📚 Year 7 OCR Chemistry: Core Knowledge Points Review | Year 7 OCR 化学：核心知识点梳理
Welcome to your Year 7 Chemistry revision guide for the OCR curriculum. This article covers all the core knowledge points you need to master, from the particle model and states of matter to atoms, elements, mixtures, chemical changes and the fascinating world of acids and alkalis. Each section is designed to give you clear, concise explanations with real examples to help you understand and remember the key concepts.
欢迎来到针对 OCR 课程的 Year 7 化学复习指南。本文涵盖你需要掌握的所有核心知识点，从粒子模型与物质状态到原子、元素、混合物、化学变化以及迷人的酸碱世界。每个部分都提供清晰、简明的解释和真实例子，帮助你理解和记忆关键概念。
1. The Particle Model | 粒子模型
All matter is made of tiny particles that are far too small to be seen, even with a microscope. These particles are constantly in random motion, and the energy they possess determines how fast they move. There are empty spaces between the particles, with the amount of space depending on the state of the substance.
所有物质都由微小粒子组成，这些粒子小到即使用显微镜也无法看见。粒子处于不断的随机运动中，它们具有的能量决定其运动速度。粒子之间存在空隙，空隙的大小取决于物质的状态。
The particle model explains why solids keep their shape, liquids can flow and gases expand to fill a container. It also helps us understand processes like diffusion, where particles spread from an area of high concentration to an area of low concentration. Diffusion happens fastest in gases because the particles are very energetic and far apart.
粒子模型解释了为什么固体保持形状、液体可以流动而气体会膨胀充满容器。它还帮助我们理解扩散等过程——粒子从高浓度区域向低浓度区域扩散。扩散在气体中最快，因为气体粒子能量高且相距很远。
When particles are heated they gain kinetic energy, moving more vigorously. This can eventually overcome the attractive forces holding them together, leading to a change of state.
粒子受热时会获得动能，运动更加剧烈，最终可能克服将它们束缚在一起的吸引力，从而导致状态变化。
2. States of Matter | 物质状态
There are three common states of matter: solid, liquid and gas. In a solid, particles are packed tightly in a regular pattern; they vibrate on the spot but cannot move freely. This gives solids a fixed shape and volume.
物质有三种常见状态：固态、液态和气态。在固体中，粒子紧密排列成规则的结构；它们只能在原地振动而不能自由移动，因此固体有固定的形状和体积。
In a liquid, the particles are still close together but can slide past each other. A liquid has a fixed volume but takes the shape of its container. In a gas, the particles are far apart and zoom around rapidly in all directions. Gases have no fixed shape or volume and are easily compressed.
在液体中，粒子仍然紧靠在一起，但可以相互滑过。液体有固定的体积，但形状随容器而变。在气体中，粒子相距很远，向各个方向快速移动。气体没有固定的形状或体积，并且容易被压缩。
s gas → liquid. Sublimation (solid → gas) and deposition (gas → solid) also occur in some substances, like solid carbon dioxide (dry ice).
状态变化是物理变化。熔化是固态 → 液态，凝固是液态 → 固态，蒸发和沸腾是液态 → 气态，冷凝是气态 → 液态。升华（固态 → 气态）和凝华（气态 → 固态）也会在某些物质中发生，例如固态二氧化碳（干冰）。
The temperature at which a solid melts is its melting point; the temperature at which a liquid boils is its boiling point. Pure substances have sharp melting and boiling points, while mixtures melt or boil over a range of temperatures.
固体熔化的温度称为熔点；液体沸腾的温度称为沸点。纯净物有固定的熔点和沸点，而混合物在一个温度范围内熔化或沸腾。
3. Atoms, Elements and the Periodic Table | 原子、元素与周期表
An atom is the smallest particle of an element that can exist. Everything around you is made up of atoms. An element is a pure substance that contains only one type of atom. Examples include oxygen (O), hydrogen (H) and iron (Fe).
原子是元素能够存在的最小粒子。你周围的一切都由原子构成。元素是只含有一种原子的纯净物。例如氧（O）、氢（H）和铁（Fe）。
About 118 elements are known, and they are organised in the periodic table. Each element has its own unique chemical symbol, often taken from its English or Latin name. The periodic table groups elements with similar properties together in vertical columns called groups. Horizontal rows are called periods.
已知约有 118 种元素，它们被排列在周期表中。每种元素都有自己独特的化学符号，通常取自其英文或拉丁名称。周期表将性质相似的元素排列在垂直的列中，称为族；水平的
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