📚 Year 8 Edexcel Chemistry: Core Knowledge Review | Year 8 Edexcel 化学：核心知识点梳理
Welcome to your Year 8 Edexcel Chemistry revision guide. This article reviews the essential topics you have studied this year, from the particle model to acids and reactions. Use the paired English and Chinese explanations to strengthen both your subject knowledge and your scientific vocabulary.
欢迎来到 Year 8 Edexcel 化学复习指南。本文将梳理你今年学习的所有核心主题，从粒子模型到酸碱和化学反应。双语配对讲解，帮助你在巩固科学知识的同时提升学科英语能力。
1. States of Matter and the Particle Model | 物质的状态与粒子模型
All matter is made of tiny particles. The properties of solids, liquids and gases can be explained by how these particles are arranged and how they move. This idea is called the particle model.
所有物质都由微小粒子构成。固态、液态和气态的性质可以通过粒子的排列方式和运动方式来解释。这个理论称为粒子模型。
In a solid, particles are closely packed in a fixed, regular arrangement. They can only vibrate in place, which is why solids have a definite shape and volume.
固态中，粒子紧密排列，位置固定且有规律。它们只能在原地振动，因此固体具有固定的形状和体积。
In a liquid, particles are still close together but can slide past each other. This allows liquids to flow and take the shape of their container, but they keep a constant volume.
液态中，粒子仍然紧挨在一起，但可以相互滑动。因此液体能够流动并随容器形状变化，但体积保持不变。
In a gas, particles are far apart and move rapidly in all directions. Gases have no fixed shape or volume and can be compressed easily.
气态中，粒子相距很远，向四面八方快速运动。气体没有固定的形状和体积，容易被压缩。
Changes of state – such as melting, freezing, boiling and condensing – occur when particles gain or lose energy. These are physical changes, not chemical ones.
状态变化——如熔化、凝固、沸腾和冷凝——发生在粒子获得或失去能量时。这些属于物理变化，而非化学变化。
2. Atoms, Elements and Compounds | 原子、元素和化合物
An atom is the smallest particle of an element that can exist. Every element is made of one type of atom. There are about 100 different elements found naturally.
原子是元素能够存在的最小粒子。每种元素由同一种原子构成。自然界中大约有100种不同的元素。
Elements are listed on the Periodic Table. Each element has its own symbol, such as H for hydrogen, O for oxygen and Fe for iron. The symbol always starts with a capital letter; if there is a second letter, it is lowercase.
元素排列在元素周期表中。每种元素都有各自的符号，例如 H 代表氢，O 代表氧，Fe 代表铁。符号总是以大写字母开头；若有第二个字母，则小写。
When atoms of different elements join together chemically, they form a compound. A compound has different properties from the elements it is made from. For example, water (H₂O) is a compound of hydrogen and oxygen.
不同元素的原子通过化学方式结合在一起时就形成了化合物。化合物的性质与组成它的元素完全不同。例如，水（H₂O）是氢和氧的化合物。
Mixtures are different from compounds because no chemical bonds are formed. In a mixture, the substances are just mixed together and can be separated easily by physical methods.
混合物与化合物不同，因为混合物中没有形成化学键。混合物中的物质只是简单地混合在一起，可以通过物理方法轻松分离。
3. The Periodic Table – A First Look | 元素周期表初探
The Periodic Table arranges all known elements in order of increasing atomic number. It is divided into rows called periods and columns called groups.
元素周期表按原子序数递增的顺序排列所有已知元素。它由称为周期的横行和称为族的竖列组成。
Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell. For example, Group 1 elements are all very reactive metals.
同一族的元素具有相似的化学性质，因为它们最外层电子数相同。例如，第1族元素都是非常活泼的金属。
Metals are found on the left and centre of the table, while non-metals are on the right. There is a zig-zag line that separates metals from non-metals.
金属位于周期表的左侧和中间，非金属位于右侧。表中有一条锯齿状的线将金属和非金属分开。
You need to recognise common elements and their symbols, such as carbon (C), sodium (Na), chlorine (Cl) and calcium (Ca).
你需要认识常见元素及其符号，例如碳 (C)、钠 (Na)、氯 (Cl) 和钙 (Ca)。
4. Chemical Symbols and Formulae | 化学符号与化学式
Chemical symbols represent elements. Chemical formulae show the number and type of atoms in a compound. For instance, CO₂ means one carbon atom and two oxygen atoms.
化学符号代表元素。化学式表示化合物中原子的种类和数目。例如，CO₂ 表示一个碳原子和两个氧原子。
When writing formulae, no number is written if there is only one atom of that element in the compound. The small subscript number shows how many atoms are present.
书写化学式时，如果化合物中某元素只有一个原子，则不写数字。下标小数字表示该原子的个数。
Some common compounds you must know: water (H₂O), carbon dioxide (CO₂), sodium chloride (NaCl), hydrochloric acid (HCl) and sulfuric acid (H₂SO₄).
必须记住的常见化合物有：水 (H₂O)、二氧化碳 (CO₂)、氯化钠 (NaCl)、盐酸 (HCl) 和硫酸 (H₂SO₄)。
Word equations use the names of substances, while balanced symbol equations show the atoms rearranging. In Year 8, you mainly write word equations.
文字方程式使用物质名称，而配平的符号方程式则显示原子的重新排列。在 Year 8，你主要书写文字方程式。
5. Writing Word Equations | 书写文字方程式
A word equation describes a chemical reaction using the names of reactants and products, with an arrow (→) to show the direction of the change.
文字方程式用反应物和生成物的名称来描述化学反应，并用箭头（→）表示变化的方向。
magnesium + oxygen → magnesium oxide
镁 + 氧气 → 氧化镁
The reactants are written on the left of the arrow, and the products on the right. If there are two or more reactants, they are linked by a plus sign (+). The same rule applies to products.
反应物写在箭头左边，生成物写在右边。如果有两种或更多反应物，用加号 (+) 连接。生成物也一样。
Common word equations
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