📚 Neutralisation | 中和反应
Neutralisation is the reaction between an acid and a base that produces a salt and water. It is one of the most useful chemical ideas in everyday life, from treating indigestion to improving soil for crops.
中和反应是酸与碱反应生成盐和水的过程。它是日常生活中最有用的化学概念之一，从缓解消化不良到改善农作物土壤都离不开它。
In this revision guide you will learn how to represent neutralisation with word and symbol equations, test pH, name salts, and apply the idea to real contexts.
在这份复习指南中，你将学习如何用文字方程式和符号方程式表示中和反应、检测 pH、命名盐，以及把这一概念应用到实际情境中。
1. What Is Neutralisation? | 什么是中和反应？
Neutralisation is a chemical reaction in which an acid reacts with a base to form a salt and water.
中和反应是酸与碱反应生成盐和水的一种化学反应。
In KS3, the base is often an alkali, which is a soluble base that releases hydroxide ions (OH⁻) in water.
在 KS3 阶段，所说的碱通常是可溶性碱，它在水中会释放出氢氧根离子（OH⁻）。
The general word equation is:
通用文字方程式为：
acid + base → salt + water
For example, hydrochloric acid reacts with sodium hydroxide to make sodium chloride and water.
例如，盐酸与氢氧化钠反应生成氯化钠和水。
The balanced symbol equation for this reaction is:
该反应的配平符号方程式为：
HCl + NaOH → NaCl + H₂O
2. Acids and Bases Quick Recap | 酸与碱快速回顾
Acids have a pH below 7. Common examples include hydrochloric acid, sulfuric acid and citric acid.
酸的 pH 值低于 7。常见的酸包括盐酸、硫酸和柠檬酸。
Bases have a pH above 7. Common bases include sodium hydroxide, calcium carbonate and ammonia solution.
碱的 pH 值高于 7。常见的碱包括氢氧化钠、碳酸钙和氨水。
An alkali is a base that dissolves in water, such as sodium hydroxide solution.
碱是指能溶于水的碱，例如氢氧化钠溶液。
Remember: acids contain hydrogen ions (H⁺), while alkalis contain hydroxide ions (OH⁻).
记住：酸中含有氢离子（H⁺），而碱溶液中含有氢氧根离子（OH⁻）。
3. The General Word Equation | 通用文字方程式
The simplest neutralisation reaction follows this pattern:
最简单的中和反应遵循以下模式：
acid + metal hydroxide → salt + water
This works for many alkalis such as sodium hydroxide, potassium hydroxide and calcium hydroxide.
这适用于许多碱，例如氢氧化钠、氢氧化钾和氢氧化钙。
For metal oxides and metal carbonates, the pattern changes slightly:
对于金属氧化物和金属碳酸盐，规律略有不同：
acid + metal oxide → salt + water
acid + metal carbonate → salt + water + carbon dioxide
Notice that neutralisation with a carbonate also produces carbon dioxide gas, so you will see bubbles.
请注意，碳酸盐参与的中和反应还会产生二氧化碳气体，因此你会看到气泡。
4. pH and Universal Indicator | pH 与通用指示剂
The pH scale runs from 0 to 14. A pH of 7 is neutral, below 7 is acidic, and above 7 is alkaline.
pH 标度的范围是 0 到 14。pH 值为 7 时呈中性，低于 7 为酸性，高于 7 为碱性。
Universal indicator changes colour depending on the pH. The table below shows typical colours.
通用指示剂会根据 pH 值改变颜色。下表显示了典型颜色。
| pH range | pH 范围 | Colour | 颜色 | Meaning | 含义 |
|---|---|---|
| 0-2 | 0-2 | Red | 红色 | Strong acid | 强酸性 |
| 3-4 | 3-4 | Orange | 橙色 | Weak acid | 弱酸性 |
| 5-6 | 5-6 | Yellow | 黄色 | Very weak acid | 极弱酸性 |
| 7 | 7 | Green | 绿色 | Neutral | 中性 |
| 8-9 | 8-9 | Blue | 蓝色 | Weak alkali | 弱碱性 |
| 10-12 | 10-12 | Purple | 紫色 | Strong alkali | 强碱性 |
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