📚 Explaining Differences Between Metals and Non-Metals | 解释金属与非金属的差异
In Key Stage 3 Chemistry, one of the first big ideas is that all substances can be divided into metals and non-metals. These two groups behave very differently, both in the way they look and feel and in the way they take part in chemical reactions. Understanding these differences helps us explain why copper is used for electrical wires, why oxygen is a gas at room temperature, and why iron rusts but sulfur burns.
在KS3化学中，最初的重要概念之一是所有物质可以分为金属和非金属。这两类物质在外观、触感以及参与化学反应的方式上都有很大不同。理解这些差异能帮助我们解释为什么铜用作电线、为什么氧气在室温下是气体，以及为什么铁会生锈而硫会燃烧。
1. What Are Metals and Non-Metals? | 什么是金属和非金属？
Metals are elements that are usually shiny, good conductors of heat and electricity, and can be shaped by hammering or pulling. Common examples include iron, copper, aluminium and gold. Non-metals are elements that generally lack these properties; they are often dull, poor conductors, and brittle when solid. Examples include oxygen, carbon, sulfur and chlorine.
金属是通常有光泽、善于导热和导电，并且可以通过锤打或拉伸成形的元素。常见例子包括铁、铜、铝和金。非金属通常缺乏这些性质；它们往往暗淡无光、导热导电性差，固态时易碎。例子包括氧、碳、硫和氯。
- Common metals: iron, copper, aluminium, gold, zinc
- 常见金属：铁、铜、铝、金、锌
- Common non-metals: oxygen, carbon, sulfur, chlorine, nitrogen
- 常见非金属：氧、碳、硫、氯、氮
2. Physical Properties: Appearance and State | 物理性质：外观与状态
Most metals are solids at room temperature and have a characteristic shiny surface when freshly cut or polished. They reflect light, which is described as metallic lustre. The only metal that is liquid at room temperature is mercury. Non-metals, on the other hand, can be solid, liquid or gas at room temperature. For example, carbon and sulfur are solids, bromine is a liquid, and oxygen, nitrogen and chlorine are gases. Solid non-metals are often dull and do not reflect light well.
大多数金属在室温下是固体，新切或抛光后表面有特征性的光泽。它们反射光线，这被称为金属光泽。室温下唯一的液态金属是汞。非金属则不同，在室温下可以是固态、液态或气态。例如，碳和硫是固体，溴是液体，而氧、氮和氯是气体。固态非金属通常暗淡无光，不能很好地反射光线。
3. Conductivity of Heat and Electricity | 导热性和导电性
Metals are excellent conductors of heat and electricity because their outer electrons are free to move through the structure. This is why saucepans are often made of metal, and why electrical wires use copper or aluminium. Non-metals, except for graphite (a form of carbon), are poor conductors. They are often called insulators. For example, plastic, sulfur and oxygen do not allow electricity to flow easily. Graphite conducts electricity because each carbon atom has one delocalised electron, but it is an important exception rather than the rule.
金属是热和电的优良导体，因为它们的外层电子可以在结构中自由移动。这就是为什么锅具常用金属制成，电线使用铜或铝。除石墨（碳的一种形式）外，非金属通常是热和电的不良导体。它们常被称为绝缘体。例如，塑料、硫和氧不易让电流通过。石墨能导电是因为每个碳原子有一个离域电子，但它是一个重要例外，而不是常规。
4. Malleability and Ductility | 延展性与延性
Metals are malleable, meaning they can be hammered or rolled into thin sheets without breaking. They are also ductile, meaning they can be drawn into wires. This is because the layers of metal atoms can slide over each other without the metallic bonding being destroyed. Non-metals are usually brittle when solid. If you hit solid sulfur or carbon with a hammer, it is likely to crack or shatter instead of flattening.
金属具有延展性，意味着可以被锤打或轧制成薄片而不会破裂。它们也具有延性，意味着可以被拉成细丝。这是因为金属原子层可以相互滑动而金属键不会被破坏。非金属固态时通常较脆。如果用锤子敲击固态硫或碳，它们很可能开裂或碎裂，而不是变平。
5. Melting and Boiling Points | 熔点与沸点
Metals generally have high melting and boiling points because the attraction between positive metal ions and the sea of delocalised electrons is strong. For example, iron melts at about 1538 °C. Non-metals often have much lower melting and boiling points. Oxygen boils at -183 °C and nitrogen at -196 °C. However, there are exceptions: diamond, a non-metal form of carbon, has an extremely high melting point because of its giant covalent structure.
金属通常具有较高的熔点和沸点，因为金属阳离子与离域电子海之间的吸引力很强。例如，铁的熔点约为 1538°C。非金属的熔点和沸点通常低得多。氧的沸点为 -183°C，氮的沸点为 -196°C。但也有例外：金刚石是碳的一种非金属形式，由于具有巨型共价结构，熔点极高。
6. Density and Strength | 密度与强度
Metals tend to have high density and are often strong, which makes them useful for building structures, vehicles and tools. Most metals feel heavy for their size. Non-metals have a much wider range of density. Some, like sulfur and phosphorus, have relatively low density and are not strong. Gaseous non-metals such as oxygen and nitrogen have very low density compared with metals.
金属往往密度较高且通常坚固，这使它们适用于建筑结构、车辆和工具。大多数金属相对于体积来说感觉较重。非金属的密度范围则大得多。有些非金属如硫和磷密度相对较低且不坚固。氧、氮等气态非金属与金属相比密度非常低。
7. Chemical Properties: Reactions with Oxygen | 化学性质：与氧气的反应
Metals react with oxygen to form metal oxides, which are usually basic. For example, magnesium burns in air to form magnesium oxide. Non-metals also react with oxygen, but they form non-metal oxides, which are usually acidic. For example, carbon burns in a good supply of oxygen to form carbon dioxide. Many non-metal oxides dissolve in water to make acidic solutions.
金属与氧气反应生成金属氧化物，这些氧化物通常呈碱性。例如，镁在空气中燃烧生成氧化镁。非金属也会与氧气反应，但它们生成非金属氧化物，这些氧化物通常呈酸性。例如，碳在充足的氧气中燃烧生成二氧化碳。许多非金属氧化物溶于水形成酸性溶液。
2Mg + O₂ → 2MgO
C + O₂ → CO₂
8. Reactions with Water and Acids | 与水和酸的反应
Many metals react with dilute acids to produce a salt and hydrogen gas. For example, zinc reacts with hydrochloric acid to make zinc chloride and hydrogen. This is a key test for metals. Only a few very reactive metals, such as potassium and sodium, react directly with cold water. Non-metals do not react with dilute acids in the same way, and they do not produce hydrogen gas. Some non-metals react with water or alkalis, but their reactions are very different. For example, chlorine dissolves in water to form an acidic bleach solution.
许多金属与稀酸反应生成盐和氢气。例如，锌与盐酸反应生成氯化锌和氢气。这是检验金属的一个重要方法。只有少数非常活泼的金属，如钾和钠，会直接与冷水反应。非金属不会以同样方式与稀酸反应，也不会产生氢气。一些非金属会与水或碱反应，但反应非常不同。例如，氯溶于水形成酸性漂白溶液。
Zn + 2HCl → ZnCl₂ + H₂
9. Forming Ions: Electron Transfer | 形成离子：电子转移
A key chemical difference is what happens when atoms form ions. Metal atoms tend to lose electrons from their outer shell to form positive ions, or cations. For example, a sodium atom loses one electron to become Na⁺. Non-metal atoms tend to gain electrons to form negative ions, or anions. A chlorine atom gains one electron to become Cl⁻. This difference in electron behaviour explains many of the physical properties and the way metals and non-metals bond with each other.
一个关键的化学差异在于原子形成离子时发生的情况。金属原子倾向于从外层失去电子，形成正离子，即阳离子。例如，钠原子失去一个电子变成 Na⁺。非金属原子倾向于获得电子，形成负离子，即阴离子。氯原子获得一个电子变成 Cl⁻。这种电子行为的差异解释了金属和非金属的许多物理性质，以及它们彼此结合的方式。
Na → Na⁺ + e⁻
Cl + e⁻ → Cl⁻
10. Oxides and pH | 氧化物与pH
When a metal oxide dissolves in water, it usually forms an alkaline solution with a pH greater than 7. For example, calcium oxide reacts with water to form calcium hydroxide, which is alkaline. Non-metal oxides dissolve in water to form acidic solutions with a pH less than 7. Carbon dioxide dissolves in water to form carbonic acid, making rain slightly acidic. This difference is useful for testing whether an element is a metal or non-metal.
金属氧化物溶于水时，通常形成 pH 大于 7 的碱性溶液。例如，氧化钙与水反应生成氢氧化钙，呈碱性。非金属氧化物溶于水则形成 pH 小于 7 的酸性溶液。二氧化碳溶于水生成碳酸，使雨水略带酸性。这种差异可用于检验某种元素是金属还是非金属。
11. The Periodic Table Position | 周期表中的位置
In the periodic table, metals are found on the left-hand side and in the centre, while non-metals are found on the right-hand side. A zig-zag line often separates metals from non-metals. Elements near this line, such as silicon and germanium, are called metalloids or semi-metals because they have properties in between. Most elements are metals. In Groups 1 and 2 all elements are metals, while Group 7 contains non-metals such as fluorine, chlorine, bromine and iodine.
在周期表中，金属位于左侧和中部，非金属位于右侧。通常用一条锯齿形线将金属与非金属分开。靠近这条线的元素，如硅和锗，被称为类金属或半金属，因为它们的性质介于金属和非金属之间。大多数元素是金属。第1族和第2族的元素都是金属，而第7族包含氟、氯、溴和碘等非金属。
12. Using Properties to Classify and Apply | 利用性质进行分类与应用
Scientists and engineers choose materials based on the differences between metals and non-metals. Copper is used for wiring because it is ductile and conducts electricity. Aluminium is used for aircraft bodies because it is strong but low in density. Plastics and ceramics, which are based on non-metals, are used as insulators and heat-resistant covers. Sulfur is used in fertilisers and matches. Knowing whether an element is a metal or non-metal helps chemists predict how it will behave without having to test every property.
科学家和工程师根据金属与非金属的差异来选择材料。铜用于电线，因为它具有延性且导电。铝用于飞机机身，因为它强度高但密度低。塑料和陶瓷以非金属为基础，用作绝缘体和耐热外壳。硫用于化肥和火柴。知道一种元素是金属还是非金属，有助于化学家预测它的行为，而无需测试每一种性质。
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