📚 Writing Word Equations | 书写文字方程式
A word equation is a simple way to summarise a chemical reaction using the names of substances. It shows what you start with and what you end with, without needing chemical formulas or symbols.
文字方程式是用物质名称总结化学反应的一种简单方法。它展示你开始用什么、最后得到什么，不需要化学式或符号。
1. What is a Word Equation? | 什么是文字方程式
A word equation describes a chemical reaction in words. For example, when hydrogen gas burns in oxygen, the word equation is:
文字方程式用文字描述化学反应。例如，氢气在氧气中燃烧时，文字方程式为：
hydrogen + oxygen → water
The substances on the left are the reactants, and the substance on the right is the product.
左边是反应物，右边是生成物。
2. Reactants and Products | 反应物与生成物
In any reaction, the substances you start with are called reactants. They are always written on the left of the arrow. The substances that are made are called products and are written on the right of the arrow.
在任何反应中，起始物质称为反应物，始终写在箭头的左边。生成的物质称为生成物，写在箭头的右边。
| Term | 术语 | Meaning | 含义 | Position | 位置 |
|---|---|---|
| Reactant | 反应物 | Starting substance | 起始物质 | Left of arrow | 箭头左侧 |
| Product | 生成物 | New substance made | 生成的新物质 | Right of arrow | 箭头右侧 |
3. The Arrow and Plus Signs | 箭头与加号
The plus sign in a word equation means "and", so it separates two reactants or two products. The arrow means "reacts to form" or "produces". You should not use an equals sign, because a chemical reaction makes new substances rather than showing two things that are the same.
文字方程式中的加号表示“和”，用于分隔两种反应物或两种生成物。箭头表示“反应生成”或“产生”。你不应使用等号，因为化学反应会生成新物质，而不是表示两边相同。
For example, the equation "sodium + chlorine → sodium chloride" is read as "sodium and chlorine react to form sodium chloride".
例如，方程式“钠 + 氯 → 氯化钠”读作“钠和氯反应生成氯化钠”。
4. Using Correct Chemical Names | 使用正确的化学名称
Word equations are only correct if the chemical names are accurate. Common gases include hydrogen, oxygen, carbon dioxide, nitrogen and chlorine. A metal reacting with oxygen usually produces a metal oxide, such as magnesium oxide or copper oxide.
只有化学名称准确，文字方程式才正确。常见气体包括氢气、氧气、二氧化碳、氮气和氯气。金属与氧气反应通常会生成金属氧化物，例如氧化镁或氧化铜。
- magnesium + oxygen → magnesium oxide | 镁 + 氧气 → 氧化镁
- copper + oxygen → copper oxide | 铜 + 氧气 → 氧化铜
- sodium + chlorine → sodium chloride | 钠 + 氯气 → 氯化钠
Always spell the full names correctly. Do not mix symbols such as Na or Cl into a word equation.
始终正确拼写完整名称。不要将 Na 或 Cl 等符号混入文字方程式中。
5. Combustion Reactions | 燃烧反应
Combustion is burning in oxygen. Many substances react with oxygen and release heat and light. When elements burn in oxygen, the product is often an oxide.
燃烧是在氧气中发生的燃烧反应。许多物质与氧气反应并释放热量和光。元素在氧气中燃烧时，产物通常是氧化物。
hydrogen + oxygen → water
magnesium + oxygen → magnesium oxide
Fuels that contain carbon and hydrogen, such as methane, burn in oxygen to produce carbon dioxide and water.
含有碳和氢的燃料，例如甲烷，在氧气中燃烧会生成二氧化碳和水。
methane + oxygen → carbon dioxide + water
6. Metals Reacting with Acids | 金属与酸反应
When a metal reacts with an acid, the products are always a salt and hydrogen gas. The general word equation is:
金属与酸反应时，产物始终是一种盐和氢气。通用的文字方程式为：
metal + acid → salt + hydrogen
For example:
例如：
- magnesium + hydrochloric acid → magnesium chloride + hydrogen | 镁 + 盐酸 → 氯化镁 + 氢气
- zinc + sulfuric acid → zinc sulfate + hydrogen | 锌 + 硫酸 → 硫酸锌 + 氢气
Hydrogen gas can be tested with a burning splint. It produces a squeaky pop sound.
氢气可以用燃烧的木条检验，会发出“咝咝”的爆鸣声。
7. Neutralisation: Acids and Alkalis | 中和反应：酸与碱
When an acid reacts with an alkali, the reaction is called neutralisation. The products are a salt and water. The general word equation is:
酸与碱反应称为中和反应，产物是一种盐和水。通用的文字方程式为：
acid + alkali → salt + water
For example:
例如：
hydrochloric acid + sodium hydroxide → sodium chloride + water
The name of the salt comes from the acid and the alkali. Hydrochloric acid produces chloride salts, and sulfuric acid produces sulfate salts.
盐的名称来自酸和碱。盐酸生成氯化物盐，硫酸生成硫酸盐。
8. Acids Reacting with Carbonates | 酸与碳酸盐反应
When an acid reacts with a carbonate, three products are formed: a salt, water and carbon dioxide gas. The general word equation is:
酸与碳酸盐反应会生成三种产物：盐、水和二氧化碳气体。通用的文字方程式为：
acid + carbonate → salt + water + carbon dioxide
For example:
例如：
hydrochloric acid + calcium carbonate → calcium chloride + water + carbon dioxide
Carbon dioxide gas can be tested by bubbling it through limewater. The limewater turns cloudy.
二氧化碳气体可以通过将其通入石灰水来检验。石灰水会变浑浊。
9. Thermal Decomposition | 热分解
Thermal decomposition is breaking down a compound by heating. Many metal carbonates decompose when heated into a metal oxide and carbon dioxide gas. The general word equation is:
热分解是通过加热使化合物分解。许多金属碳酸盐受热分解为金属氧化物和二氧化碳气体。通用的文字方程式为：
metal carbonate → metal oxide + carbon dioxide
For example:
例如：
copper carbonate → copper oxide + carbon dioxide
Copper carbonate is green, and copper oxide is black. This colour change is a useful observation for thermal decomposition.
碳酸铜是绿色的，氧化铜是黑色的。这一颜色变化是热分解反应的一个有用观察现象。
10. Displacement Reactions | 置换反应
A more reactive metal can displace a less reactive metal from its compound. The general word equation is:
较活泼的金属可以把较不活泼的金属从其化合物中置换出来。通用的文字方程式为：
+ compound of less reactive metal → less reactive metal + compound of more reactive metal
For example, iron is more reactive than copper, so it displaces copper from copper sulfate solution:
例如，铁比铜活泼，因此铁可以从硫酸铜溶液中置换出铜：
iron + copper sulfate → iron sulfate + copper
This links to the reactivity series: a metal higher in the series can displace a metal lower in the series.
这与金属活动性顺序有关：排在活动性顺序中较前的金属可以置换较后的金属。
11. Writing Word Equations from Descriptions | 根据描述书写文字方程式
To write a word equation, follow these steps. First, identify the reactants in the description. Second, identify the products. Third, write the reactants on the left, separated by plus signs, then an arrow, then the products on the right.
书写文字方程式时，请按照以下步骤进行。首先，找出描述中的反应物。其次，找出生成物。第三，将反应物写在左侧，用加号分隔，然后写箭头，最后在右侧写生成物。
Example description: When calcium reacts with hydrochloric acid, calcium chloride and hydrogen are formed.
示例描述：当钙与盐酸反应时，生成氯化钙和氢气。
The word equation is:
文字方程式为：
calcium + hydrochloric acid → calcium chloride + hydrogen
Useful clue words: "reacts with" often means a plus sign, and "forms", "produces" or "makes" often means the arrow.
有用的提示词：“与……反应”通常表示加号，“生成”“产生”或“制得”通常表示箭头。
12. Common Mistakes and Top Tips | 常见错误与高分技巧
When writing word equations at KS3, avoid these common mistakes and follow the tips below.
在KS3阶段书写文字方程式时，避免以下常见错误并遵循以下提示。
- Do not use chemical formulas. Write full names, such as "water", not H₂O. | 不要使用化学式。写出完整名称，如“水”，而不是 H₂O。
- Spell chemical names correctly. For example, write "sulfur" carefully and check names of salts. | 正确拼写化学名称。例如，仔细书写“sulfur”，并检查盐的名称。
- Use an arrow, not an equals sign. A reaction produces new substances. | 使用箭头，不要使用等号。反应会生成新物质。
- Do not add balancing numbers. Word equations do not need numbers in front of names. | 不要添加配平数字。文字方程式不需要在名称前加数字。
- Check patterns. Acid plus carbonate always gives salt, water and carbon dioxide. | 检查反应规律。酸与碳酸盐总是生成盐、水和二氧化碳。
Practice with common reactions, and word equations will become quick and accurate.
多练习常见反应，文字方程式的书写会变得又快又准确。
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