📚 Reactions of Metals with Acids | 金属与酸的反应
When a reactive metal is added to a dilute acid, a chemical reaction takes place. The metal fizzes, hydrogen gas is released, and a salt is formed in solution. This topic is central to KS3 CIE Chemistry and helps explain reactivity, gas tests and salt naming.
当活泼金属加入稀酸时，会发生化学反应。金属会冒泡，放出氢气，溶液中生成盐。这个主题是 KS3 CIE 化学的核心内容，有助于解释金属活动性、气体检验和盐的命名。
1. What Happens When a Metal Meets an Acid? | 金属遇到酸会发生什么？
When a reactive metal such as magnesium or zinc is placed in dilute hydrochloric acid, bubbles of gas form quickly on the surface of the metal. The metal gradually becomes smaller and may appear to dissolve, while the solution often becomes warm because the reaction gives out heat energy.
当镁或锌等活泼金属放入稀盐酸中时，金属表面会迅速产生气泡。金属逐渐变小，看起来像溶解了，同时溶液通常会变热，因为反应会放出热能。
- Bubbles of hydrogen gas are produced. 产生氢气气泡。
- The metal decreases in size. 金属体积减小。
- The mixture may become warmer. 混合物可能变热。
- A colourless or coloured salt solution forms. 形成无色或有色盐溶液。
These observations show that a new substance has been made. The gas can be collected and tested, and the dissolved salt can be recovered by evaporation.
这些观察表明已经生成了新物质。可以收集并检验气体，还可以通过蒸发回收溶解的盐。
2. The General Word Equation | 一般文字方程式
All reactions between a reactive metal and a dilute acid follow the same pattern. The metal replaces hydrogen in the acid, producing a salt and hydrogen gas.
所有活泼金属与稀酸的反应都遵循相同的模式。金属取代酸中的氢，生成盐和氢气。
metal + acid → salt + hydrogen
金属 + 酸 → 盐 + 氢气
For example, magnesium reacts with hydrochloric acid to make magnesium chloride and hydrogen. This general equation is very useful because it allows you to predict the products of many different metal-acid reactions.
例如，镁与盐酸反应生成氯化镁和氢气。这个通式非常有用，因为它可以帮助你预测许多不同金属与酸反应的产物。
3. Naming the Salt | 盐的命名
The name of the salt depends on two things: the metal used and the acid used. The first part of the salt name comes from the metal, and the second part comes from the acid.
盐的名称取决于两个因素：所用的金属和所用的酸。盐名称的前半部分来自金属，后半部分来自酸。
Hydrochloric acid always makes chloride salts. Sulfuric acid always makes sulfate salts. Nitric acid always makes nitrate salts.
盐酸总是生成氯化物盐。硫酸总是生成硫酸盐。硝酸总是生成硝酸盐。
| Acid 酸 | Salt ending 盐名称结尾 | Example 示例 |
| Hydrochloric acid 盐酸 | -chloride 氯化物 | Zinc chloride 氯化锌 |
| Sulfuric acid 硫酸 | -sulfate 硫酸盐 | Magnesium sulfate 硫酸镁 |
| Nitric acid 硝酸 | -nitrate 硝酸盐 | Iron nitrate 硝酸铁 |
If the metal has more than one possible ion charge, such as iron, the salt name may include a Roman numeral in later study. At KS3, you simply need to know the main salt endings.
如果金属有不止一种可能的离子电荷，例如铁，盐的名称在高年级学习时可能需要加罗马数字。在 KS3 阶段，你只需要掌握主要的盐名称结尾。
4. Testing for Hydrogen Gas | 氢气的检验
Hydrogen gas is colourless and odourless, so you cannot see or smell it directly. The standard test is to hold a lighted splint at the mouth of the test tube containing the gas.
氢气是无色无味的气体，所以无法直接看到或闻到。标准的检验方法是将一根点燃的木条放在装有气体的试管口。
If hydrogen is present, it burns rapidly with a distinctive squeaky pop sound. This happens because hydrogen is very flammable and mixes quickly with air before igniting.
如果存在氢气，它会快速燃烧，发出独特的“噗”的爆鸣声。这是因为氢气非常易燃，在点燃前会迅速与空气混合。
- Use a lighted splint, not a glowing splint. 使用点燃的木条，而不是带火星的木条。
- Hold the splint at the open mouth of the tube. 将木条放在试管开口处。
- A positive result is a squeaky pop. 正结果是发出“噗”的爆鸣声。
- This test is safe only for small volumes of hydrogen. 该检验只适用于少量氢气。
Do not allow large amounts of hydrogen to build up near a flame, because hydrogen-air mixtures can explode strongly.
不要让大量氢气在火焰附近积聚，因为氢气与空气的混合物可能发生剧烈爆炸。
5. The Reactivity Series and Acid Reactions | 金属活动性顺序与酸反应
Different metals react with dilute acids at different speeds. More reactive metals react more vigorously, producing bubbles faster and releasing more heat in the same time.
不同的金属与稀酸反应的速度不同。越活泼的金属反应越剧烈，产生气泡更快，在相同时间内放出的热量也更多。
Potassium, sodium and lithium are extremely reactive and too dangerous for school experiments. In the laboratory, magnesium, zinc and iron are commonly tested with dilute hydrochloric acid or sulfuric acid.
钾、钠和锂极其活泼，在学校实验中太危险。实验室中常用镁、锌和铁与稀盐酸或稀硫酸进行试验。
- Magnesium reacts very vigorously with rapid bubbles. 镁反应非常剧烈，气泡很快。
- Zinc reacts steadily with a moderate rate. 锌反应平稳，速率中等。
- Iron reacts slowly, especially when the acid is cold. 铁反应缓慢，尤其是在酸冷的时候。
- Copper does not react with dilute hydrochloric or sulfuric acid. 铜不与稀盐酸或稀硫酸反应。
This pattern helps scientists place metals in order of reactivity, called the reactivity series.
这种规律帮助科学家将金属按活泼性排序，称为金属活动性顺序。
6. Why Copper Does Not React with Dilute Acids | 为什么铜不与稀酸反应
Copper is below hydrogen in the reactivity series. This means copper is less reactive than hydrogen, so it cannot displace hydrogen from an acid.
铜在金属活动性顺序中位于氢之后。这意味着铜的活泼性比氢弱，因此不能从酸中置换出氢。
When copper is added to dilute hydrochloric acid or dilute sulfuric acid, no bubbles form and no copper salt solution is produced. The copper remains unchanged.
当铜加入稀盐酸或稀硫酸时，不会产生气泡，也不会生成铜盐溶液。铜保持不变。
copper + hydrochloric acid → no reaction
铜 + 盐酸 → 不反应
However, copper can react with concentrated nitric acid under special conditions, but that is not part of the KS3 CIE course. At this level, remember that copper does not react with dilute acids that release hydrogen.
然而，铜在特殊条件下可以与浓硝酸反应，但这不属于 KS3 CIE 课程内容。在这个阶段，请记住铜不与释放氢气的稀酸反应。
7. Symbol Equations | 化学方程式
Word equations describe the reactants and products using names. Symbol equations use chemical formulae and must be balanced so that the number of atoms of each element is the same on both sides.
文字方程式用名称描述反应物和产物。化学方程式使用化学式，并且必须配平，使每种元素的原子数在两边相等。
For example, magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen. The balanced symbol equation is shown below.
例如，镁与盐酸反应生成氯化镁和氢气。配平后的化学方程式如下所示。
Mg + 2HCl → MgCl₂ + H₂
镁 + 盐酸 → 氯化镁 + 氢气
Other common examples include zinc reacting with sulfuric acid, and iron reacting with hydrochloric acid:
其他常见例子包括锌与硫酸反应，以及铁与盐酸反应：
Zn + H₂SO₄ → ZnSO₄ + H₂
锌 + 硫酸 → 硫酸锌 + 氢气
Fe + 2HCl → FeCl₂ + H₂
铁 + 盐酸 → 氯化亚铁 + 氢气
Notice that hydrogen is always written as H₂ because hydrogen gas exists as diatomic molecules.
注意氢气总是写成 H₂，因为氢气以双原子分子存在。
8. Observing Rates of Reaction | 观察反应速率
The rate of reaction can be compared by observing how quickly hydrogen gas is produced. One method is to collect the gas in a measuring cylinder or gas syringe and record the volume at regular time intervals.
可以通过观察氢气产生的快慢来比较反应速率。一种方法是用量筒或气体注射器收集气体，并每隔一定时间记录体积。
Another simple method is to count the number of bubbles released in a fixed time, but this is less accurate because bubble size may vary.
另一种简单方法是数一数固定时间内放出的气泡数量，但这种方法不够准确，因为气泡大小可能有差异。
- Keep the acid concentration the same. 保持酸浓度相同。
- Keep the volume of acid the same. 保持酸体积相同。
- Use the same mass and surface area of each metal. 使用相同质量和表面积的每种金属。
- Measure the time taken for a fixed volume of gas to be collected. 测量收集一定体积气体所需的时间。
Magnesium usually produces the same volume of hydrogen in the shortest time, so it has the fastest observable reaction among common school metals.
镁通常在最短时间内产生相同体积的氢气，因此在常见学校金属中，它的可观察反应最快。
9. Salt Solutions and Evaporation | 盐溶液与蒸发结晶
After the metal has reacted completely, the mixture contains a salt dissolved in water. The salt can be separated by gently heating the solution to evaporate the water.
当金属完全反应后，混合物中含有溶解在水中的盐。可以通过缓慢加热溶液蒸发水分来分离出盐。
If a salt solution is heated too strongly, some salts may spit or decompose. In the school laboratory, gentle evaporation using a water bath or low flame is safer.
如果盐溶液加热过猛，某些盐可能会飞溅或分解。在学校实验室中，使用水浴或小火缓慢蒸发更安全。
- Filter the mixture to remove any unreacted metal. 过滤混合物以除去未反应的金属。
- Place the clear salt solution in an evaporating dish. 将澄清的盐溶液放入蒸发皿中。
- Heat gently until crystals begin to form. 缓慢加热，直到开始出现晶体。
- Leave the rest to cool so that larger crystals develop. 其余部分冷却，使晶体长大。
This method is also used to prepare salts such as magnesium sulfate and zinc chloride.
这种方法也用于制备硫酸镁和氯化锌等盐。
10. Metal-Acid Reactions and Neutralisation | 金属与酸的反应和中和反应
Metal-acid reactions are not usually classified as neutralisation reactions. Neutralisation typically produces a salt and water, while metal-acid reactions produce a salt and hydrogen gas.
金属与酸的反应通常不属于中和反应。中和反应通常生成盐和水，而金属与酸的反应生成盐和氢气。
However, both types of reaction use up an acid and form a salt. The key difference is the other product: water in neutralisation, hydrogen in a metal-acid reaction.
但两类反应都会消耗酸并生成盐。关键区别在于另一种产物：中和反应生成水，金属与酸的反应生成氢气。
| Reaction type 反应类型 | Products 产物 |
| Metal + acid 金属 + 酸 | Salt + hydrogen 盐 + 氢气 |
| Metal oxide + acid 金属氧化物 + 酸 | Salt + water 盐 + 水 |
| Metal carbonate + acid 金属碳酸盐 + 酸 | Salt + water + carbon dioxide 盐 + 水 + 二氧化碳 |
Understanding this difference helps you answer questions correctly and predict products in CIE assessments.
理解这一区别有助于你正确回答问题，并在 CIE 考试中预测产物。
11. Safety in the Laboratory | 实验室安全
Metal-acid reactions can be vigorous, especially with magnesium or more reactive metals. Always follow safety rules to prevent accidents.
金属与酸的反应可能很剧烈，尤其是镁或更活泼的金属。务必遵守安全规则，防止事故发生。
- Wear eye protection at all times. 始终佩戴护目镜。
- Use dilute acids as directed by your teacher. 按照老师的指示使用稀酸。
- Keep the reaction mixture away from open flames. 使反应混合物远离明火。
- Do not seal the test tube because hydrogen pressure can build up. 不要密封试管，因为氢气压力会升高。
- Clean up spills immediately with plenty of water. 立即用大量水清理泄漏物。
Hydrogen gas is extremely flammable. Only test small amounts with a lighted splint and follow the teacher's instructions carefully.
氢气极易燃。只应用点燃的木条检验少量氢气，并认真遵循老师的指导。
12. Common Misconceptions | 常见误区
Many students think that all metals react with all acids, but this is false. Metals below hydrogen in the reactivity series, such as copper, do not react with dilute hydrochloric or sulfuric acid.
许多学生认为所有金属都能与所有酸反应，但这是错误的。活动性顺序在氢之后的金属（如铜）不与稀盐酸或稀硫酸反应。
Another misconception is that the acid disappears completely during the reaction. In fact, the acid is used up chemically, and its hydrogen ions are displaced to form hydrogen gas, while the remaining ions form a salt.
另一个误区是认为酸在反应中完全消失了。实际上，酸是被化学消耗了，其氢离子被置换形成氢气，而剩余的离子形成盐。
- Not all metals react with dilute acids. 并非所有金属都与稀酸反应。
- Hydrogen gas is formed, not oxygen. 生成的是氢气，不是氧气。
- The salt remains dissolved in the solution. 盐溶解在溶液中。
- A squeaky pop test must use a lighted splint, not a glowing one. 爆鸣检验必须用点燃的木条，而不是带火星的木条。
Avoiding these errors will help you gain marks in CIE KS3 questions on metal-acid reactions.
避免这些错误将帮助你在 CIE KS3 金属与酸反应题目中得分。
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