Reaction Mechanisms for IGCSE WJEC Chemistry: Essential Exam Notes | IGCSE WJEC 化学：反应机理 考点精讲

📚 Reaction Mechanisms for IGCSE WJEC Chemistry: Essential Exam Notes | IGCSE WJEC 化学：反应机理 考点精讲

In IGCSE WJEC Chemistry, understanding how and why chemical reactions occur is a fundamental skill. The topic of reaction mechanisms focuses on the particle-level explanations for the speed of reactions, known as reaction rates. This article breaks down the key concepts of collision theory, activation energy, and the factors affecting reaction rates, providing you with clear explanations, diagrams, and exam tips to help you succeed.

在IGCSE WJEC 化学中，理解化学反应如何发生以及为何发生是一项基本技能。反应机理这一主题重点从粒子层面解释反应速率，也就是反应速度。本文解析了碰撞理论、活化能以及影响反应速率的因素等关键概念，为你提供清晰的解释、图表和考试技巧，帮助你取得成功。

1. Collision Theory | 碰撞理论

Chemical reactions occur when reactant particles collide with sufficient energy and with the correct orientation. This is the essence of collision theory. Not every collision leads to a reaction; only those that meet the energy and orientation requirements are ‘successful collisions’.

化学反应发生的前提是反应物粒子以足够的能量和正确的取向发生碰撞。这是碰撞理论的核心。并非每次碰撞都会导致反应；只有同时满足能量和取向要求的碰撞才是“有效碰撞”。

For a reaction to take place, the colliding particles must overcome the activation energy barrier. They must also collide in a way that allows bonds to break and new bonds to form. Think of it as a key fitting into a lock: the orientation must be right for a successful reaction.

要发生反应，碰撞的粒子必须克服活化能垒。它们还必须以能够使化学键断裂并形成新键的方式碰撞。可以想象成一把钥匙开一把锁：取向必须正确才能成功反应。

Increasing the number of successful collisions per unit time increases the rate of reaction. Thus, any factor that increases the frequency of collisions or the proportion of particles with energy greater than the activation energy will speed up the reaction.

增加单位时间内有效碰撞的次数会提高反应速率。因此，任何能增加碰撞频率或增加能量超过活化能的粒子比例的因素都会加快反应。

2. Activation Energy | 活化能

Activation energy (Eₙ) is the minimum amount of energy that colliding particles must have in order to react. It is the energy required to break the existing bonds in the reactants and start the reaction. Even exothermic reactions, which release energy overall, need an initial input of activation energy to get started.

活化能（Eₙ）是碰撞粒子发生反应所必须具有的最低能量。它是断裂反应物中现有化学键并启动反应所需的能量。即使是总体上释放能量的放热反应，也需要初始的活化能才能开始。

The magnitude of the activation energy determines how easy it is for a reaction to occur. Reactions with low Eₙ tend to be fast at room temperature, while those with high Eₙ are slow unless energy is supplied (e.g., by heating).

活化能的大小决定了反应发生的难易程度。活化能低的反应在室温下往往很快，而活化能高的反应除非提供能量（例如加热），否则很慢。

In an energy profile diagram, the activation energy is shown as the energy difference between the reactants and the peak of the energy curve (the transition state). Catalysts provide an alternative pathway with a lower activation energy.

在能量变化图中，活化能表示为反应物与能量曲线峰值（过渡态）之间的能量差。催化剂提供了一条活化能较低的替代路径。

3. Effect of Concentration on Reaction Rate |

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

更多咨询请联系16621398022（同微信）