📚 Year 7 Edexcel Chemistry: Core Concepts Review | Year 7 Edexcel 化学：核心知识点梳理
In Year 7 Edexcel Chemistry, you begin to uncover the invisible world of atoms and molecules. This article brings together all the essential ideas you need to master, from the particle model and elements to acids and combustion. Each section pairs a clear English explanation with its Chinese counterpart to make revision simple and effective.
在 Year 7 Edexcel 化学课程中，你开始探索原子与分子的不可见世界。本文汇集了你需要掌握的所有核心概念，从粒子模型、元素到酸和燃烧。每个部分都用清晰的英文解释配以对应的中文讲解，帮助你将复习变得简单高效。
1. States of Matter and the Particle Model | 物质状态与粒子模型
Matter exists in three main states: solid, liquid and gas. In solids, particles are packed tightly in a regular pattern and can only vibrate in fixed positions. This gives solids a fixed shape and volume.
物质主要以三种状态存在：固态、液态和气态。在固体中，粒子排列紧密且规则，只能在固定位置振动。这使得固体拥有固定的形状和体积。
In liquids, particles are still close together but can move past one another. They take the shape of the container but have a fixed volume.
在液体中，粒子依然彼此靠近，但能够相对滑动。它们会容器的形状而改变形状，但体积保持不变。
In gases, particles are far apart and move rapidly in all directions. Gases have no fixed shape or volume and can be compressed easily.
在气体中，粒子相距很远，快速地向各个方向运动。气体没有固定的形状和体积，而且容易被压缩。
The simple particle model explains these behaviours: adding thermal energy makes particles vibrate or move more, causing expansion or a change of state. Melting and boiling occur when the particles gain enough energy to overcome the forces holding them together.
简单的粒子模型解释了这些行为：输入热能会使粒子振动或运动更剧烈，导致膨胀或状态变化。当粒子获得足够能量摆脱将其束缚在一起的力时，就会发生熔融与沸腾。
Solid → liquid (melting) | Liquid → gas (boiling/evaporation) | Gas → liquid (condensing)
固态 → 液态（熔化） | 液态 → 气态（沸腾/蒸发） | 气态 → 液态（冷凝）
2. Atoms, Elements and Compounds | 原子、元素与化合物
All substances are made of tiny particles called atoms. An element is a substance made from only one type of atom. There are about 118 known elements, and each one has its own chemical symbol, such as H for hydrogen or O for oxygen.
所有物质都由名为原子的微小粒子构成。元素是由仅一种原子组成的物质。已知元素大约有118种，每一种都有自己独特的化学符号，例如 H 代表氢，O 代表氧。
When two or more different elements chemically combine, a compound is formed. The properties of a compound are usually completely different from the elements that make it. For example, sodium (a reactive metal) and chlorine (a poisonous gas) combine to form sodium chloride, which is common table salt.
当两种或更多不同元素发生化学结合时，就形成了化合物。化合物的性质通常与构成它的元素完全不同。例如，钠（一种活泼金属）和氯（一种有毒气体）结合生成氯化钠，也就是普通的食盐。
You can represent elements and compounds using chemical formulae. The formula of a compound shows the symbols of the elements and the ratio of atoms. For instance, H₂O means two hydrogen atoms bonded to one oxygen atom.
你可以用化学式来表示元素和化合物。化合物的化学式显示了元素符号以及原子的比例。例如，H₂O 表示两个氢原子与一个氧原子结合。
3. 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. The vertical columns are called groups, and the horizontal rows are called periods. Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell.
元素周期表是一张按照原子序数递增顺序排列所有已知元素的图表。竖列称为族，横行称为周期。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目相同。
Metals are found on the left and centre of the table, while non-metals are on the right. A stepped line divides the metals from the non-metals. Year 7 learners should be able to locate common elements like carbon, oxygen, iron and copper.
金属位于周期表的左侧和中部，非金属位于右侧。一条锯齿状斜线将金属与非金属分开。Year 7 的学生应该能够找到常见元素如碳、氧、铁和铜的位置。
Important groups to remember include Group 1 (alkali metals), Group 7 (halogens) and Group 0 (noble gases). Noble gases are very unreactive because they already have a full outer shell of electrons.
需要记住的重要族包括第 1 族（碱金属）、第 7 族（卤素）以及第 0 族（稀有气体）。稀有气体极不活泼，因为它们已经具有完整的最外层电子结构。
4. Chemical Changes vs Physical Changes | 化学变化与物理变化
A physical change occurs when the state or appearance of a substance alters, but no new substance is made. Examples include melting ice, boiling water and dissolving sugar. These changes are usually easy to reverse.
当物质的状态或外观发生改变，但没有生成新物质时，就发生了物理变化。例如冰融化、水沸腾和糖溶解。这些变化通常容易逆转。
A chemical change forms one or more new substances. Signs of a chemical reaction include a colour change, gas production (bubbles), temperature change, or the appearance of a solid (precipitate). Burning wood, frying an egg and rusting iron are all chemical changes that are often difficult to reverse.
化学变化会产生一种或多种新物质。化学反应的迹象包括颜色变化、产生气体（气泡）、温度变化或固体（沉淀）的出现。木头燃烧、煎鸡蛋和铁生锈都属于通常难以逆转的化学变化。
It is important to remember that mass is conserved in both physical and chemical changes. In a chemical reaction, the total mass of the reactants equals the total mass of the products.
需谨记的是，无论物理变化还是化学变化，质量都是守恒的。在化学反应中，反应物的总质量等于生成物的总质量。
5. Separation Techniques (Part 1) | 分离技术（一）
Mixtures contain two or more substances that are not chemically joined. We can separate mixtures using physical methods. Filtration is used to separate an insoluble solid from a liquid. A filter paper retains the solid residue while the liquid (filtrate) passes through.
混合物包含两种或更多没有通过化学键结合的物质。我们可以用物理方法分离混合物。过滤用于将不溶性固体从液体中分离出来。滤纸截留固体残渣，液体（滤液）则通过滤纸。
Evaporation and crystallisation separate a soluble solid from a solution. Heating the solution causes the solvent to evaporate, leaving the solid behind. For crystals, the solution is heated gently until crystals begin to form, then allowed to cool slowly.
蒸发和结晶用于从溶液中分离可溶性固体。加热溶液会使溶剂蒸发，留下固体。若要获得晶体，则需将溶液缓慢加热至晶体开始析出，再让其慢慢冷却。
Simple distillation uses evaporation followed by condensation to obtain a pure liquid from a solution. The solution is boiled, and the vapour is cooled and collected as a distillate. This technique is commonly used to produce pure water from salt water.
简单蒸馏利用了蒸发后冷凝的原理，从溶液中获得纯净液体。将溶液煮沸，蒸气经冷却后作为馏出液收集。这种技术常用于从盐水中制取纯水。
6. Separation Techniques (Part 2) | 分离技术（二）
Paper chromatography is used to separate mixtures of coloured substances, such as inks or food dyes. A small spot of the mixture is placed on chromatography paper and dipped into a solvent. The different substances travel up the paper at different speeds, producing a chromatogram.
纸色谱法用于分离有色物质的混合物，如墨水或食品染料。将一小点混合物点在色谱纸上并浸入溶剂中，不同的物质以不同的速度沿纸上移，形成色谱图。
Fractional distillation is a more advanced technique for separating a mixture of liquids with different boiling points, such as crude oil or fermented liquid. In Year 7, the focus is on recognising that it works because each liquid boils and condenses at a different temperature.
分馏是一种更高级的技术，用于分离不同沸点的液体混合物，比如原油或发酵液。在 Year 7 阶段，重点是理解其原理：因为每种液体在不同温度下沸腾与冷凝。
Magnetic separation uses a magnet to remove magnetic materials like iron filings from a mixture. Sieving separates solids of different particle sizes. These techniques remind us that separation methods depend on the physical properties of the components in the mixture.
磁分离法利用磁铁去除混合物中的磁性材料，如铁屑。过筛则根据颗粒大小分离固体。这些技术提醒我们，分离方法取决于混合物中各组分的物理性质。
7. Acids and Alkalis | 酸与碱
Acids are substances with a sour taste that turn blue litmus paper red. Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Many household items like citrus fruits and vinegar contain weak acids.
酸是具有酸味并且能让蓝色石蕊试纸变红的物质。常见的实验室酸有盐酸（HCl）、硫酸（H₂SO₄）和硝酸（HNO₃）。许多家居用品如柑橘类水果和醋都含有弱酸。
Alkalis are soluble bases that feel soapy and turn red litmus paper blue. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are common alkalis. Household cleaners often contain alkalis because they are effective at removing grease.
碱是可溶的碱性物质，触感滑腻，能让红色石蕊试纸变蓝。氢氧化钠（NaOH）和氢氧化钾（KOH）是常见的碱。家用清洁剂通常含有碱，因为它们能有效去除油污。
An alkali is a special type of base that dissolves in water to release hydroxide ions (OH⁻). In Year 7, we use the term alkali for any soluble base. Safety is extremely important when working with acids and alkalis, as they can be corrosive.
碱是能溶于水并释放氢氧根离子（OH⁻）的特殊类型的碱。在 Year 7 阶段，我们用碱来指代任何可溶性的碱性物质。处理酸和碱时，安全至关重要，因为它们可能具有腐蚀性。
8. pH Scale and Indicators | pH 标度与指示剂
The pH scale runs from 0 to 14 and tells us how acidic or alkaline a solution is. A pH less than 7 is acidic; a pH of 7 is neutral (like pure water); and a pH greater than 7 is alkaline. The lower the pH, the stronger the acid; the higher the pH, the stronger the alkali.
pH 标度范围从 0 到 14，用来表示溶液的酸碱性。pH 值小于 7 为酸性；pH 值等于 7 为中性（如纯水）；pH 值大于 7 为碱性。pH 越低酸性越强；pH 越高碱性越强。
Indicators are substances that change colour depending on the pH. Litmus is a simple indicator that turns red in acid and blue in alkali. Universal indicator is a mixture of indicators that gives a range of colours across the whole pH scale, from red for strong acid to purple for strong alkali.
指示剂是会随 pH 不同而改变颜色的物质。石蕊是一种简单的指示剂，遇酸变红、遇碱变蓝。通用指示剂则是多种指示剂的混合物，可在整个 pH 范围显示出从红（强酸）到紫（强碱）的多种颜色。
When testing unknown solutions in the lab, you can add a few drops of universal indicator and compare the colour to a colour chart. This gives a numerical pH value and helps you decide whether the solution is acidic, neutral or alkaline.
在实验室检测未知溶液时，你可以滴入几滴通用指示剂，再将颜色与色卡进行对比。这样你就可以得到 pH 数值，并判断溶液是酸性、中性还是碱性。
9. Reactions of Acids | 酸的反应
Acids react with many other substances. When an acid reacts with a metal, a salt and hydrogen gas are produced. The general word equation is:
酸能与许多其他物质发生反应。酸与金属反应时，会生成盐和氢气。通用的文字方程式为：
acid + metal → salt + hydrogen
酸 + 金属 → 盐 + 氢气
For example, hydrochloric acid and magnesium give magnesium chloride and hydrogen bubbles. We test for hydrogen using a lit splint; if hydrogen is present, it burns with a squeaky pop.
例如，盐酸与镁反应生成氯化镁并产生氢气气泡。我们用点燃的木条来检验氢气；如果有氢气存在，它会发出爆鸣声。
Acids also neutralise bases and alkalis to form a salt and water. The general equation is:
酸也能与碱及碱性物质发生中和反应，生成盐和水。通用方程式为：
acid + alkali → salt + water
酸 + 碱 → 盐 + 水
Hydrochloric acid reacts with sodium hydroxide to produce sodium chloride and water. Neutralisation is an exothermic reaction, meaning it releases heat. It has many uses, including treating acid indigestion and adjusting soil pH.
盐酸与氢氧化钠反应生成氯化钠和水。中和反应是放热反应，会释放热量。它有许多用途，包括治疗胃酸过多和调节土壤 pH 值。
10. The Air and Combustion | 空气与燃烧
Air is a mixture of gases. About 78% is nitrogen, 21% is oxygen, and the remaining 1% consists of argon, carbon dioxide and other trace gases. Oxygen is the reactive component that supports combustion and respiration.
空气是多种气体的混合物。大约 78% 是氮气，21% 是氧气，剩下的 1% 包括氩气、二氧化碳和其他痕量气体。氧气是能够支持燃烧和呼吸的活性组分。
Combustion, or burning, is a chemical reaction in which a substance reacts with oxygen, releasing energy as heat and light. For complete combustion of hydrocarbons such as methane (CH₄), the products are carbon dioxide (CO₂) and water (H₂O):
燃烧是一种化学反应，物质与氧气反应，释放出热和光能。对于甲烷（CH₄）等碳氢化合物而言，完全燃烧的产物是二氧化碳（CO₂）和水（H₂O）：
CH₄ + 2O₂ → CO₂ + 2H₂O
CH₄ + 2O₂ → CO₂ + 2H₂O
When there is insufficient oxygen, incomplete combustion occurs, producing carbon monoxide (CO) or even solid carbon (soot). Carbon monoxide is a toxic gas that can be lethal.
当氧气不足时，会发生不完全燃烧，生成一氧化碳（CO）甚至是固体碳（炭黑）。一氧化碳是一种有毒气体，可能致命。
Rusting is a slow oxidation reaction between iron, oxygen and water. It forms hydrated iron oxide, Fe₂O₃·xH₂O. Covering iron with paint, oil or a sacrificial coating of zinc (galvanising) can prevent rusting.
生锈是铁与氧气及水之间发生的一种缓慢氧化反应，形成水合氧化铁 Fe₂O₃·xH₂O。用油漆、油或牺牲性镀锌层（电镀）覆盖铁，可以防止生锈。
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