📚 The Reactions of Metals with Oxygen | 金属与氧气的反应
Many metals react with oxygen in the air. Some reactions are fast and dramatic, such as magnesium burning with a bright white flame. Other reactions are slow, such as iron rusting over many days or weeks. In every case, the metal combines with oxygen to form a metal oxide. Understanding these reactions helps us explain why metals corrode, why some metals need protection, and why others stay shiny for years.
许多金属会与空气中的氧气发生反应。有些反应快速而剧烈，例如镁燃烧时发出耀眼的白光。另一些反应则很缓慢，例如铁在数天或数周内生锈。无论快慢，金属都会与氧气结合生成金属氧化物。理解这些反应有助于我们解释金属为什么会腐蚀、为什么有些金属需要保护，以及为什么另一些金属可以多年保持光亮。
1. What Is Oxidation? | 什么是氧化？
When a metal reacts with oxygen, the process is called oxidation. Oxidation is a chemical reaction in which a substance gains oxygen. Many metals react with oxygen in the air to form metal oxides.
当金属与氧气反应时，这个过程叫做氧化。氧化是一种物质获得氧的化学反应。许多金属会与空气中的氧气反应生成金属氧化物。
Oxidation does not only happen in burning. Slow oxidation, such as the rusting of iron, also involves oxygen. The product of a metal reacting with oxygen is always a metal oxide.
氧化不仅发生在燃烧中。缓慢氧化（例如铁生锈）也涉及氧气。金属与氧气反应的产物始终是金属氧化物。
2. The General Word Equation | 通用文字方程式
The reaction between a metal and oxygen can be written as a simple word equation:
金属与氧气之间的反应可以写成一个简单的文字方程式：
metal + oxygen → metal oxide
This word equation shows that a metal and oxygen are the reactants, while the metal oxide is the product. For example, magnesium and oxygen react to form magnesium oxide.
这个文字方程式表明金属和氧气是反应物，而金属氧化物是生成物。例如，镁和氧气反应生成氧化镁。
Word equations are useful because they use the names of substances instead of chemical formulas. This helps us see the pattern in many different reactions.
文字方程式很有用，因为它们使用物质名称而不是化学式。这有助于我们看到许多不同反应中的规律。
3. Burning Magnesium in Air | 镁在空气中燃烧
Magnesium burns in air with a brilliant white flame. This reaction releases a large amount of heat and light energy. The white powder produced is magnesium oxide.
镁在空气中燃烧时产生耀眼的白光。这个反应释放大量的热能和光能。生成的白色粉末是氧化镁。
2Mg + O₂ → 2MgO
Before the reaction, magnesium is a shiny grey metal. After burning, the magnesium oxide is a dull white solid. The change in appearance is evidence that a new substance has formed.
反应前，镁是一种有光泽的灰色金属。燃烧后，氧化镁是一种暗白色的固体。外观的变化证明生成了新物质。
Safety note: you should never look directly at burning magnesium because the intense light can damage your eyes. A blue cobalt glass filter or indirect viewing is used in the laboratory.
安全提示：切勿直接注视燃烧的镁，因为强烈的光会损伤眼睛。实验室中会使用蓝色钴玻璃滤光片或间接观察。
4. Iron Reacts with Oxygen: Rusting | 铁与氧气反应：生锈
Iron reacts slowly with oxygen in the air to form rust. Rust is a flaky, reddish-brown solid. The chemical name for common rust is hydrated iron(III) oxide.
铁会与空气中的氧气缓慢反应生成锈。锈是一种片状的红棕色固体。常见锈的化学名称是水合氧化铁(III)。
Rusting requires both oxygen and water. If iron is kept completely dry or in an oxygen-free environment, it does not rust. That is why iron tools left outside in damp air rust much faster.
生锈需要氧气和水。如果铁保持完全干燥或处于无氧环境中，它就不会生锈。这就是为什么放在室外潮湿空气中的铁制工具会更快生锈。
The word equation for rusting is usually simplified as:
生锈的文字方程式通常简化为：
iron + oxygen + water → hydrated iron(III) oxide
Unlike magnesium burning, rusting is a slow oxidation. It does not produce a bright flame, but it still changes iron into a new substance with different properties.
与镁的燃烧不同，生锈是一种缓慢的氧化。它不会产生明亮的火焰，但仍然把铁变成具有不同性质的新物质。
5. Copper and Oxygen: Forming Copper Oxide | 铜与氧气：生成氧化铜
Copper does not burn with a flame as easily as magnesium. However, when copper is heated strongly in air, its surface turns black. The black substance is copper(II) oxide.
铜不像镁那样容易燃烧产生火焰。但是，当铜在空气中被强热时，其表面会变黑。这种黑色物质是氧化铜(II)。
2Cu + O₂ → 2CuO
Before heating, copper is a shiny orange-brown metal. After heating, the black copper oxide coating can be seen clearly. This is another example of oxidation.
加热前，铜是一种有光泽的橙棕色金属。加热后，可以清楚地看到黑色的氧化铜表层。这是氧化的另一个例子。
If the black copper oxide is scraped off, shiny copper may be exposed underneath. This tells us that only the surface layer has reacted with oxygen.
如果刮掉黑色的氧化铜，下面可能会露出有光泽的铜。这告诉我们只有表层与氧气发生了反应。
6. Aluminium and Its Protective Oxide Layer | 铝及其保护性氧化层
Aluminium is a reactive metal, but it often appears unreactive. This is because aluminium reacts quickly with oxygen to form a very thin, tightly bonded layer of aluminium oxide on its surface.
铝是一种活泼金属，但它往往看起来不活泼。这是因为铝会迅速与氧气反应，在其表面形成一层非常薄且结合紧密的氧化铝层。
This aluminium oxide layer is tough and prevents oxygen from reaching the aluminium underneath. As a result, aluminium objects do not corrode easily in everyday use.
这层氧化铝很坚固，能阻止氧气接触下面的铝。因此，铝制品在日常使用中不易腐蚀。
This is different from rusting. Rust is flaky and falls away, exposing more iron to oxygen. Aluminium oxide stays in place and protects the metal.
这与生锈不同。锈是片状的，会脱落，使更多的铁暴露在氧气中。氧化铝则保持在原位并保护金属。
7. Comparing Reactivity of Metals with Oxygen | 比较金属与氧气的反应性
Different metals react with oxygen at different speeds and with different amounts of energy released. We can use these observations to compare metal reactivity.
不同的金属与氧气反应的速度不同，释放的能量也不同。我们可以利用这些观察结果来比较金属的反应性。
| Metal | Observation with oxygen | Reactivity |
|---|---|---|
| Magnesium | Burns vigorously with a bright white flame | High |
| Zinc | Burns less vigorously; forms yellow oxide when hot | Medium |
| Iron | Reacts slowly; rusts over time | Low-medium |
| Copper | Does not burn; forms black oxide when heated | Low |
| Gold | Does not react with oxygen | Very low |
From the table, we can see that magnesium is more reactive than copper because magnesium reacts much faster and more violently with oxygen.
从表中可以看出，镁比铜更活泼，因为镁与氧气的反应更快、更剧烈。
8. Oxidation as a Chemical Change | 氧化是一种化学变化
Oxidation is a chemical change, not a physical change. In a chemical change, new substances are formed and the change is usually difficult to reverse.
氧化是一种化学变化，而不是物理变化。在化学变化中，会生成新物质，而且这种变化通常难以逆转。
For example, when magnesium burns, the shiny grey metal and colourless oxygen gas disappear. A white solid, magnesium oxide, is produced. This new substance has different properties from the reactants.
例如，当镁燃烧时，有光泽的灰色金属和无色的氧气消失了，生成了一种白色固体——氧化镁。这种新物质具有与反应物不同的性质。
Evidence of a chemical change includes a colour change, the release of heat or light, or the formation of a new solid. Burning magnesium shows all of these signs.
化学变化的证据包括颜色变化、释放热或光，或生成新的固体。镁的燃烧表现出所有这些迹象。
9. Conservation of Mass in Oxidation | 氧化中的质量守恒
When a metal burns or rusts, the metal oxide produced has a greater mass than the original metal. This is because oxygen atoms from the air are added to the metal.
当金属燃烧或生锈时，生成的金属氧化物质量比原来的金属大。这是因为空气中的氧原子加入到了金属中。
In a closed container, the total mass before and after the reaction stays the same. Oxygen gas is one of the reactants, so its mass is already included in the total mass of the system.
在密闭容器中，反应前后的总质量保持不变。氧气是反应物之一，因此它的质量已经包含在系统的总质量中。
This is the law of conservation of mass: mass is never created or destroyed in a chemical reaction. Atoms are simply rearranged to form new substances.
这就是质量守恒定律：在化学反应中质量不会被创造或消灭。原子只是重新排列形成新物质。
10. Preventing Rust and Oxidation | 防止生锈和氧化
We can slow down or prevent rusting by keeping oxygen or water away from iron. Common methods include painting, oiling, and coating with plastic.
我们可以通过使氧气或水远离铁来减缓或防止生锈。常见的方法包括涂漆、涂油和塑料涂层。
Another method is galvanising, where iron is coated with a layer of zinc. Zinc acts as a barrier and also reacts with oxygen more readily than iron, protecting the iron even if the coating is scratched.
另一种方法是镀锌，即在铁表面镀一层锌。锌起到屏障作用，而且比铁更容易与氧气反应，即使涂层被划伤也能保护铁。
For aluminium, no special protection is usually needed because its natural oxide layer already prevents further corrosion. This is why aluminium is used for window frames and drink cans.
对于铝来说，通常不需要特殊的保护，因为它的天然氧化层已经可以防止进一步腐蚀。这就是铝被用于窗框和饮料罐的原因。
Published by TutorHao | Chemistry Revision Series | aleveler.com
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