📚 Catalysts | 催化
Catalysts play a vital role in controlling the rate of chemical reactions, both in living systems and in industrial processes. In GCSE CCEA Chemistry, understanding how catalysts work, their characteristics, and their applications is essential for linking theory to real-world chemistry. This revision guide covers all the key points you need, with clear explanations and examples.
催化剂在控制化学反应速率方面起着至关重要的作用，无论是在生命系统还是工业过程中。在 GCSE CCEA 化学中，理解催化剂的工作原理、特性及其应用，对于将理论与实际化学联系起来至关重要。本篇复习指南涵盖了你需要掌握的所有要点，并辅以清晰的解释和实例。
1. What Are Catalysts? | 什么是催化剂？
A catalyst is a substance that increases the rate of a chemical reaction without being used up or permanently changed by the reaction. It provides an alternative reaction pathway with a lower activation energy, allowing more particles to have sufficient energy to react.
催化剂是一种能够提高化学反应速率而自身在反应中不被消耗或永久改变的物质。它提供了一条活化能较低的替代反应路径，使更多粒子具有足够的能量发生反应。
Examples include manganese(IV) oxide (MnO₂) in the decomposition of hydrogen peroxide, iron in the Haber process, and platinum in catalytic converters.
例如，过氧化氢分解中的二氧化锰 (MnO₂)、哈伯法中的铁，以及催化转化器中的铂。
2. How Catalysts Work – Activation Energy | 催化剂如何工作——活化能
For a reaction to occur, colliding particles must possess a minimum amount of energy, known as the activation energy (Ea). A catalyst lowers this activation energy, meaning that a greater proportion of particles now have energy equal to or greater than the new, lower Ea. This increases the frequency of successful collisions, thereby speeding up the reaction.
反应要发生，碰撞的粒子必须具有最小能量，即活化能 (Ea)。催化剂降低了这一活化能，意味着现在有更多比例粒子的能量等于或高于新的较低活化能。这就增加了有效碰撞的频率，从而加快了反应速率。
It is crucial to note that a catalyst does not change the energy of the reactants or products, so the overall enthalpy change (ΔH) remains the same.
需要注意的是，催化剂不改变反应物或产物的能量，因此总焓变 (ΔH) 保持不变。
3. Energy Profile Diagrams for Catalysed Reactions | 催化反应的能量分布图
An energy profile diagram shows the energy changes during a reaction. For an uncatalysed exothermic reaction, the curve rises from reactants to a high peak (the transition state) and then falls to products. With a catalyst, the peak is much lower. The activation energy for the catalysed pathway is smaller, but the starting and ending energy levels are identical.
能量分布图展示了反应过程中的能量变化。对于未催化的放热反应，曲线从反应物上升到较高的峰（过渡态），然后下降到产物。有催化剂时，峰要低得多。催化路径的活化能较小，但起点和终点的能量水平完全相同。
Ea (uncatalysed) > Ea (catalysed) ; ΔH unchanged
You can draw these diagrams by labelling the reactants, products, activation energies (with and without catalyst), and ΔH. Be careful to show the catalysed route as a dotted curve below the original peak.
你可以通过标记反应物、产物、活化能（有催化剂和无催化剂）以及 ΔH 来绘制这些图。注意将催化路线画为原峰下方的一条虚线曲线。
4. Characteristics of Catalysts | 催化剂的特性
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