📚 Year 7 CCEA Chemistry: Core Knowledge Review | CCEA 7年级化学：核心知识点梳理
Welcome to your Year 7 Chemistry journey! This article brings together the essential ideas you will meet in the CCEA Key Stage 3 curriculum. From the tiniest particles to the reactions that change substances, these core topics will give you a strong foundation for all your future chemistry learning.
欢迎开启七年级化学的学习之旅！本文梳理了 CCEA 关键阶段 3 课程中的核心概念。从最微小的粒子到改变物质的反应，这些基础主题将为你未来的化学学习打下坚实的基础。
1. What is Chemistry? | 什么是化学？
Chemistry is the study of matter, its properties, and how substances change and interact with each other. It helps us understand everything from why food cooks to how medicines work.
化学是研究物质及其性质，以及物质如何变化和相互作用的科学。它帮助我们理解从食物烹饪到药物作用的一切现象。
In Year 7, you start by looking at the materials around you, asking questions about what they are made of, and carrying out simple investigations to find answers.
在七年级，你将从观察身边的材料开始，提出问题——它们是由什么组成的，并通过简单的实验探究来寻找答案。
2. States of Matter | 物质的状态
Everything around us exists as either a solid, a liquid, or a gas. These are the three common states of matter, and each behaves in a distinct way.
我们周围的一切物质都以固态、液态或气态存在。这是物质的三种常见状态，每种状态都有独特的表现方式。
Solids have a fixed shape and a fixed volume. The particles are packed tightly together, usually in a regular pattern, and can only vibrate in place. Liquids have a fixed volume but take the shape of their container. The particles are close together but can move past each other. Gases have no fixed shape or volume; they spread out to fill any container. Their particles are far apart and move rapidly in all directions.
固体具有固定的形状和固定的体积，粒子紧密堆积，通常呈规则排列，只能在原地振动。液体有固定体积，但形状随容器而变，粒子紧密但可以相互滑动。气体没有固定的形状和体积，会扩散充满整个容器，粒子相距很远并快速向各个方向运动。
3. Changes of State | 状态变化
Substances can change from one state to another when they are heated or cooled. These physical changes are reversible and do not produce new substances.
物质在加热或冷却时可以从一种状态变为另一种状态。这些物理变化是可逆的，不会产生新物质。
Key changes of state include: melting (solid to liquid), freezing (liquid to solid), boiling or evaporation (liquid to gas), and condensation (gas to liquid). Sometimes a solid can turn directly into a gas through sublimation, and the reverse is called deposition.
关键的状态变化包括：熔化（固体→液体）、凝固（液体→固体）、沸腾或蒸发（液体→气体）、冷凝（气体→液体）。有时固体能直接变为气体，这叫做升华，而其逆过程称为凝华。
During a change of state, the temperature stays constant while the particles gain or lose energy to overcome forces holding them together.
在状态变化过程中，温度保持不变，而粒子获得或失去能量以克服将它们束缚在一起的力。
4. Particles in Matter | 物质中的粒子
All matter is made of tiny particles that are too small to see. These particles are atoms, molecules, or ions, and they are constantly moving. The particle model helps explain the properties of solids, liquids, and gases.
所有物质都由微小的粒子组成，这些粒子小到看不见。它们可能是原子、分子或离子，并且不停地运动。粒子模型有助于解释固体、液体和气体的性质。
In solids, strong forces hold the particles close, so they only vibrate. In liquids, the forces are weaker, allowing particles to slide around. In gases, the forces are negligible, so particles move freely.
在固体中，强大的作用力将粒子紧紧束缚在一起，因此粒子只能振动。在液体中，作用力较弱，粒子可以滑动。在气体中，作用力可忽略不计，粒子可以自由运动。
This model also explains diffusion: the spreading out of particles from an area of high concentration to an area of low concentration. You can observe diffusion when a smell spreads across a room or food colouring mixes in water.
这个模型还可以解释扩散现象：粒子从高浓度区域向低浓度区域扩散。你可以通过气味在房间中传播或食用色素在水中扩散的现象来观察扩散。
5. Elements, Compounds and Mixtures | 元素、化合物与混合物
Substances can be classified as elements, compounds, or mixtures. An element is a pure substance made of only one type of atom. Examples include oxygen (O₂), iron (Fe), and gold (Au).
物质可分为元素、化合物或混合物。元素是由同一种原子组成的纯净物，例如氧气 (O₂)、铁 (Fe) 和金 (Au)。
A compound is a pure substance made of two or more different types of atoms chemically bonded together. Water (H₂O) and carbon dioxide (CO₂) are compounds. The properties of a compound are usually very different from the elements that make it.
化合物是由两种或多种不同原子通过化学键结合而成的纯净物。水 (H₂O) 和二氧化碳 (CO₂) 都是化合物。化合物的性质通常与其组成元素的性质截然不同。
A mixture contains two or more different substances that are not chemically joined. Air is a mixture of gases; salty water is a mixture of salt and water. Mixtures can often be separated by physical methods.
混合物包含两种或多种没有通过化学键结合的物质。空气是气体混合物；盐水是盐和水的混合物。混合物通常可以通过物理方法分离。
6. The Atom | 原子
The atom is the smallest particle of an element that still has the properties of that element. Atoms are incredibly small – about 0.00000001 cm across.
原子是元素中仍具有该元素性质的最小粒子。原子极其微小——直径大约只有 0.00000001 厘米。
An atom consists of a tiny, dense nucleus made of protons and neutrons, surrounded by electrons moving in layers called shells. Protons have a positive charge (+1), electrons have a negative charge (−1), and neutrons are neutral.
原子由一个微小致密的原子核组成，核内包含质子和中子，核外电子在称为电子层的轨道上运动。质子带一个单位正电荷 (+1)，电子带一个单位负电荷 (−1)，中子不带电。
In a neutral atom, the number of protons equals the number of electrons. The number of protons, called the atomic number, determines which element the atom is. For example, every carbon atom has 6 protons.
在中性原子中，质子数等于电子数。质子的数目称为原子序数，它决定了原子属于哪种元素。例如，每个碳原子都有 6 个质子。
7. The Periodic Table | 元素周期表
The periodic table is a chart that organises all known elements in order of increasing atomic number. Elements are arranged into rows (periods) and columns (groups) based on their properties.
元素周期表是一张按原子序数递增顺序排列所有已知元素的图表。元素根据其性质排列成行（周期）和列（族）。
Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell. For instance, Group 1 metals (like sodium and potassium) are all very reactive and soft. Group 0, the noble gases, are unreactive because they have a full outer shell.
同一族的元素具有相似的化学性质，因为它们的最外层电子数相同。例如，第 1 族金属（如钠和钾）都非常活泼且质地柔软。第 0 族是稀有气体，它们因为最外层已满而极不活泼。
On the periodic table, you can find metals on the left and centre, and non-metals on the right. A zigzag line often separates them, though some elements near it are called metalloids.
在周期表中，金属位于左侧和中部，非金属位于右侧。通常有一条锯齿形界线将它们分开，不过靠近界线的某些元素被称为类金属。
8. Chemical Reactions | 化学反应
A chemical reaction occurs when substances (reactants) are transformed into new substances (products). During a reaction, atoms are rearranged, but no atoms are created or destroyed.
当物质（反应物）转变为新的物质（产物）时，就发生了化学反应。在反应过程中，原子重新排列，但原子不会被创造或毁灭。
pitate) forming. Reactions can be written using word equations, such as: methane + oxygen → carbon dioxide + water.
你可以通过一些迹象来识别化学反应，例如颜色变化、温度变化、产生气泡，或者形成新的固体（沉淀）。反应可以用文字方程式来表示，例如：甲烷 + 氧气 → 二氧化碳 + 水。
Some reactions, like burning fuel, release energy as heat and light, while others, like photosynthesis, absorb energy. Understanding conservation of mass – that the total mass of reactants equals the total mass of products – is a key idea.
有些反应（如燃料燃烧）以热和光的形式释放能量，而另一些反应（如光合作用）则吸收能量。理解质量守恒定律——反应物的总质量等于产物的总质量——是一个核心概念。
9. Acids and Alkalis | 酸和碱
Acids and alkalis are two important groups of chemicals. Acids are substances that release hydrogen ions (H⁺) when dissolved in water. Common acids include lemon juice (citric acid), vinegar (acetic acid), and laboratory acids like hydrochloric acid.
酸和碱是两类重要的化学物质。酸是溶于水时会释放氢离子 (H⁺) 的物质。常见酸包括柠檬汁（柠檬酸）、醋（乙酸），以及实验室的盐酸等。
Alkalis are soluble bases that release hydroxide ions (OH⁻) in water. Examples include sodium hydroxide and soap solutions. The strength of an acid or alkali is measured on the pH scale, which runs from 0 (very acidic) to 14 (very alkaline), with 7 being neutral.
碱是可溶性的碱，溶于水时释放氢氧根离子 (OH⁻)。例子包括氢氧化钠和肥皂溶液。酸或碱的强度用 pH 值来衡量，范围从 0（极强酸性）到 14（极强碱性），7 为中性。
Indicators, such as litmus paper, change colour to show whether a solution is acidic, alkaline, or neutral. Blue litmus turns red in acid; red litmus turns blue in alkali.
指示剂（如石蕊试纸）会变色以显示溶液是酸性、碱性还是中性。蓝色石蕊在酸中变红；红色石蕊在碱中变蓝。
When an acid reacts with an alkali, a neutralisation reaction occurs, producing a salt and water. This type of reaction is very important in everyday life, from treating indigestion to cleaning up spills.
当酸与碱反应时，发生中和反应，生成盐和水。这类反应在日常生活中非常重要，从治疗消化不良到清理溢出物都有应用。
10. Separation Techniques | 分离技术
Mixtures can be separated using physical methods that take advantage of differences in properties such as particle size, boiling point, or solubility.
混合物可以利用物质在颗粒大小、沸点或溶解度等性质上的差异，通过物理方法进行分离。
Filtration separates an insoluble solid from a liquid. The mixture is poured through filter paper; the solid stays behind while the liquid passes through. Evaporation removes a solvent by heating, leaving the dissolved solid behind. Distillation separates a liquid from a solution by boiling the liquid and then condensing the vapour back into a pure liquid. Chromatography separates dissolved substances based on how they travel through a material such as paper.
过滤用于将不溶性固体与液体分离。混合物通过滤纸倒入，固体留在滤纸上，液体则穿过。蒸发通过加热除去溶剂，留下溶解的固体。蒸馏通过将液体煮沸，再将蒸气冷凝回纯净液体的方法，将液体从溶液中分离出来。色谱法根据物质在纸张等材料中迁移速度的不同来分离溶解的物质。
These techniques are used in real life: filtration for water treatment, distillation for making pure alcohol, and chromatography for testing food dyes.
这些技术在现实生活中都有应用：过滤用于水处理，蒸馏用于制造纯酒精，色谱法用于检测食用色素。
11. Physical and Chemical Changes | 物理变化与化学变化
Changes that happen to materials can be classified as physical or chemical. A physical change alters the form or state of a substance but does not change what it is made of. Melting ice and dissolving sugar in water are physical changes because no new substance is formed.
物质发生的变化可分为物理变化和化学变化。物理变化改变物质的形式或状态，但不改变其组成。冰融化、糖溶于水都是物理变化，因为没有新物质生成。
A chemical change, however, produces one or more new materials. Signs of a chemical change include bubbling, colour change, temperature change, or the formation of a precipitate. Baking a cake and frying an egg are everyday examples of chemical reactions.
而化学变化会生成一种或多种新物质。化学变化的迹象包括冒泡、颜色改变、温度变化或生成沉淀。烘烤蛋糕和煎鸡蛋就是日常生活中的化学变化实例。
It is important to remember that physical changes are usually easier to reverse than chemical changes. When you freeze water, you get ice; when you melt ice, you get water back. But you cannot 'unbake' a cake.
重要的是一点：物理变化通常比化学变化更容易逆转。水结冰得到冰，冰融化又变回水；但你无法把烘好的蛋糕变回原料。
12. Safety in the Laboratory | 实验室安全
Working safely is the first rule of chemistry. In Year 7, you will learn how to handle apparatus, chemicals, and heat sources responsibly.
安全操作是化学的第一条规则。在七年级，你将学会如何负责任地处理仪器、化学品和热源。
Always wear safety goggles to protect your eyes. Tie back long hair and tuck away loose clothing. Never eat or drink in the lab, and wash your hands after practical work. When heating substances, point test tubes away from yourself and others. Know the hazard symbols: flammable (flame), corrosive (damaging to skin and metals), and toxic (skull and crossbones).
始终佩戴护目镜以保护眼睛。扎好长发，束紧宽松衣物。无做到不在实验室进食或饮水，实验完毕要洗手。加热物质时，试管口要远离自己和他人。务必认识危险符号：可燃（火焰）、腐蚀性（对皮肤和金属造成损害）和有毒（骷髅头）。
If you spill a chemical or break glassware, tell your teacher immediately. Following these simple rules helps everyone enjoy chemistry safely.
如果打翻化学试剂或打破玻璃器皿，立即告诉老师。遵守这些简单的规则，每个人都能安全地享受化学学习的乐趣。
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