Combined Science 101: Core Concepts for Edexcel A-Level | 组合科学101：Edexcel A-Level 核心概念

📚 Combined Science 101: Core Concepts for Edexcel A-Level | 组合科学101：Edexcel A-Level 核心概念

Welcome to the TutorHao combined science revision guide for Edexcel A-Level students. This article brings together the highest-yield ideas from biology, chemistry and physics that appear across unit tests and practical papers. We focus on what examiners reward: precise definitions, equation use, graph skills and the ability to link concepts between disciplines.

欢迎阅读 TutorHao 为 Edexcel A-Level 学生编写的组合科学复习指南。本文汇集生物、化学和物理中单元测验与实验试卷里最高频的核心概念。我们聚焦考官看重的内容：准确的定义、公式运用、图像技能以及跨学科联系能力。

1. Exam Structure and Command Words | 考试结构与指令词

Edexcel combined science papers use command words such as state, describe, explain, calculate and evaluate. ‘State’ needs a short accurate answer; ‘describe’ needs a sequence of observations; ‘explain’ needs a scientific reason; ‘evaluate’ needs advantages, limitations and a justified conclusion.

Edexcel 组合科学试卷常使用 state、describe、explain、calculate 和 evaluate 等指令词。’State’ 需要简短准确答案；’describe’ 需要描述观察顺序；’explain’ 需要科学原因；’evaluate’ 需要优点、局限和有理有据的结论。

A common mistake is writing everything you know instead of matching the command word. Track the marks: a 2-mark ‘explain’ question usually needs a cause and a consequence, while a 4-mark ‘evaluate’ question needs at least two balanced points.

常见错误是写出所有知道的内容，却没有匹配指令词。关注分值：2 分的 ‘explain’ 题通常需要原因和结果；4 分的 ‘evaluate’ 题至少需要两个平衡的观点。

Command word	What to do
State	Give a concise fact or definition.
Describe	Write what happens, often in a logical sequence.
Explain	Give a scientific reason or mechanism.
Calculate	Show formula, substitution, answer and unit.
Evaluate	Give advantages, limitations and a justified conclusion.

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2. Atomic Structure and Isotopes | 原子结构与同位素

Atoms consist of protons, neutrons and electrons. The atomic number Z is the number of protons, while the mass number A is the total number of protons plus neutrons. For a neutral atom, electrons equal protons.

原子由质子、中子和电子构成。原子序数 Z 是质子数，质量数 A 是质子加中子的总数。中性原子中，电子数等于质子数。

A = Z + neutron number

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. They have identical chemical properties because chemical behaviour depends on electrons, but they differ in mass and some physical properties.

同位素是同一元素质子数相同、中子数不同的原子。它们化学性质相同，因为化学行为取决于电子；但质量和某些物理性质不同。

Relative atomic mass is calculated from isotopic masses and abundances. Use the weighted average: Aᵣ = Σ(isotopic mass × abundance) ÷ Σ abundance. Always check that your answer lies between the lightest and heaviest isotope.

相对原子质量由同位素质量和丰度计算得出。使用加权平均：Aᵣ = Σ(同位素质量 × 丰度) ÷ Σ 丰度。始终检查答案是否介于最轻和最重同位素之间。

Particle	Relative charge	Relative mass
Proton	+1	1
Neutron	0	1
Electron	−1	1/1836

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3. Chemical Bonding and Structure | 化学键与结构

Ionic bonding occurs when electrons are transferred from a metal to a non-metal, forming positive and negative ions. The electrostatic attraction between oppositely charged ions forms a giant ionic lattice with high melting points.

离子键是电子从金属转移到非金属，形成正负离子。相反电荷离子之间的静电引力形成巨型离子晶格，具有高熔点。

Covalent bonding involves shared pairs of electrons between non-metal atoms. Simple molecules like H₂O have strong covalent bonds inside the molecule but weak intermolecular forces between molecules, giving low boiling points.

共价键是非金属原子之间共用电子对。像 H₂O 这样的简单分子内部共价键很强，但分子之间的分子间作用力很弱，因此沸点低。

Metallic bonding is the attraction between positive metal ions and delocalised electrons. This explains electrical conductivity and malleability in metals.

金属键是正金属离子与离域电子之间的吸引。这解释了金属的导电性和延展性。

Bonding type	Particles	Typical properties
Ionic	Positive and negative ions	Hard, brittle, high melting point, conducts when molten or aqueous
Covalent simple molecular	Molecules	Low melting and boiling points, poor conductivity
Metallic	Cations and delocalised electrons	Malleable, conducts electricity and heat

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4. Moles, Equations and Quantitative Chemistry | 摩尔、方程式与定量化学

The mole is the SI unit for amount of substance. One mole contains 6.02 × 10²³ particles. The key equation is n = m / M, where n is amount in mol, m is mass in g, and M is molar mass in g mol⁻¹.

摩尔是物质的量的国际单位。1 摩尔含 6.02 × 10²³ 个粒子。关键公式 n = m / M，其中 n 是物质的量（mol），m 是质量（g），M 是摩尔质量（g mol⁻¹）。

n = m ÷ M

Concentration calculations use c = n / V with concentration in mol dm⁻³ and volume in dm³. Remember 1000 cm³ = 1 dm³. In titration questions, use n = cV to convert volumes to moles at the neutralisation point.

浓度计算用 c = n / V，浓度为 mol dm⁻³，体积为 dm³。记住 1000 cm³ = 1 dm³。在滴定题中，用 n = cV 在中和点将体积转换为摩尔。

c = n ÷ V

Balanced equations give mole ratios. If 2 mol of HCl react with 1 mol of CaCO₃, a 0.5 mol sample of CaCO₃ needs 1.0 mol HCl. Always convert given quantities to moles first, then apply the ratio.

配平方程式给出摩尔比。如果 2 mol HCl 与 1 mol CaCO₃ 反应，0.5 mol CaCO₃ 需要 1.0 mol HCl。始终先将已知量转换为摩尔，再应用比例。

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5. Forces, Motion and Newton’s Laws | 力、运动与牛顿定律

Speed is a scalar and velocity is a vector. Acceleration is the rate of change of velocity: a = (v − u) / t. Use the four suvat equations only when acceleration is constant.

速率是

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