📚 The Reactions of Metals with Water | 金属与水的反应
Some metals react with cold water to release hydrogen gas and form an alkaline solution called a metal hydroxide. Other metals react only with steam, and some do not react with water at all. Comparing these reactions helps us place metals in the reactivity series and predict how dangerous a reaction might be.
一些金属能与冷水反应，释放出氢气并生成称为金属氢氧化物的碱性溶液。另一些金属只能与水蒸气反应，还有一些金属则完全不与水反应。通过比较这些反应，我们可以把金属放进金属活动性顺序中，并预测某个反应可能有多危险。
1. Why Study Metal-Water Reactions? | 为什么研究金属与水的反应？
Metals react with water at very different speeds. Potassium reacts violently with a lilac flame, sodium fizzes and moves around, calcium bubbles steadily, magnesium is very slow, and copper does not react at all. These differences tell us about the reactivity of each metal.
不同金属与水的反应速度差别很大。钾会伴紫丁香色火焰剧烈反应，钠嘶嘶作响并四处游动，钙会持续冒泡，镁反应非常缓慢，而铜则完全不反应。这些差异告诉我们每种金属的活泼性。
In the laboratory, we never treat all metals in the same way. Reactive metals are stored under oil and handled with forceps, while less reactive metals such as copper can be used for water pipes and kettles.
在实验室中，我们不会用同一种方式处理所有金属。活泼金属保存在油中并用镊子操作，而铜等活泼性较弱的金属可以用于制造水管和水壶。
The reaction with water is therefore not just a set of colourful demonstrations. It is a diagnostic tool: by watching how a metal behaves in water, we can rank it against other metals and predict how it will behave with acids, oxygen and other reactants.
因此，金属与水的反应不只是一组好看的演示实验。它是一种诊断工具：通过观察金属在水中的表现，我们可以把它与其他金属排序，并预测它与酸、氧气及其他反应物会如何反应。
2. The General Word Equation and Products | 一般文字方程式与产物
The general word equation for a reactive metal reacting with cold water is:
活泼金属与冷水反应的一般文字方程式为：
metal + water → metal hydroxide + hydrogen
金属 + 水 → 金属氢氧化物 + 氢气
The metal hydroxide dissolves in water to give an alkaline solution. The pH of this solution is above 7, and it turns red litmus paper blue. Hydrogen gas is given off as bubbles, and if you collect it in a test tube, it burns with a squeaky pop when a lighted splint is placed at the mouth of the tube.
金属氢氧化物溶于水后形成碱性溶液。该溶液的 pH 大于 7，能使红色石蕊试纸变蓝。氢气以气泡形式放出；如果把它收集在试管中，将点燃的木条放在试管口，它会发出尖锐的爆鸣声。
When a metal reacts with steam instead of cold water, the product is usually a metal oxide, not a metal hydroxide. The general word equation is:
当金属与水蒸气而不是冷水反应时，产物通常是金属氧化物，而不是金属氢氧化物。一般文字方程式为：
metal + steam → metal oxide + hydrogen
金属 + 水蒸气 → 金属氧化物 + 氢气
This difference is important in exams. The term "steam" means water in the gas state, and the reaction is carried out by passing steam over heated metal. The hydrogen produced can be collected over water or in a gas syringe.
这一区别在考试中很重要。"水蒸气"指气态水，反应通过让水蒸气通过加热的金属来进行。生成的氢气可以用排水法或气体注射器收集。
3. The Reactivity Series and the Water Test | 金属活动性顺序与水反应检验
The reactivity series lists metals in order of how vigorously they react. The reaction with water is one of the classic tests used to build this series.
金属活动性顺序按金属反应的剧烈程度排列。与水反应是建立该顺序的经典检验之一。
From the most reactive to the least reactive towards water, the order around this topic is: potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, lead, copper, silver, gold.
就与水反应而言，从最活泼到最不活泼的顺序大致为：钾、钠、锂、钙、镁、铝、锌、铁、铅、铜、银、金。
A metal that reacts with cold water must be more reactive than one that needs steam, and a metal that needs steam is more reactive than one that does not react with water at all. This logic allows us to compare metals even when we cannot test all of them directly.
能与冷水反应的金属一定比需要水蒸气才反应的金属更活泼，而需要水蒸气才反应的金属又比完全不与水反应的金属更活泼。即使不能直接测试所有金属，这套逻辑也让我们能够比较它们。
4. Group 1 Metals: Potassium, Sodium and Lithium | 第一族金属：钾、钠和锂
Potassium, sodium and lithium are Group 1 metals. They all react with cold water to form a metal hydroxide and hydrogen, and the reaction becomes more violent as you go down the group: lithium is the calmest, sodium is faster, and potassium is the most violent.
钾、钠和锂都是第一族金属。它们都能与冷水反应，生成金属氢氧化物和氢气；越往下走，反应越剧烈：锂最平静，钠更快，钾最剧烈。
Potassium reacts violently with a lilac flame. It skims across the surface, and the heat produced can ignite the hydrogen gas. Sodium fizzes and moves around on the surface, sometimes with a yellow-orange flame. Lithium fizzes steadily and moves more slowly.
钾会伴紫丁香色火焰剧烈反应，在水面上迅速滑动，产生的热量可点燃氢气。钠嘶嘶作响并在水面上四处游动，有时带有黄橙色火焰。锂稳定地冒泡，移动较慢。
For potassium: 2K + 2H₂O → 2KOH + H₂↑. For sodium: 2Na + 2H₂O → 2NaOH + H₂↑. For lithium: 2Li + 2H₂O → 2LiOH + H₂↑.
钾：2K + 2H₂O → 2KOH + H₂↑。钠：2Na + 2H₂O → 2NaOH + H₂↑。锂：2Li + 2H₂O → 2LiOH + H₂↑。
The hydroxides formed are strong alkalis. Potassium hydroxide, sodium hydroxide and lithium hydroxide all dissolve well in water and give strongly alkaline solutions. If universal indicator is added, the solution turns purple or dark blue.
生成的氢氧化物都是强碱。氢氧化钾、氢氧化钠和氢氧化锂都易溶于水，形成强碱性溶液。如果加入通用指示剂，溶液会变成紫色或深蓝色。
5. Calcium and Magnesium: Steady and Slow Reactions | 钙与镁：稳定与缓慢的反应
Calcium reacts steadily with cold water. It sinks and bubbles of hydrogen are produced, and the water becomes cloudy because calcium hydroxide is only slightly soluble.
钙与冷水稳定反应。它下沉并产生氢气泡，水会变浑浊，因为氢氧化钙仅微溶于水。
Ca + 2H₂O → Ca(OH)₂ + H₂↑ arbon dioxide. When carbon dioxide is bubbled through limewater, the solution turns milky.
Ca + 2H₂O → Ca(OH)₂ + H₂↑。这种浑浊溶液就是石灰水，可用于检验二氧化碳。当二氧化碳通入石灰水时，溶液会变浑浊。
cts much faster with hot water, and with steam the reaction is clear: Mg + H₂O → MgO + H₂.
镁与冷水反应极其缓慢。它与热水反应快得多，而与水蒸气反应则很明显：Mg + H₂O → MgO + H₂。
This is why magnesium is not described as reacting with cold water in the same way as sodium or calcium. In the reactivity series it sits below calcium but above zinc and iron. Magnesium ribbon must be cleaned before use because a layer of magnesium oxide slows the reaction.
因此，镁不能像钠或钙那样被描述为与冷水反应。在金属活动性顺序中，它位于钙之下、锌和铁之上。镁条使用前必须打磨，因为表面的氧化镁层会减慢反应。
6. Metals That Need Steam: Zinc, Iron and Aluminium | 需要水蒸气的金属：锌、铁和铝
Zinc, iron and aluminium do not react with cold water, but they do react with steam when heated strongly. The products are a metal oxide and hydrogen gas.
锌、铁和铝不与冷水反应，但在强热下能与水蒸气反应，产物是金属氧化物和氢气。
Zinc: Zn + H₂O → ZnO + H₂. Iron: 3Fe + 4H₂O → Fe₃O₄ + 4H₂. Al
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图