Displacement Reactions: KS3 CIE Mark Scheme Guide | 置换反应：KS3 CIE 评分标准指南

📚 Displacement Reactions: KS3 CIE Mark Scheme Guide | 置换反应：KS3 CIE 评分标准指南

This revision guide explains exactly what examiners look for in KS3 CIE displacement reaction questions. It breaks down key definitions, common equations, observation mark points, and the wording that appears in mark schemes so you can answer with confidence.

本复习指南解释考官在 KS3 CIE 置换反应题目中究竟考查什么。它拆解关键定义、常见方程式、现象给分点和评分标准中的措辞，帮助你自信作答。

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1. What Displacement Reactions Are | 什么是置换反应

In a displacement reaction, a more reactive element takes the place of a less reactive element inside a compound. The less reactive element is released as a pure substance. Most KS3 CIE questions focus on metals displacing other metals from salt solutions.

在置换反应中，较活泼的元素取代化合物中较不活泼的元素。较不活泼的元素以单质形式释放出来。KS3 CIE 的题目大多关注金属从盐溶液中置换出另一种金属。

For example, when zinc is added to copper(II) sulfate solution, zinc displaces copper because zinc is more reactive than copper. The blue copper(II) sulfate solution fades, and reddish-brown copper metal forms.

例如，将锌加入硫酸铜(II)溶液中，锌会置换出铜，因为锌比铜活泼。蓝色的硫酸铜(II)溶液颜色变浅，并生成红棕色铜金属。

Mark schemes often award one mark for naming the more reactive metal and one mark for saying the less reactive metal is displaced. A third mark may be given for a correct word equation.

评分标准通常给 1 分用于指出较活泼金属，另 1 分用于说明较不活泼金属被置换出来。第 3 分可能用于正确的文字表达式。

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2. The Reactivity Series You Must Recall | 必须记住的金属活动性顺序

The reactivity series lists metals in order of how vigorously they react. A metal higher in the series can displace a metal lower in the series from a solution of its salt.

金属活动性顺序按金属反应的剧烈程度排列。顺序中位置较高的金属可以从位置较低金属的盐溶液中将其置换出来。

For KS3 CIE, you should recall this simplified order from most reactive to least reactive:

KS3 CIE 要求记住以下从最活泼到最不活泼的简化顺序：

K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag > Au

Metal	Symbol	Reactivity note | 活泼性说明
Potassium | 钾	K	Most reactive; stored under oil | 最活泼；保存在油中
Sodium | 钠	Na	Very reactive; reacts quickly with water | 非常活泼；与水迅速反应
Calcium | 钙	Ca	Reactive; forms calcium salts | 活泼；形成钙盐
Magnesium | 镁	Mg	Reactive; burns with a bright white flame | 活泼；燃烧时发出耀眼白光
Aluminium | 铝	Al	Reactive; protected by an oxide layer | 活泼；被氧化膜保护
Zinc | 锌	Zn	Fairly reactive; displaces copper and iron | 较活泼；可置换铜和铁
Iron | 铁	Fe	Displaces copper from copper salts | 可从铜盐中置换铜
Lead | 铅	Pb	Less reactive than zinc and iron | 不如锌和铁活泼
Copper | 铜	Cu	Low reactivity; often displaced | 活泼性低；常被置换出来
Silver | 银	Ag	Very low reactivity | 活泼性很低
Gold | 金	Au	Least reactive metal | 最不活泼的金属

Examiners do not expect you to memorise every numerical value. They expect you to compare two metals and decide which one is higher in the series.

考官并不要求记住每个数值。他们要求你比较两种金属，判断哪一种在顺序中位置更高。

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3. The Standard Word Equation Pattern | 标准文字表达式模式

Displacement reactions follow a predictable word equation pattern. If you can recognise the pattern, you can write word equations without memorising each reaction separately.

置换反应遵循可预测的文字表达式模式。如果能识别这一模式，就无需单独背诵每个反应，也能写出文字表达式。

more reactive metal + metal salt solution → less reactive metal + more reactive metal salt solution

较活泼金属 + 金属盐溶液 → 较不活泼金属 + 较活泼金属盐溶液

For example, zinc added to copper(II) sulfate solution gives:

例如，锌加入硫酸铜(II)溶液会得到：

zinc + copper(II) sulfate → copper + zinc sulfate

锌 + 硫酸铜(II) → 铜 + 硫酸锌

Iron added to copper(II) sulfate solution gives:

铁加入硫酸铜(II)溶液会得到：

iron + copper(II) sulfate → copper + iron(II) sulfate

铁 + 硫酸铜(II) → 铜 + 硫酸亚铁

The mark scheme rewards the correct salt name. If iron forms iron(II) sulfate, you should include the ‘(II)’ or say iron(II) sulfate, not just ‘iron sulfate’, because iron has more than one possible ion charge.

评分标准会给正确的盐名称加分。如果铁生成硫酸亚铁，应写出“(II)”或说明是硫酸亚铁，而不是只写“硫酸铁”，因为铁有不止一种可能的离子电荷。

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4. Predicting Reactions Using the Reactivity Series | 利用活动性顺序预测反应

To predict whether a displacement reaction occurs, compare the position of the added metal with the metal already in the salt. If the added metal is higher in the reactivity series, a reaction takes place.

要预测置换反应是否发生，需要比较加入的金属与盐中金属的位置。如果加入的金属在活动性顺序中位置更高，反应就会发生。

If the added metal is lower in the reactivity series, no reaction occurs. The solution remains unchanged because the less reactive metal cannot displace a more reactive metal.

如果加入的金属在活动性顺序中位置更低，则不会发生反应。溶液保持不变，因为较不活泼的金属不能置换较活泼的金属。

For example, copper added to zinc sulfate solution gives no reaction because copper is less reactive than zinc.

例如，铜加入硫酸锌溶液中不会发生反应，因为铜不如锌活泼。

Many mark schemes contain the phrase ‘no reaction’ or ‘no change’ as an acceptable answer. You should also justify it by saying the added metal is less reactive than the metal in the salt.

许多评分标准将“无反应”或“无变化”作为可接受答案。你还应说明原因：加入的金属不如盐中的金属活泼。

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5. Observations That Earn Marks | 能得分的实验现象

Observation questions are very common in CIE displacement reaction papers. You must describe what you see, not what you think is happening at the particle level.

现象题在 CIE 置换反应试卷中非常常见。你必须描述看到的现象，而不是描述粒子层面发生的事情。

For zinc added to blue copper(II) sulfate solution, acceptable observations are:

将锌加入蓝色硫酸铜(II)溶液中，可接受的现象包括：

• The blue colour of the solution fades or becomes paler | 溶液的蓝色变浅或褪去
• A reddish-brown solid forms on the surface of the zinc | 锌表面生成红棕色固体
• The reddish-brown solid is copper | 红棕色固体是铜

Examiners often accept ‘brown’, ‘orange-brown’, or ‘red-brown’ for copper, but ‘rust’ is not correct in this context because rust refers to hydrated iron(III) oxide.

考官通常接受用“棕色”“橙色棕色”或“红棕色”描述铜，但“铁锈”在此语境中不正确，因为铁锈指的是水合氧化铁(III)。

For iron added to copper(II) sulfate solution, the blue colour fades and a brown deposit of copper forms. The solution may become pale green because iron(II) ions enter the solution.

将铁加入硫酸铜(II)溶液中，蓝色变浅并生成棕色铜沉积。溶液可能变为浅绿色，因为铁(II)离子进入溶液。

If no reaction occurs, the mark scheme expects you to state that there is no colour change and no solid deposit, or simply ‘no visible change’.

如果没有反应发生，评分标准要求你写明没有颜色变化、没有固体沉积，或直接写“无明显变化”。

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6. Writing Balanced Symbol Equations | 书写配平的化学方程式

At KS3 CIE level, symbol equations are often worth extra marks or used to support word equations. You should be able to write balanced equations for common displacement reactions.

在 KS3 CIE 水平，化学方程式常作为附加分或用于支持文字表达式。你应能写出常见置换反应的配平方程式。

Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)

锌 + 硫酸铜(II) → 硫酸锌 + 铜

Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)

铁 + 硫酸铜(II) → 硫酸亚铁 + 铜

Mg(s) + ZnSO₄(aq) → MgSO₄(aq) + Zn(s)

镁 + 硫酸锌 → 硫酸镁 + 锌

These equations are already balanced because one metal atom replaces one metal ion. The group ions such as sulfate, SO₄, stay unchanged and can be balanced as a single unit.

这些方程式已经配平，因为一个金属原子取代一个金属离子。像 SO₄ 这样的原子团保持不变，可以作为一个整体来配平。

State symbols show the physical state: (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous solution. CIE mark schemes may ignore state symbols at KS3 unless the question specifically asks for them.

状态符号表示物质状态：(s) 固体，(l) 液体，(g) 气体，(aq) 水溶液。除非题目特别要求，否则 KS3 阶段的 CIE 评分标准可能不要求状态符号。

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7. Ionic Equations: Higher-Tier Mark Points | 离子方程式：高分要点

Although ionic equations are more common at IGCSE level, higher-ability KS3 CIE sets may include them as extension material. The ionic equation focuses only on the particles that change.

尽管离子方程式在 IGCSE 阶段更常见，但能力较强的 KS3 CIE 班级可能将其作为拓展内容。离子方程式只关注发生变化的粒子。

For zinc displacing copper from copper(II) sulfate, the sulfate ions are spectator ions. They appear unchanged on both sides, so they are not included in the ionic equation.

在锌从硫酸铜(II)中置换铜的反应中，硫酸根离子是旁观离子。它们在反应前后保持不变，因此不写入离子方程式。

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

锌 + 铜离子 → 锌离子 + 铜

The mark scheme awards marks for correct charges: Cu²⁺ and Zn²⁺. Losing the charges could lose a mark because the equation would not show that ions are involved.

评分标准会为正确的电荷给分：Cu²⁺ 和 Zn²⁺。漏写电荷可能失分，因为方程式没有体现离子参与反应。

For iron displacing copper, the ionic equation is:

铁置换铜的离子方程式为：

Fe(s) + Cu²⁺(aq) → Fe²⁺(aq) + Cu(s)

铁 + 铜离子 → 亚铁离子 + 铜

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8. Mark Scheme Command Words Explained | 评分标准中的指令词解析

CIE mark schemes use specific command words. Understanding these words tells you how much detail to include and what form your answer should take.

CIE 评分标准使用特定的指令词。理解这些词可以告诉你需要写多少细节，以及答案应采用什么形式。

Command word | 指令词	What the mark scheme wants | 评分标准要求
State | 陈述	Short factual answer, no explanation needed | 简短的事实回答，无需解释
Describe | 描述	Write what you observe or what happens | 写出你观察到的现象或发生的事情
Explain | 解释	Use scientific reasons, not just observations | 使用科学原因，而不仅仅是现象
Predict | 预测	Use reactivity series to say whether a reaction occurs | 利用活动性顺序判断是否发生反应
Write a word equation | 写文字表达式	Use names, not symbols or formulae | 使用名称，不使用符号或化学式
Write a symbol equation | 写化学方程式	Use formulae and balance correctly | 使用化学式并正确配平

For ‘explain’ questions, you must link the observation to the reactivity series. A common mark scheme phrase is: ‘Zinc is more reactive than copper, so zinc displaces copper from the copper(II) sulfate solution.’

对于“解释”类问题，你必须把现象与活动性顺序联系起来。评分标准中常见的表述是：“锌比铜活泼，因此锌从硫酸铜(II)溶液中置换出铜。”

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9. Model Answers for Classic Questions | 经典题型的标准答案

Below are three classic CIE KS3 displacement questions with model answers and mark scheme points. Practise writing these answers under timed conditions.

以下是三道经典的 CIE KS3 置换反应题目，附有标准答案和给分点。请在计时条件下练习书写这些答案。

Question 1

题目 1

A student adds a piece of zinc to blue copper(II) sulfate solution. State two observations.

一名学生将一块锌加入蓝色硫酸铜(II)溶液中。写出两个观察现象。

Model answer:

标准答案：

• The blue colour fades | 蓝色变浅
• A reddish-brown solid forms on the zinc | 锌表面生成红棕色固体

Mark scheme: one mark for colour fade, one mark for the brown or reddish-brown deposit

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