Making a Compound | 制备化合物

📚 Making a Compound | 制备化合物

In KS3 chemistry, making a compound is a core practical idea that links elements, reactions and chemical formulae. A compound is produced when two or more different elements take part in a chemical reaction and their atoms become chemically bonded. This unit explains how compounds are made, how to represent the reactions, and how to tell a compound from a mixture.

在 KS3 化学中，制备化合物是连接元素、反应和化学式的核心实践概念。当两种或多种不同元素参与化学反应，原子通过化学键结合时，就生成了化合物。本单元解释化合物是如何制备的、如何表示这些反应，以及如何区分化合物和混合物。

1. Elements and Compounds: The Starting Point | 元素与化合物：起点

An element is a pure substance made of only one type of atom. Magnesium, iron, sulfur, oxygen and hydrogen are all elements. Each element has its own chemical symbol, such as Mg for magnesium and Fe for iron.

元素是由同一种原子组成的纯净物。镁、铁、硫、氧和氢都是元素。每种元素都有自己的化学符号，例如镁用 Mg 表示，铁用 Fe 表示。

A compound is a pure substance made of two or more different elements that are chemically joined. The properties of a compound are usually very different from the properties of the elements that made it. For example, sodium is a reactive metal and chlorine is a toxic gas, but the compound sodium chloride is common table salt.

化合物是由两种或多种不同元素通过化学键结合而成的纯净物。化合物的性质通常与组成它的元素性质截然不同。例如，钠是一种活泼金属，氯是一种有毒气体，但化合物氯化钠就是普通的食盐。

Common compounds you meet at KS3 include water H₂O, carbon dioxide CO₂, magnesium oxide MgO and iron sulfide FeS. Each has a fixed composition that is always the same.

你在 KS3 阶段会遇到的常见化合物包括水 H₂O、二氧化碳 CO₂、氧化镁 MgO 和硫化铁 FeS。每种化合物都有固定且始终不变的组成。

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2. What Happens When a Compound Is Made? | 制备化合物时发生了什么？

Making a compound is a chemical change, not a physical change. The atoms of the starting elements are rearranged, and new chemical bonds form between them. This is completely different from simply mixing two substances together.

制备化合物是一种化学变化，而不是物理变化。起始元素的原子重新排列，并在它们之间形成新的化学键。这与简单地把两种物质混合在一起完全不同。

During a chemical reaction, bonds between atoms in the reactants break, and new bonds form to make the products. Energy is usually transferred to the surroundings as heat or light. Reactions that give out heat are called exothermic reactions.

在化学反应中，反应物中原子之间的键断裂，形成新键生成产物。能量通常以热或光的形式传递给周围环境。放出热量的反应称为放热反应。

For example, burning magnesium in air transfers so much energy as heat and light that a bright white flame appears. New chemical bonds form between magnesium and oxygen atoms to make magnesium oxide.

例如，镁在空气中燃烧时会以热和光的形式传递大量能量，因此产生明亮的白色火焰。镁原子和氧原子之间形成新的化学键，生成氧化镁。

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3. Signs That a Compound Has Formed | 化合物形成的迹象

You can often tell a compound has been made by observing changes during the reaction. Useful signs include a colour change, a temperature change, light being given off, a new solid appearing, or bubbles of gas being produced.

通过观察反应过程中的变化，通常可以判断已经生成了化合物。有用的迹象包括颜色变化、温度变化、发光、出现新固体或产生气泡。

When grey iron powder and yellow sulfur powder are heated together, the mixture glows red and a dark grey solid called iron sulfide forms. The product looks completely different from the starting elements.

当灰色铁粉和黄色硫粉一起加热时，混合物发出红光，生成一种叫做硫化铁的深灰色固体。产物看起来与起始元素完全不同。

A compound cannot be separated into its elements by physical methods such as using a magnet, filtering or dissolving. Chemical reactions are needed to break the bonds in a compound.

化合物不能通过磁铁、过滤或溶解等物理方法分离成各元素。要破坏化合物中的化学键，必须通过化学反应。

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4. Writing Word Equations | 书写文字表达式

A word equation shows the names of the reactants and products in a chemical reaction. The reactants are written on the left and the products on the right. An arrow means ‘reacts to form’, while the plus sign means ‘reacts with’.

文字表达式显示化学反应中反应物和产物的名称。反应物写在左边，产物写在右边。箭头表示“反应生成”，加号表示“与……反应”。

For making magnesium oxide, the word equation is: magnesium + oxygen → magnesium oxide

制备氧化镁的文字表达式为：镁 + 氧气 → 氧化镁

For making iron sulfide, the word equation is: iron + sulfur → iron sulfide

制备硫化铁的文字表达式为：铁 + 硫 → 硫化铁

Word equations are very useful for describing reactions, but they do not show how many atoms are involved or the chemical formulae of the substances.

文字表达式对于描述化学反应非常有用，但它们不显示涉及多少原子，也不显示物质的化学式。

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5. Writing Balanced Symbol Equations | 书写配平的符号方程式

A symbol equation uses chemical symbols and formulae to show a reaction. It gives more information than a word equation because it shows the number of atoms involved.

符号方程式使用化学符号和化学式来表示反应。它比文字表达式提供更多信息，因为能显示参与反应的原子数量。

When magnesium burns in oxygen, the balanced symbol equation is:

镁在氧气中燃烧时，配平的符号方程式为：

2Mg + O₂ → 2MgO

This equation shows that two magnesium atoms react with one oxygen molecule to form two units of magnesium oxide. The equation is balanced because the same number of each type of atom appears on both sides.

该方程式表示两个镁原子与一个氧分子反应，生成两个氧化镁单元。该方程式是配平的，因为两侧每种原子的数量相同。

Other simple balanced equations you should know include: Fe + S → FeS and 2H₂ + O₂ → 2H₂O.

你应该掌握的其他简单配平方程式包括：Fe + S → FeS 和 2H₂ + O₂ → 2H₂O。

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6. Making Magnesium Oxide | 制备氧化镁

Magnesium oxide is made by burning magnesium ribbon in air. Hold the ribbon with tongs and place it in a Bunsen burner flame. The magnesium burns with a brilliant white light, and a white ash is produced.

氧化镁是通过在空气中燃烧镁条制备的。用坩埚钳夹住镁条，将其放在本生灯火焰中。镁燃烧时发出耀眼的白色光，并产生白色灰烬。

The word equation is: magnesium + oxygen → magnesium oxide

文字表达式为：镁 + 氧气 → 氧化镁

The symbol equation is: 2Mg + O₂ → 2MgO

符号方程式为：2Mg + O₂ → 2MgO

The white ash is magnesium oxide, an ionic compound made of magnesium ions Mg²⁺ and oxide ions O²⁻. These ions are held together by strong electrostatic forces called ionic bonds.

白色灰烬是氧化镁，一种由镁离子 Mg²⁺ 和氧离子 O²⁻ 组成的离子化合物。这些离子通过称为离子键的强大静电引力结合在一起。

Do not look directly at the burning magnesium because the intense light can damage your eyes. Wear safety goggles and use heat-proof equipment.

不要直视燃烧的镁，因为强光会损伤眼睛。务必佩戴护目镜并使用耐热器材。

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7. Making Iron Sulfide | 制备硫化铁

Iron sulfide is a classic KS3 compound made in the laboratory. Mix iron filings and yellow sulfur powder, then place the mixture in a test tube. Heat the test tube strongly using a Bunsen burner.

硫化铁是 KS3 实验室中制备的经典化合物。将铁屑和黄色硫粉混合，然后把混合物放入试管中。用本生灯强热试管。

At first the mixture is grey and yellow. After heating, the mixture glows red and a dark

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