or carrier proteins but no ATP; active transport uses carrier proteins and ATP.

跨膜运输可以是被动运输（简单扩散、易化扩散、渗透）或主动运输。记住：简单扩散不需要蛋白质或 ATP；易化扩散使用通道蛋白或载体蛋白但不消耗 ATP；主动运输使用载体蛋白并消耗 ATP。

Osmosis is the net movement of water from a higher water potential to a lower water potential across a partially permeable membrane.

渗透是水从较高水势经部分通透膜向较低水势的净移动。
In animal cells, a hypotonic solution causes bursting (lysis); in plant cells, turgor pressure is maintained by the cell wall.

在动物细胞中，低渗溶液会导致破裂（裂解）；在植物细胞中，膨胀压由细胞壁维持。

3. Biological Molecules | 生物分子

Carbohydrates, proteins, lipids, and nucleic acids are the four major classes of biological molecules. For carbohydrates, glucose (C₆H₁₂O₆) is the key monomer. Starch and glycogen are storage polysaccharides, while cellulose is structural.

碳水化合物、蛋白质、脂质和核酸是四大类生物分子。对于碳水化合物，葡萄糖（C₆H₁₂O₆）是关键单体。淀粉和糖原是储存多糖，而纤维素是结构多糖。

Proteins are polymers of amino acids joined by peptide bonds. The primary structure is the amino acid sequence; secondary structure includes α-helices and β-pleated sheets; tertiary structure is the overall 3D shape; quaternary structure involves multiple polypeptide chains.

蛋白质是由氨基酸通过肽键连接而成的聚合物。一级结构是氨基酸序列；二级结构包括α-螺旋和β-折叠片；三级结构是整体三维形状；四级结构涉及多条多肽链。

Enzymes lower activation energy and are specific to their substrate.

酶降低活化能并对底物具有专一性。

Remember the Benedict’s test for reducing sugars, iodine for starch, Biuret for proteins, and emulsion test for lipids.

记住：本尼迪特试剂检验还原糖、碘检验淀粉、双缩脲试剂检验蛋白质、乳化试验检验脂质。

4. Atomic Structure and the Periodic Table | 原子结构与周期表

An atom consists of protons, neutrons, and electrons. The atomic number (Z) equals the number of protons; the mass number (A) equals protons + neutrons. Isotopes are atoms of the same element with different numbers of neutrons.

原子由质子、中子和电子组成。原子序数（Z）等于质子数；质量数（A）等于质子 + 中子。同位素是质子数相同但中子数不同的同种元素的原子。

Relative atomic mass = Σ(isotopic mass × abundance) ÷ total abundance

相对原子质量 = Σ(同位素质量 × 丰度) ÷ 总丰度

In the periodic table, elements are arranged in order of increasing atomic number. Group number indicates the number of outer-shell electrons (for groups 1-2 and 13-18). Period number indicates the number of electron shells.

在周期表中，元素按原子序数递增排列。族号表示外层电子数（对第1-2族和第13-18族）。周期号表示电子壳层数。

Metals lose electrons to form positive ions; non-metals gain electrons to form negative ions.

金属失去电子形成正离子；非金属得到电子形成负离子。
Ionic bonding occurs between a metal and a non-metal; covalent bonding occurs between non-metals.

离子键发生在金属与非金属之间；共价键发生在非金属之间。

5. Bonding, Structure and Properties | 化学键、结构与性质

There are four main types of structure you need to compare: giant ionic, giant covalent (diamond, graphite, silicon dioxide), simple molecular (e.g., H₂O, CO₂), and metallic. Each structure explains physical properties such as melting point, boiling point, and electrical conductivity.

你需要比较四种主要结构类型：巨型离子、巨型共价（金刚石、石墨、二氧化硅）、简单分子（如 H₂O、CO₂）和金属。每种结构都能解释熔点、沸点和导电性等物理性质。

Giant ionic structures have high melting points due to strong electrostatic forces between ions. Simple molecular substances have low melting points because only weak intermolecular forces need to be overcome.

巨型离子结构由于离子之间存在强静电作用力而具有高熔点。简单分子物质熔点低，因为只需克服微弱的分子间作用力。

Structure	Melting point	Conductivity
Giant ionic	High	When molten or aqueous
Giant covalent (diamond)	Very high	None (except graphite)
Simple molecular	Low	None
Metallic	Variable	Good (solid and liquid)

Structure | 熔点 | 导电性

6. Quantitative Chemistry and Equations | 定量化学与方程式

You must be able to balance chemical equations and calculate moles using the formula: moles = mass ÷ molar mass. The mole concept is central to stoichiometry. For gases, volume (dm³) = moles × 24 dm³ mol⁻¹ at room temperature and pressure.

你必须能够配平化学方程式，并使用公式计算物质的量：物质的量 = 质量 ÷ 摩尔质量。物质的量概念是化学计量学的核心。对于气体，在室温常压下体积（dm³）= 物质的量 × 24 dm³ mol⁻¹。

n = m / M | n = V / 24 (at RTP)

n = m / M | n = V / 24（室温常压下）

For solution chemistry: concentration (mol dm⁻³) = moles ÷ volume (dm³). Always convert cm³ to dm³ by dividing by 1000.

对于溶液化学：浓度（mol dm⁻³）= 物质的量 ÷ 体积（dm³）。始终将 cm³ 除以 1000 换算为 dm³。

When performing titration calculations, use the equation C₁V₁ = C₂V₂ only when the reacting ratio is 1:1. Otherwise, use moles and stoichiometric ratios.

进行滴定计算时，仅在反应比率为 1:1 时才使用 C₁V₁ = C₂V₂ 公式。否则，应使用物质的量和化学计量比。

7. Energy Changes and Reaction Rates | 能量变化与反应速率

Exothermic reactions release heat to the surroundings (ΔH negative); endothermic reactions absorb heat (ΔH positive). Activation energy is the minimum energy needed for a successful collision.

放热反应向周围释放热量（ΔH 为负）；吸热反应吸收热量（ΔH 为正）。活化能是发生有效碰撞所需的最小能量。

Reaction rates are affected by temperature, concentration, pressure (for gases), surface area, and catalysts. A catalyst provides an alternative pathway with lower activation energy, increasing the rate without being consumed.

反应速率受温度、浓度、压力（对气体）、表面积和催化剂的影响。催化剂提供了一条活化能较低的反应路径，从而提高速率且自身不被消耗。

Rate ∝ 1 / time (if the reaction produces a measurable change)

速率 ∝ 1 / 时间（如果反应产生可测变化）

In collision theory, increasing temperature increases the proportion of particles with energy greater than the activation energy, not just the average speed.

在碰撞理论中，升高温度会增加能量超过活化能的粒子比例，而不仅仅是提高平均速度。

8. Forces, Motion and Energy | 力、运动与能量

Kinematics equations apply to uniform acceleration. The key equations are v = u + at, s = ut + ½at², and v² = u² + 2as. Remember to define a positive direction and use consistent units (m, s, m/s, m/s²).

运动学方程适用于匀加速运动。关键方程：v = u + at、s = ut + ½at²、v² = u² + 2as。记住定义正方向并使用一致单位（m、s、m/s、m/s²）。

Newton’s laws: (1) an object stays at rest or in uniform motion unless acted on by a resultant force; (2) F = ma; (3) every action has an equal and opposite reaction.

牛顿定律：（1）物体在不受合外力时保持静止或匀速直线运动；（2）F = ma；（3）每个作用力都有大小相等方向相反的反作用力。

Energy conservation: gravitational potential energy (GPE) = mgh; kinetic energy (KE) = ½mv². In a closed system, energy cannot be created or destroyed.

能量守恒：重力势能（GPE）= mgh；动能（KE）= ½mv²。在封闭系统中，能量不能被创造或消灭。

Work done = Force × Distance | Power = Work done ÷ Time

功 = 力 × 距离 | 功率 = 功 ÷ 时间

Momentum = mass × velocity. It is conserved in collisions with no external forces.

动量 = 质量 × 速度。在无外力碰撞中动量守恒。
Efficiency = (useful output ÷ total input) × 100%.

效率 =（有用输出 ÷ 总输入）× 100%。

9. Electricity and Circuits | 电学与电路

Current (I) is the rate of flow of charge, measured in amperes. Voltage (V) is the energy per unit charge transferred between points. Resistance (R) opposes current. Ohm’s law states V = IR for a constant temperature.

电流（I）是电荷流动的速率，单位为安培。电压（V）是单位电荷在两点之间转移的能量。电阻（R）阻碍电流。欧姆定律指出在恒定温度下 V = IR。

Series circuits: total resistance = sum of individual resistances; current is the same everywhere, but voltage is shared. Parallel circuits: voltage is the same across each branch; currents add up.

串联电路：总电阻 = 各电阻之和；电流处处相同，电压分配。并联电路：每条支路两端电压相同；电流相加。

Electrical power = V × I = I²R = V²/R

电功率 = V × I = I²R = V²/R

Energy transferred = power × time = VIt. Be careful with units: time in seconds, energy in joules.

传递能量 = 功率 × 时间 = VIt。注意单位：时间用秒，能量用焦耳。

For IV characteristics, a resistor is ohmic (straight line through origin); a filament lamp shows increasing resistance; a diode conducts in only one direction.

对于 I-V 特性：电阻是欧姆性的（过原点的直线）；白炽灯显示电阻增大；二极管仅单向导通。

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

Waves transfer energy without transferring matter. Transverse waves have oscillations perpendicular to the direction of energy transfer (light, water waves). Longitudinal waves have oscillations parallel (sound waves).

波传递能量但不传递物质。横波的振动方向垂直于能量传播方向（光、水波）。纵波的振动方向平行（声波）。

Wave speed = frequency × wavelength (v = fλ)

波速 = 频率 × 波长（v = fλ）

The electromagnetic spectrum in order of increasing frequency: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Higher frequency means shorter wavelength and higher energy.

电磁波谱按频率递增顺序：无线电波、微波、红外线、可见光、紫外线、X射线、γ射线。频率越高，波长越短，能量越高。

All electromagnetic waves travel at the same speed in a vacuum: 3.0 × 10⁸ m/s.

所有电磁波在真空中的速度相同：3.0 × 10⁸ m/s。
Reflection obeys the law: angle of incidence = angle of reflection.

反射遵循定律：入射角 = 反射角。
Refraction occurs because the wave speed changes when moving between media.

折射发生是因为波在不同介质中传播速度改变。

11. The Human Body and Homeostasis | 人体与体内稳态

Homeostasis maintains a steady internal environment. Negative feedback mechanisms counteract changes. Key examples include blood glucose control (insulin and glucagon), body temperature control, and water balance (ADH).

体内稳态维持内环境的稳定。负反馈机制抵消变化。关键示例包括血糖控制（胰岛素和胰高血糖素）、体温控制和水盐平衡（ADH）。

Insulin is secreted by β-cells of the pancreas when glucose is high. It promotes glucose uptake by cells and glycogenesis in the liver. Glucagon is secreted by α-cells when glucose is low, promoting glycogenolysis.

当血糖升高时，胰腺β细胞分泌胰岛素。它促进细胞摄取葡萄糖并促进肝脏中的糖原合成。当血糖降低时，α细胞分泌胰高血糖素，促进糖原分解。

Negative feedback: stimulus → receptor → coordinator → effector → response → reduces stimulus

负反馈：刺激 → 感受器 → 协调器 → 效应器 → 反应 → 减小刺激

For temperature control: the hypothalamus acts as the thermostat. Sweating, vasodilation, and increased respiration rate cool the body; shivering, vasoconstriction, and increased metabolic rate warm it.

对于体温调节：下丘脑作为恒温器。出汗、血管舒张和呼吸速率加快可降低体温；寒战、血管收缩和代谢速率加快可升高体温。

12. Genetics, Evolution and Data Analysis | 遗传、进化与数据分析

DNA is a double helix made of nucleotides. Each nucleotide has a phosphate group, deoxyribose sugar, and a nitrogenous base (A, T, G, C). Complementary base pairing: A-T, G-C.

DNA 是双螺旋结构，由核苷酸构成。每个核苷酸包含一个磷酸基团、脱氧核糖和一个含氮碱基（A、T、G、C）。互补碱基配对：A-T、G-C。

Genes are sequences of DNA that code for proteins. Alleles are different versions of a gene. Dominant alleles mask recessive alleles. Monohybrid inheritance can be analysed using genetic cross diagrams and Punnett squares.

基因是编码蛋白质的 DNA 序列。等位基因是一个基因的不同版本。显性等位基因掩盖隐性等位基因。单因子杂交可用遗传图解和庞尼特方格分析。

Natural selection: individuals with advantageous phenotypes are more likely to survive and reproduce, passing on their alleles. This leads to evolution over many generations.

自然选择：具有有利表型的个体更可能生存并繁殖，将其等位基因遗传下去。经过许多世代，这导致了进化。

In data analysis, you should calculate mean, median, mode, and standard deviation when interpreting biological data. Always use error bars to evaluate reliability and statistical significance.

在数据分析中，解释生物数据时应计算平均数、中位数、众数和标准差。始终使用误差条来评估可靠性和统计显著性。

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Edexcel A-Level Combined Science (078) Revision Guide | Edexcel A-Level 综合科学 (078) 复习指南