📚 Year 7 WJEC Chemistry: Core Knowledge Summary | 七年级 WJEC 化学：核心知识点梳理
This article brings together all the essential topics for Year 7 WJEC Chemistry. We explore particle theory, atoms and elements, chemical reactions, acids and alkalis, separation techniques, and more. Use this guide to build a strong foundation for your science studies.
本文梳理了七年级 WJEC 化学的所有核心主题。我们将探讨粒子理论、原子与元素、化学反应、酸与碱、分离技术等内容。借助这份指南，为你的科学学习打下坚实基础。
1. Particles and States of Matter | 粒子与物质状态
All matter is made of tiny particles – atoms, molecules or ions. In solids the particles are held tightly together in a fixed arrangement and can only vibrate. This explains why solids have a definite shape and cannot be compressed easily.
所有物质都由微小的粒子组成——原子、分子或离子。固体中的粒子紧密地固定在规则排列中，只能在原位振动。这解释了为什么固体有固定的形状且难以压缩。
In liquids the particles are still close but can slide past one another, so a liquid takes the shape of its container and can flow. Liquid particles have more energy than solids and move randomly within the liquid.
液体中的粒子仍然彼此靠近，但可以相互滑过，因此液体会随容器改变形状并能流动。液体粒子的能量比固体高，在液体内随机运动。
Gas particles are far apart and move very fast in all directions. Gases have no fixed shape or volume, can be compressed easily, and spread out to fill any container.
气体中的粒子相距很远，并向各个方向快速运动。气体没有固定的形状或体积，容易压缩，并会扩散充满整个容器。
Changes of state – melting, freezing, boiling, condensing and subliming – are physical changes. The particles themselves stay the same; only their arrangement and energy change. Diffusion is evidence for moving particles: perfume smell spreading across a room is an example.
状态变化——熔化、凝固、沸腾、凝结和升华——都是物理变化。粒子本身保持不变，改变的只是它们的排列方式和能量。扩散是粒子运动的证据：比如香水气味在房间中散开。
2. Atoms, Elements and Compounds | 原子、元素与化合物
An atom is the smallest particle of an element that can take part in a chemical reaction. Each element is made up of only one type of atom. There are about 118 known elements, from hydrogen to oganesson, each represented by a chemical symbol, such as H for hydrogen and Fe for iron.
原子是能参与化学反应的元素最小粒子。每种元素仅由一种原子构成。已知元素约有118种，从氢到鿫，每种元素用一个化学符号表示，例如氢为 H，铁为 Fe。
When two or more different atoms join together by chemical bonds, a compound is formed. Water (H₂O), carbon dioxide (CO₂) and sodium chloride (NaCl) are all compounds. The properties of a compound are completely different from the elements it contains.
当两个或多个不同原子通过化学键结合时，就形成了化合物。水（H₂O）、二氧化碳（CO₂）和氯化钠（NaCl）都是化合物。化合物的性质与其组成元素的性质完全不同。
In contrast, a mixture contains two or more substances that are not chemically combined, meaning they can be separated by physical methods. Air, sea water and soil are everyday mixtures.
相对地，混合物含有两种或多种未经过化学结合的物质，因此可以通过物理方法分离。空气、海水和土壤都是常见的混合物。
3. The Periodic Table | 元素周期表
The periodic table arranges all the elements in order of increasing atomic number (the number of protons in the nucleus). The horizontal rows are called periods, and the vertical columns are called groups.
元素周期表按原子序数（原子核内质子数）递增的顺序排列所有元素。横排称为周期，竖列称为族。
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 metals (lithium, sodium, potassium) are all very reactive and soft. Group 7 elements (fluorine, chlorine, bromine) are known as halogens, and Group 0 or 8 elements (helium, neon, argon) are noble gases – very unreactive.
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族金属（锂、钠、钾）都很活泼且质软。第7族元素（氟、氯、溴）被称为卤素，而第0或第8族元素（氦、氖、氩）是稀有气体，极不活泼。
Metals are found on the left and centre of the table, while non‑metals occupy the right‑hand side. The bold zig‑zag line separates them, with elements like silicon and germanium touching the line often described as semi‑metals or metalloids.
金属位于周期表左侧及中部，非金属位于右侧。一条粗锯齿线将它们分开，靠近这条线的硅、锗等元素通常被称为半金属或类金属。
4. Chemical Reactions | 化学反应
A chemical reaction is a process in which atoms are rearranged to make new substances. Signs of a chemical change include a colour change, a temperature change (exothermic or endothermic), bubbles of gas appearing, or a precipitate (solid) forming.
化学反应是原子重新排列形成新物质的过程。化学变化的迹象包括颜色变化、温度变化（放热或吸热）、气泡产生或沉淀（固体）生成。
Reactants are the starting substances and products are what we end with. Mass is conserved during a reaction: the total mass of the products equals the total mass of the reactants. This is the law of conservation of mass.
反应物是起始的物质，产物是最终得到的物质。反应过程中质量守恒：产物的总质量等于反应物的总质量。这就是质量守恒定律。
magnesium + oxygen → magnesium oxide
镁 + 氧气 → 氧化镁
2Mg + O₂ → 2MgO
Word equations give the names of reactants and products, while symbol equations use chemical symbols and must be balanced so that each side has the same number of each type of atom.
文字方程式使用反应物和产物的名称，而符号方程式则用化学符号表示，并且必须配平，使每种原子的数目在两边相等。
5. Acids and Alkalis | 酸与碱
Acids are substances with a pH less than 7. They taste sour (though tasting laboratory chemicals is forbidden!) and include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Strong acids can be corrosive.
酸是 pH 值小于 7 的物质。它们尝起来有酸味（但实验室化学品严禁品尝！），包括盐酸（HCl）、硫酸（H₂SO₄）和硝酸（HNO₃）。强酸具有腐蚀性。
Bases are substances that neutralise acids. A base that dissolves in water is called an alkali. Alkalis have a pH greater than 7 and feel soapy. Examples include sodium hydroxide (NaOH) and potassium hydroxide (KOH).
碱是能中和酸的物质。可溶于水的碱称为可溶性碱（alkali）。可溶性碱的 pH 值大于 7，触感滑腻。例子有氢氧化钠（NaOH）和氢氧化钾（KOH）。
Indicators change colour to show whether a solution is acidic or alkaline. Litmus turns red in acid and blue in alkali. Universal indicator gives a full pH colour range from red (strong acid) through green (neutral) to purple (strong alkali).
指示剂通过变色显示溶液是酸性还是碱性。石蕊在酸中变红，在碱中变蓝。通用指示剂则展现出从红色（强酸）经绿色（中性）到紫色（强碱）的完整 pH 颜色范围。
6. Neutralisation | 中和反应
Neutralisation is the reaction between an acid and a base to form a salt and water. The pH moves towards 7 as the acid and base cancel each other out.
中和反应是酸与碱作用生成盐和水的反应。随着酸和碱相互抵消，pH 值趋向于 7。
HCl + NaOH → NaCl + H₂O
盐酸 + 氢氧化钠 → 氯化钠 + 水
The name of the salt comes from the acid and the metal in the base. Hydrochloric acid produces chloride salts, sulfuric acid produces sulfate salts, and nitric acid produces nitrate salts.
盐的名称来源于所用的酸和碱中的金属。盐酸生成氯化物盐，硫酸生成硫酸盐，硝酸生成硝酸盐。
Neutralisation has many uses: antacid tablets relieve indigestion by neutralising excess stomach acid, and lime (calcium oxide) is spread on acidic soil to raise the pH for better crop growth.
中和反应有许多实际应用：抗酸药片通过中和过多胃酸缓解消化不良，而石灰（氧化钙）施用在酸性土壤中可提高 pH 值，促进作物生长。
7. Separating Mixtures | 混合物的分离
Mixtures can be separated because the components are not chemically bonded. Filtration separates an insoluble solid from a liquid, using filter paper that lets liquid pass through but traps solid particles.
混合物能被分离是因为各组分并未化学结合。过滤用于分离不溶性固体与液体，利用滤纸让液体通过而截留固体颗粒。
Evaporation removes a solvent from a solution to leave the dissolved solid behind. Crystallisation goes a step further by producing well‑formed crystals of the solute.
蒸发是从溶液中除去溶剂，留下溶解的固体。结晶则更进一步，生成形状规则的溶质晶体。
Distillation separates a liquid from a solution by boiling it and then condensing the vapour. Simple distillation collects the pure liquid, while fractional distillation separates a mixture of liquids with different boiling points, such as crude oil fractions.
蒸馏通过煮沸溶液再冷凝蒸气来分离液体。简单蒸馏可收集纯液体；分馏则可分离沸点不同的液体混合物，比如原油的各个馏分。
Chromatography separates coloured substances (inks, food dyes) based on how well they travel along a stationary phase. The pattern of spots, called a chromatogram, helps identify the different components.
色谱法根据有色物质（墨水、食用色素）在固定相上移动的快慢来分离它们。形成的斑点图谱称为色谱图，有助于鉴别不同组分。
8. Metals and Non‑metals | 金属与非金属
Metals are usually shiny, good conductors of heat and electricity, malleable (can be hammered into sheets) and ductile (can be drawn into wires). Most are solid at room temperature; mercury is a notable liquid metal.
金属通常有光泽，是热和电的良导体，具有延展性（可锤成薄片）和可拉丝性。室温下大多数金属为固体；汞是一种显著的液态金属。
Non‑metals tend to be dull, brittle (if solid), poor conductors of heat and electricity, and often have low melting points. Many are gases at room temperature. Exceptions include graphite, a form of carbon that conducts electricity.
非金属往往无光泽、脆（若为固体）、不善于导热导电，且通常熔点较低。许多非金属在室温下是气体。例外包括石墨，这种碳的同素异形体能导电。
| Property | Metals | Non‑metals |
| Melting point | Usually high | Usually low |
| Conductivity | Good | Poor (except graphite) |
| Appearance | Shiny | Dull |
| Malleability | Malleable and ductile | Brittle if solid |
金属与非金属的典型性质对比表。
9. The Earth’s Atmosphere and Resources | 地球大气与资源
The atmosphere surrounding Earth is a mixture of gases. Nitrogen makes up about 78%, oxygen about 21%, and argon nearly 0.9%. Carbon dioxide (CO₂) accounts for roughly 0.04%, along with trace amounts of other gases and water vapour.
环绕地球的大气是一种气体混合物。氮气约占 78%，氧气约占 21%，氩气接近 0.9%。二氧化碳（CO₂）约 0.04%，同时还有微量其他气体和水蒸气。
Carbon dioxide is a greenhouse gas. It traps heat in the atmosphere, helping Earth stay warm enough for life. However, burning fossil fuels releases extra CO₂, which can enhance the greenhouse effect and lead to climate change.
二氧化碳是一种温室气体。它能将热量保留在大气中，使地球保持适合生命存在的温度。但燃烧化石燃料会释放额外的 CO₂，可能会增强温室效应并导致气候变化。
Natural resources include fossil fuels (coal, oil, natural gas), which are finite and non‑renewable. Renewable resources such as solar, wind and hydroelectric power offer more sustainable ways to generate energy. Chemists also design ways to recycle materials and reduce pollution.
自然资源包括化石燃料（煤、石油、天然气），它们是有限的且不可再生。太阳能、风能和水能等可再生能源提供了更可持续的能源方式。化学家还设计出回收材料和减少污染的方法。
10. Pure Substances and Impurities | 纯净物与杂质
A pure substance consists of only one type of particle – a single element or a single compound. Pure substances have sharp, fixed melting and boiling points. For example, pure water boils at exactly 100 °C and melts at 0 °C (at standard pressure).
纯净物只由一种粒子组成——可以是单一元素或单一化合物。纯净物具有清晰固定的熔点和沸点。例如，纯水在标准气压下恰好 100 °C 沸腾、0 °C 熔化。
Impurities lower the melting point and raise the boiling point, and also widen the melting and boiling ranges. This is why salt is spread on icy roads: dissolved salt lowers the freezing point of water, helping the ice melt.
杂质会降低熔点、升高沸点，并使熔沸范围变宽。这就是在结冰路面撒盐的原因：溶解的盐降低了水的凝固点，有助于冰融化。
Testing purity can be done by measuring melting and boiling points and comparing them with accepted values. A single spot on a chromatogram also suggests a pure substance, while multiple spots indicate a mixture.
纯度测试可通过测量熔点和沸点并与公认值比较来进行。色谱图上仅有一个斑点也说明是纯净物，而多个斑点则表明是混合物。
Published by TutorHao | Chemistry Revision Series | aleveler.com
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