KS3 Chemistry Unit 7 Review | KS3 化学第7单元复习

📚 KS3 Chemistry Unit 7 Review | KS3 化学第7单元复习

This review guide brings together the key ideas from KS3 chemistry unit 7, including particles, atoms, reactions, acids and alkalis, separation techniques, and the periodic table. Use it to check your understanding and spot any gaps before an end-of-topic test.

本复习指南汇总了 KS3 化学第 7 单元的核心内容，包括粒子、原子、化学反应、酸与碱、分离技术以及元素周期表。利用它来检查你的理解，并在单元测试前找出知识漏洞。

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1. Particle Model and States of Matter | 粒子模型与物质状态

All matter is made of tiny particles that are constantly moving. The arrangement and movement of these particles explain the properties of solids, liquids and gases.

所有物质都由不断运动的微小粒子组成。粒子的排列方式和运动状态可以解释固体、液体和气体的性质。

In solids, particles are packed closely in a regular pattern and only vibrate in fixed positions. In liquids, particles are close but can slide past each other. In gases, particles are far apart and move quickly in all directions.

在固体中，粒子紧密排列成规则结构，只能在固定位置振动。在液体中，粒子彼此靠近但可以相互滑动。在气体中，粒子相距很远，朝各个方向快速运动。

Changes of state, such as melting, freezing, boiling and condensing, are physical changes. The particles themselves do not change; only their arrangement and energy change.

熔化、凝固、沸腾和凝结等状态变化属于物理变化。粒子本身没有改变，改变的只是它们的排列方式和能量。

Diffusion is faster in gases than in liquids because gas particles have more energy and move more quickly. Heating a substance gives particles more kinetic energy, which can cause expansion.

气体中的扩散比液体中快，因为气体粒子能量更高、运动更快。加热物质会使粒子获得更多动能，从而导致膨胀。

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2. Atoms, Elements and Compounds | 原子、元素与化合物

An element is a substance made of only one type of atom. Elements cannot be broken down into simpler substances by chemical reactions.

元素是由同一种原子组成的物质。元素不能通过化学反应分解成更简单的物质。

A compound contains two or more different elements chemically joined together. The properties of a compound are usually very different from the elements that make it.

化合物含有两种或多种不同元素，它们通过化学方式结合在一起。化合物的性质通常与组成它的元素非常不同。

For example, sodium is a reactive metal and chlorine is a toxic green gas, but sodium chloride is the white solid we use as table salt. This shows that chemical bonding creates new substances.

例如，钠是一种活泼金属，氯是一种有毒的绿色气体，但氯化钠却是我们用作食盐的白色固体。这说明化学键合会生成新物质。

Chemical symbols show elements: O for oxygen, Fe for iron, and Na for sodium. Chemical formulae show the number of each atom in a compound, such as H₂O for water and CO₂ for carbon dioxide.

化学符号表示元素：O 代表氧，Fe 代表铁，Na 代表钠。化学式表示化合物中各种原子的数量，例如 H₂O 表示水，CO₂ 表示二氧化碳。

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3. The Periodic Table | 元素周期表

The periodic table arranges all known elements in order of atomic number. Elements with similar properties are placed in the same vertical columns called groups.

元素周期表按原子序数排列所有已知元素。性质相似的元素被放在同一纵列中，称为族。

Group 1 elements are the alkali metals. They are soft, shiny when cut, and react vigorously with water. Reactivity increases as you go down the group.

第 1 族元素是碱金属。它们质地柔软，切开后有光泽，并与水剧烈反应。越往下，反应性越强。

Group 7 elements are the halogens. They are non-metals and exist as diatomic molecules such as F₂, Cl₂, Br₂ and I₂. Reactivity decreases as you go down the group.

第 7 族元素是卤素。它们是非金属，以双原子分子形式存在，如 F₂、Cl₂、Br₂ 和 I₂。越往下，反应性越弱。

Group 0 elements are the noble gases. They are very unreactive because their outer shells are full. Helium, neon and argon are examples.

第 0 族元素是稀有气体。它们非常不活泼，因为外层电子已满。例如氦、氖和氩。

Metals are found on the left and centre of the periodic table, while non-metals are found on the right. The zig-zag line separates metals from non-metals.

金属位于周期表的左侧和中部，非金属位于右侧。锯齿形分界线把金属和非金属分开。

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4. Chemical Reactions and Word Equations | 化学反应与文字方程式

A chemical reaction is a change in which new substances are made. Signs of a reaction include colour change, gas bubbles, temperature change, or a precipitate forming.

化学反应是生成新物质的变化。反应的迹象包括颜色变化、产生气泡、温度变化或生成沉淀。

In a chemical reaction, reactants are used up and products are formed. The total mass stays the same because atoms are not created or destroyed; they are only rearranged.

在化学反应中，反应物被消耗，生成物形成。总质量保持不变，因为原子既不会凭空产生也不会消失，只是重新排列。

A word equation shows the reactants and products in words. For example: magnesium + oxygen → magnesium oxide.

文字方程式用文字表示反应物和生成物。例如：镁 + 氧气 → 氧化镁。

methane + oxygen → carbon dioxide + water

This word equation summarises the combustion of methane. The arrow means ‘reacts to produce’.

这个文字方程式概括了甲烷的燃烧。箭头表示 “反应生成”。

Reactions can be exothermic, releasing heat energy, or endothermic, absorbing heat energy. Combustion and neutralisation are usually exothermic.

反应可以是放热的，释放热能；也可以是吸热的，吸收热能。燃烧和中和反应通常是放热的。

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5. Acids and Alkalis | 酸与碱

Acids have a pH less than 7. Common examples include hydrochloric acid, sulfuric acid and citric acid. Alkalis have a pH greater than 7; sodium hydroxide is a common alkali.

酸的 pH 值小于 7。常见例子包括盐酸、硫酸和柠檬酸。碱的 pH 值大于 7；氢氧化钠是一种常见碱。

A neutral solution has a pH of exactly 7. Pure water is neutral. Indicators change colour in acids and alkalis; litmus turns red in acid and blue in alkali.

中性溶液的 pH 值恰好为 7。纯水是中性的。指示剂在酸和碱中会变色；石蕊在酸中变红，在碱中变蓝。

Universal indicator gives a range of colours from red for strong acids through green for neutral to purple for strong alkalis. It is more useful than litmus because it shows how acidic or alkaline a solution is.

通用指示剂显示从强酸的红色、中性的绿色

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