Reactivity Series and Displacement Reactions | 反应性序列与置换反应

📚 Reactivity Series and Displacement Reactions | 反应性序列与置换反应

The reactivity series is one of the cornerstones of IGCSE Edexcel Science – particularly Chemistry – and it unlocks the ability to predict how metals behave in chemical reactions. From the violent fizz of potassium in water to the quiet stability of gold, the order of reactivity explains patterns in extraction, corrosion, and laboratory displacement reactions. This comprehensive revision guide aligns precisely with the Edexcel specification, walking you through definitions, ion–electron half-equations, experimental observations, and common exam pitfalls. A strong command of the topic will support not only your paper-based questions but also any practical assessments you encounter.

反应性序列是IGCSE Edexcel科学（尤其是化学）的基石之一，它能帮你预测金属在化学反应中的表现。从钾与水剧烈嘶嘶作响到金的稳定惰性，反应性顺序揭示了金属提取、腐蚀和实验室置换反应的规律。这份全面复习指南与Edexcel考纲严格同步，带你梳理定义、电子–离子半方程、实验观察和常见考试陷阱。掌握该主题不仅能帮你应对卷面题目，也能为任何实验考核提供有力支撑。

1. Introduction to the Reactivity Series | 反应性序列简介

The reactivity series ranks metals according to how easily they lose outer electrons to form positive ions. A metal that is more reactive acts as a stronger reducing agent, meaning it donates electrons more readily and is more vigorous in reactions with water, acids, or salt solutions. This hierarchical list is constructed from experimental evidence, and its position determines whether a metal can displace another from a compound. In IGCSE Edexcel, you are required to recall the order, justify it with practical observations, and apply it to novel situations.

反应性序列根据金属失去外层电子、形成阳离子的难易程度进行排序。活泼性更强的金属是更强的还原剂，意味着它更容易给出电子，在与水、酸或盐溶液反应时也更剧烈。这一层级分明的列表建立在实验证据之上，而金属所处的位次决定了它能否将另一种金属从化合物中置换出来。Edexcel IGCSE 要求你能够记诵这个顺序，用实验观察来证明它，并将其迁移到新情景中。

2. The Order of Reactivity | 反应性顺序

The full reactivity sequence, including the non-metals carbon and hydrogen, runs from most reactive to least reactive: potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), aluminium (Al), carbon (C), zinc (Zn), iron (Fe), tin (Sn), lead (Pb), hydrogen (H), copper (Cu), silver (Ag), gold (Au), platinum (Pt). Carbon and hydrogen are inserted because they play vital roles as reducing agents in metal extraction; their positions allow you to deduce whether a metal oxide can be reduced by carbon or whether a metal will react with an acid. Edexcel candidates are expected to recall this series accurately and use it to make predictions.

完整的反应性序列（包含非金属碳和氢气）从最活泼到最不活泼依次为：钾（K）、钠（Na）、钙（Ca）、镁（Mg）、铝（Al）、碳（C）、锌（Zn）、铁（Fe）、锡（Sn）、铅（Pb）、氢（H）、铜（Cu）、银（Ag）、金（Au）、铂（Pt）。碳和氢气被纳入序列是因为它们在金属提取中起着关键还原剂的作用；它们所处的位置可以用来推断金属氧化物能否被碳还原，或者一种金属是否会与酸反应。Edexcel 考生需要准确记诵这一序列并能应用于预测。

The table above summarises the observable differences when metals are placed in water and dilute hydrochloric acid. Use these patterns to reason why some metals are extracted by electrolysis while others can be smelted with carbon.

上表总结了金属放入水和稀盐酸时可观察到的差异。你可以利用这些模式来解释为什么有些金属通过电解法提取，而另一些则可用碳冶炼。

3. Memorising the Reactivity Series (Mnemonics) | 记忆反应性序列（助记法）

A popular mnemonic used in Edexcel classrooms is: “Please Stop Calling Me A Cute Zebra I Think Lions Hunt Cute Silver Goldfish” – the initial letters stand for Potassium, Sodium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Tin, Lead, Hydrogen, Copper, Silver, Gold. For Chinese learners, a rhythmic phrase like “钾钠钙镁铝碳锌铁锡铅氢铜银金” (jiǎ nà gài měi lǚ tàn xīn tiě xí qiān qīng tóng yín jīn) can be sung to the tune of a children’s song. Whichever memory aid you choose, daily repetition and writing out the order from memory will cement the sequence before the exam.

Edexcel 课堂上常用的一句英文助记法是：“Please Stop Calling Me A Cute Zebra I Think Lions Hunt Cute Silver Goldfish”——每个单词的首字母代表钾、钠、钙、镁、铝、碳、锌、铁、锡、铅、氢、铜、银、金。对于中文学习者，一句顺口溜“钾钠钙镁铝碳锌铁锡铅氢铜银金”也能帮助快速记忆。无论你选择哪种记忆术，每天重复并默写顺序都能在考前牢固掌握该序列。

4. Reactions of Metals with Water and Acids | 金属与水和酸的反应

Metals above hydrogen in the reactivity series can displace hydrogen gas from dilute acids. For example, magnesium ribbon placed in dilute hydrochloric acid fizzes rapidly: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g). Similarly, zinc reacts with dilute sulfuric acid: Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g). The most reactive metals – potassium, sodium and calcium – react vigorously with cold water: 2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g), 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g), Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g). Magnesium reacts extremely slowly with cold water but more readily with steam. Aluminium, zinc, iron and lead do not react with cold water but will do so with steam, producing a metal oxide and hydrogen – a reaction less frequently examined at IGCSE. Metals below hydrogen, such as copper, silver and gold, fail to react with dilute acids, which is why copper residues are often found in archaeological coins.

序列中位于氢之上的金属可以从稀酸中置换出氢气。例如，镁带放入稀盐酸会迅速冒出气泡：Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)。同样，锌与稀硫酸反应：Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)。最活泼的金属——钾、钠和钙——与冷水剧烈反应：2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g)、2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)、Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)。镁与冷水反应极慢，但能与水蒸气较快反应。铝、锌、铁和铅不与冷水反应，但能与蒸汽反应生成金属氧化物和氢气——IGCSE 较少考察该反应。位于氢以下的金属，如铜、银和金，不与稀酸反应，这也是考古币上常有铜残留的原因。

5. Displacement Reactions Defined | 置换反应定义

A displacement reaction is a chemical change in which a more reactive element takes the place of a less reactive element in a compound. In the context of the reactivity series, a metal higher up in the series can displace a metal lower down from its salt solution or oxide. The driving force is the stronger tendency of the more reactive metal to lose electrons and form ions. Displacement reactions are always redox processes: the more reactive metal is oxidised (loses electrons), while the less reactive metal ion is reduced (gains electrons).

置换反应是指一种更活泼的元素将化合物中较不活泼的元素替代出来的化学变化。在反应性序列的情境里，位次较高的金属可以把位次较低的金属从其盐溶液或氧化物中置换出来。其驱动力是活泼金属更强的失去电子、形成离子的倾向。置换反应总是氧化还原过程：活泼金属被氧化（失去电子），而较不活泼的金属离子被还原（得到电子）。

6. Displacement Reactions with Metal Salt Solutions | 金属与盐溶液的置换反应

A classic classroom demonstration is placing a strip of zinc into blue copper(II) sulfate solution. The zinc dissolves and the blue colour fades while a reddish-brown deposit of copper metal appears: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s). At the ionic level the reaction is simpler: zinc atoms donate electrons to copper(II) ions: Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s). Similarly, an iron nail dipped in copper sulfate becomes coated with copper and the solution turns pale green due to Fe²⁺ ions:

Published by TutorHao | IGCSE Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）