GCSE OCR Chemistry: Last-Minute Revision Notes | GCSE OCR 化学：考前冲刺笔记

📚 GCSE OCR Chemistry: Last-Minute Revision Notes | GCSE OCR 化学：考前冲刺笔记

As your GCSE OCR Chemistry exam approaches, effective revision is crucial. These concise notes cover the core topics, focusing on key concepts, definitions, equations, and common pitfalls to help you boost your confidence and secure top marks.

随着GCSE OCR化学考试的临近，高效复习至关重要。这份精炼笔记涵盖了核心主题，聚焦关键概念、定义、方程式和常见陷阱，帮助你增强信心，夺取高分。

1. Atomic Structure and the Periodic Table | 原子结构与元素周期表

The atom consists of a nucleus containing protons (positive charge, relative mass 1) and neutrons (neutral, relative mass 1), surrounded by electrons (negative charge, relative mass 1/1840) arranged in energy levels (shells).

原子由包含质子（正电荷，相对质量1）和中子（中性，相对质量1）的原子核，以及周围按能级（电子层）排列的电子（负电荷，相对质量1/1840）构成。

Atomic number (Z) equals the number of protons, which determines the element. Mass number (A) is the total number of protons and neutrons. For atoms, the number of electrons equals the number of protons.

原子序数（Z）等于质子数，决定了元素的种类。质量数（A）是质子数与中子数之和。在原子中，电子数等于质子数。

Electrons occupy shells: the first shell holds up to 2 electrons, the second and third shells up to 8 electrons each. Electronic configuration is written as e.g. sodium: 2,8,1.

电子排布：第一层最多容纳2个电子，第二、三层最多容纳8个电子。电子排布式如钠为2,8,1。

The Periodic Table arranges elements in order of atomic number. Groups (vertical columns) have the same number of outer-shell electrons, leading to similar chemical properties. Periods (horizontal rows) show the number of electron shells.

周期表按原子序数递增排列。族（纵列）具有相同的外层电子数，因此化学性质相似。周期（横行）表明电子层数。

Group 1 (alkali metals) are very reactive; reactivity increases down the group. Group 7 (halogens) are reactive non-metals; reactivity decreases down the group. Group 0 (noble gases) are unreactive due to full outer shells.

第1族（碱金属）非常活泼，活泼性自上而下增强。第7族（卤素）为活泼非金属，活泼性自上而下减弱。第0族（稀有气体）因外层电子已满而化学性质不活泼。

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

Ionic bonding occurs between metals and non-metals, involving transfer of electrons to form oppositely charged ions held by strong electrostatic forces. Ionic compounds form giant ionic lattices with high melting/boiling points; they conduct electricity when molten or dissolved because ions are free to move.

离子键存在于金属与非金属之间，通过电子转移形成带相反电荷的离子，靠强静电引力结合。离子化合物形成巨型离子晶格，熔沸点高；在熔融或溶解时能导电，因离子可自由移动。

Covalent bonding occurs between non-metals, sharing electron pairs to achieve a full outer shell. Substances can be simple molecular (e.g. H₂O, CO₂) with low melting points and no electrical conductivity, or giant covalent structures (e.g. diamond, graphite, SiO₂) with very high melting points. Graphite conducts electricity due to delocalised electrons between layers.

共价键存在于非金属之间，通过共用电子对达到满壳层。物质可以是简单分子（如水、二氧化碳），熔沸点低且不导电；也可以是巨型共价结构（如金刚石、石墨、二氧化硅），熔沸点极高。石墨因层间有离域电子而导电。

Metallic bonding involves a lattice of positive ions surrounded by a ‘sea’ of delocalised electrons. Metals are good conductors of heat and electricity, and are malleable and ductile.

金属键由正离子晶格和“海洋”般的离域电子构成。金属是热和电的良导体，具有延展性。

Alloys are mixtures of a metal with other elements; the different-sized atoms disrupt the regular lattice structure, making them harder and less malleable than pure metals.

合金是金属与其他元素的混合物；大小不同的原子打乱了规则的晶格结构，使合金比纯金属更硬、延展性更差。

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3. Quantitative Chemistry | 定量化学

Relative atomic mass (Aᵣ) is the mean mass of an atom relative to 1/12th the mass of carbon-12. Relative formula mass (Mᵣ) is the sum of the Aᵣ of all atoms in a formula unit.

相对原子质量（Aᵣ）是原子的平均质量相对于碳-12质量的1/12。相对式量（Mᵣ）是一个式单元中所有原子的Aᵣ之和。

A mole is the amount of substance containing 6.02 × 10²³ particles (Avogadro constant). Mass of one mole = relative formula mass in grams. Number of moles = mass (g) ÷ Mᵣ.

摩尔是含有6.02×10²³个粒子的物质的量（阿伏伽德罗常数）。一摩尔的质量等于以克为单位的相对式量。摩尔数 = 质量(g) ÷ Mᵣ。

Concentration of a solution (mol/dm³) = number of moles ÷ volume (dm³). For titrations, use the ratio of moles from the balanced equation.

溶液的浓度（mol/dm³）= 摩尔数 ÷ 体积(dm³)。对于滴定，利用配平方程式中的摩尔比进行计算。

Reacting masses: from a balanced equation, use mole ratios to calculate the mass of a product or reactant. Percentage yield = (actual yield ÷ theoretical yield) × 100%. Atom economy = (Mᵣ of desired product ÷ sum of Mᵣ of all reactants) × 100%.

反应质量：依据配平方程式，利用摩尔比计算产物或反应物的质量。产率百分比 = (实际产量 ÷ 理论产量) × 100%。原子经济性 = (目标产物Mᵣ ÷ 所有反应物的Mᵣ总和) × 100%。

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4. Chemical Changes and Electrolysis | 化学变化与电解

Reactivity series: metals are arranged in order of reactivity. A more reactive metal displaces a less reactive metal from its compound. Carbon can be used to extract metals below it in the series from their oxides by reduction.

金属活泼性顺序：金属按反应活性排列。活泼金属能从化合物中置换出较不活泼金属。碳可用于从其氧化物中还原提取比碳不活泼的金属。

Oxidation is loss of electrons; Reduction is gain of electrons (OIL RIG). In terms of oxygen, oxidation is gain of oxygen, reduction is loss of oxygen.

氧化是失电子；还原是得电子（OIL RIG）。从氧的角度，氧化是得氧，还原是失氧。

Electrolysis is the decomposition of an ionic compound using direct current. The electrolyte is the molten or dissolved ionic substance. Positive ions (cations) move to the cathode (negative electrode) and gain electrons (reduction). Negative ions

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