📚 Year 7 CIE Chemistry: Core Knowledge at a Glance | Year 7 CIE 化学：核心知识点梳理
Welcome to this essential revision guide for Year 7 CIE Chemistry. Here we cover the key concepts, from states of matter and particle theory to acids, alkalis, and chemical reactions. Mastering these fundamentals will build a strong foundation for your scientific journey.
欢迎阅读 Year 7 CIE 化学的核心复习指南。我们涵盖物质状态与粒子理论、酸与碱、化学反应等关键概念。掌握这些基础知识将为你的科学学习打下坚实基础。
1. States of Matter and the Particle Model | 物质的三态与粒子模型
All substances are made of tiny particles. The three common states of matter are solid, liquid and gas. The arrangement and movement of these particles determine the properties of each state.
所有物质都由微小粒子构成。物质的三种常见状态是固态、液态和气态。粒子的排列方式和运动决定了每种状态的性质。
In solids, particles are packed closely in a regular pattern. They vibrate in fixed positions but cannot move past each other. This gives solids a fixed shape and volume.
在固体中，粒子紧密排列成规则的图案。它们在固定位置上振动，但无法越过彼此。这使得固体有固定的形状和体积。
In liquids, particles are still close together but are arranged irregularly. They can slide past one another, so liquids have a fixed volume but take the shape of their container.
在液体中，粒子仍然紧密但排列不规则。它们可以相互滑动，因此液体有固定的体积，但会呈现容器的形状。
In gases, particles are far apart and move rapidly in all directions. They have no fixed shape or volume – they spread out to fill any container.
在气体中，粒子间距很大并快速向各个方向运动。它们没有固定的形状或体积，会扩散并充满整个容器。
| State / 状态 | Particle arrangement / 粒子排列 | Movement / 运动 | Shape & volume / 形状与体积 |
|---|---|---|---|
| Solid 固体 | Regular, very close 规则，极近 | Vibrate only 仅振动 | Fixed shape, fixed volume 固定形状，固定体积 |
| Liquid 液体 | Irregular, close 不规则，紧密 | Slide past each other 相互滑动 | Takes shape of container, fixed volume 形状随容器，固定体积 |
| Gas 气体 | Random, far apart 随机，相距远 | Move rapidly in all directions 快速向四面八方运动 | No fixed shape or volume 无固定形状或体积 |
2. Changes of State | 物态变化
When a substance is heated or cooled, its particles gain or lose energy. This causes changes of state. The main processes are melting, freezing, boiling, evaporation and condensation.
当物质受热或冷却时，粒子获得或失去能量，从而引起物态变化。主要过程包括熔化、凝固、沸腾、蒸发和凝结。
Melting is the change from solid to liquid. The particles gain energy, vibrate more vigorously, and break free from their fixed positions. The temperature at which this occurs is the melting point.
熔化是从固体变为液体。粒子获得能量，振动更剧烈，摆脱固定位置。发生这一变化时的温度叫做熔点。
Boiling occurs when a liquid turns into a gas throughout the liquid, at a specific temperature called the boiling point. Evaporation, by contrast, happens only at the surface and can occur at any temperature.
沸腾是液体在特定温度（沸点）整体变为气体的过程。而蒸发只发生在液体表面，可以在任何温度下进行。
Condensation is the change from gas to liquid. Particles lose energy, move closer together, and form a liquid. Freezing is the reverse of melting – liquid turns into solid as particles arrange into a fixed pattern.
凝结是从气体变为液体，粒子失去能量，相互靠近形成液体。凝固是熔化的逆过程——液体变为固体，粒子排列成固定的图案。
3. Diffusion and Particle Movement | 扩散与粒子运动
Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. It occurs because particles in liquids and gases are in constant, random motion.
扩散是粒子从高浓度区域向低浓度区域运动的过程。它能发生是因为液体和气体中的粒子处于持续、无规则的运动中。
Gases diffuse faster than liquids because their particles move more quickly and have larger spaces between them. Heating a substance increases the rate of diffusion as particles gain kinetic energy.
气体的扩散速度比液体快，因为气体粒子运动更快且间距更大。加热物质可以加快扩散速率，因为粒子获得更多动能。
An example of diffusion is when a drop of ink spreads out evenly in a beaker of water without stirring. The ink particles mix with water particles until they are uniformly distributed.
扩散的一个例子是：一滴墨水在烧杯中的水里无需搅拌就会均匀散开。墨水粒子与水粒子混合，直到分布均匀。
4. Elements, Compounds and Mixtures | 元素、化合物与混合物
An element is a substance made of only one type of atom. Examples include oxygen (O), iron (Fe) and gold (Au). Each element is listed on the Periodic Table.
元素是由同一种原子组成的物质，例如氧 (O)、铁 (Fe) 和金 (Au)。每种元素都列在元素周期表中。
A compound is a substance formed when two or more different elements chemically combine in a fixed ratio. For example, water (H₂O) is a compound of hydrogen and oxygen. The properties of a compound are different from those of its constituent elements.
化合物是由两种或多种不同元素以固定比例通过化学结合形成的物质。例如，水 (H₂O) 是氢和氧的化合物。化合物的性质与组成它的元素不同。
A mixture consists of two or more substances physically mixed but not chemically joined. Air is a mixture of nitrogen, oxygen, argon and other gases. The components of a mixture can be separated by physical methods.
混合物由两种或多种物质物理混合而成，未发生化学结合。空气是氮气、氧气、氩气和其他气体的混合物。混合物的成分可通过物理方法分离。
5. The Periodic Table: Metals and Non-metals | 周期表：金属与非金属
The Periodic Table arranges all known elements in order of increasing atomic number. Metals are found on the left and centre, while non-metals are located on the right.
元素周期表按原子序数递增的顺序排列所有已知元素。金属位于左侧和中部，非金属位于右侧。
Metals are typically shiny, good conductors of heat and electricity, malleable (can be hammered into sheets) and ductile (can be drawn into wires). Examples include copper, aluminium and zinc.
金属通常有光泽，是热和电的良导体，具有延展性（可锤打成薄片）和韧性（可拉成丝）。例如铜、铝和锌。
Non-metals are usually dull, brittle when solid, and poor conductors. Many are gases at room temperature, such as oxygen and nitrogen. Carbon and sulfur are solid non-metals.
非金属通常暗淡，固态时质脆，导热导电性差。许多非金属在室温下是气体，如氧气和氮气。碳和硫是固态非金属。
6. Separation Techniques: Filtration, Evaporation and Distillation | 分离技术：过滤、蒸发与蒸馏
Filtration is used to separate an insoluble solid from a liquid. The mixture is poured through filter paper; the solid remains as residue, and the liquid passes through as filtrate.
过滤用于分离不溶性固体和液体。混合物倒入滤纸，固体留在滤纸上成为滤渣，液体通过成为滤液。
Evaporation can separate a dissolved solid from a solution. The solution is heated so the liquid evaporates, leaving the solid behind. This works for salt from salt water, but the liquid is lost.
蒸发可将溶解的固体从溶液中分离出来。加热溶液使液体蒸发，固体析出。此法可从盐水中获得食盐，但液体会损失。
Simple distillation is used to separate a liquid from a solution. The solution is boiled, the vapour is cooled in a condenser, and the pure liquid (distillate) is collected. It preserves both the solvent and the solute.
简单蒸馏用于从溶液中分离液体。将溶液煮沸，蒸气在冷凝器中冷却，收集到纯净液体（馏出液）。此方法可同时保留溶剂和溶质。
7. Chromatography | 色谱法
Chromatography is a technique used to separate mixtures of coloured substances, such as inks or food dyes. It relies on the different solubilities of the components in a solvent.
色谱法是一种用于分离有色混合物（如墨水或食用色素）的技术。它依靠各组分在溶剂中溶解度的差异。
In paper chromatography, a spot of the mixture is placed near the bottom of a piece of chromatography paper. The paper is dipped in a solvent, which travels up and carries the dyes with it. Different substances move at different rates, creating separate spots.
在纸色谱法中，将混合物点样在色谱纸接近底部的位置。纸的下端浸入溶剂，溶剂上行并携带染料。不同物质移动速率不同，形成分离的斑点。
A more soluble substance travels further up the paper. We can compare the Rf value (distance moved by substance ÷ distance moved by solvent) to identify unknown substances.
溶解度越大的物质在纸上迁移得越远。我们可以比较 Rf 值（物质移动距离 ÷ 溶剂移动距离）来鉴别未知物质。
8. Physical and Chemical Changes | 物理变化与化学变化
A physical change alters the form or state of a substance but does not produce a new substance. Melting ice, dissolving sugar in water, and tearing paper are all physical changes. They are usually easy to reverse.
物理变化改变物质的形式或状态，但不产生新物质。冰融化成水、糖溶于水、撕纸都是物理变化。这些变化通常容易逆转。
A chemical change (or chemical reaction) results in the formation of one or more new substances. Signs of a chemical change include a colour change, fizzing (gas production), a temperature change, or the formation of a precipitate.
化学变化（或化学反应）会生成一种或多种新物质。化学变化的标志包括颜色改变、冒泡（产生气体）、温度变化或生成沉淀。
Burning wood, rusting of iron, and cooking an egg are examples of chemical changes. They are usually difficult or impossible to reverse.
木材燃烧、铁生锈和煮鸡蛋都是化学变化的例子。它们通常难以或无法逆转。
9. Acids and Alkalis | 酸与碱
Acids are substances that release hydrogen ions (H⁺) in solution. They taste sour and can be corrosive. Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃).
酸是在溶液中能释放氢离子 (H⁺) 的物质。它们有酸味，可能具有腐蚀性。实验室常用酸包括盐酸 (HCl)、硫酸 (H₂SO₄) 和硝酸 (HNO₃)。
Alkalis are soluble bases that release hydroxide ions (OH⁻) in water. They feel soapy and can also be corrosive. Examples are sodium hydroxide (NaOH) and potassium hydroxide (KOH).
碱是可溶性的碱，在水中释放氢氧根离子 (OH⁻)。它们有滑腻感，同样可能具有腐蚀性。例子有氢氧化钠 (NaOH) 和氢氧化钾 (KOH)。
isation reaction occurs, producing a salt and water. For example: HCl + NaOH → NaCl + H₂O.
当酸与碱反应时，发生中和反应，生成盐和水。例如：HCl + NaOH → NaCl + H₂O。
10. Indicators and the pH Scale | 指示剂与pH值
Indicators are substances that change colour depending on whether a solution is acidic or alkaline. Litmus paper turns red in acids and blue in alkalis. Universal indicator gives a range of colours to show the strength.
指示剂是根据溶液酸性或碱性改变颜色的物质。石蕊试纸遇酸变红，遇碱变蓝。通用指示剂能呈现一系列颜色以显示酸碱强弱。
The pH scale ranges from 0 to 14. A pH less than 7 is acidic, pH 7 is neutral (pure water), and pH greater than 7 is alkaline. The lower the pH, the stronger the acid; the higher the pH, the stronger the alkali.
pH 范围从 0 到 14。pH 小于 7 为酸性，pH 等于 7 为中性（纯水），pH 大于 7 为碱性。pH 越低酸性越强，pH 越高碱性越强。
Using universal indicator, strong acids appear red (pH 0-2), weak acids appear orange or yellow (pH 3-6), neutral is green (pH 7), weak alkalis appear blue (pH 8-11), and strong alkalis appear violet (pH 12-14).
用通用指示剂测试时，强酸呈红色 (pH 0-2)，弱酸呈橙色或黄色 (pH 3-6)，中性呈绿色 (pH 7)，弱碱呈蓝色 (pH 8-11)，强碱呈紫色 (pH 12-14)。
11. Reactions of Acids with Metals and Carbonates | 酸与金属及碳酸盐的反应
eacts with hydrochloric acid to form magnesium chloride and hydrogen: Mg + 2HCl → MgCl₂ + H₂.
酸能与许多金属反应生成盐和氢气。通用文字方程式为：酸 + 金属 → 盐 + 氢气。例如，镁与盐酸反应生成氯化镁和氢气：Mg + 2HCl → MgCl₂ + H₂。
You can test for hydrogen gas by holding a lit splint at the mouth of the test tube. If hydrogen is present, it burns with a 'squeaky pop' sound.
检验氢气的方法是将点燃的木条靠近试管口，若有氢气存在，会发出 "噗" 的一声（爆鸣声）。
ic acid → calcium chloride + water + carbon dioxide. Carbon dioxide turns limewater milky.
酸还能与金属碳酸盐反应，生成盐、水和二氧化碳。例如：碳酸钙 + 盐酸 → 氯化钙 + 水 + 二氧化碳。二氧化碳能使石灰水变浑浊。
12. Air, Combustion and Rusting | 空气、燃烧与生锈
Air is a mixture of gases: roughly 78% nitrogen, 21% oxygen, 0.9% argon, and small amounts of carbon dioxide and other gases. Oxygen is essential for combustion and respiration.
空气是一种气体混合物：约 78% 氮气、21% 氧气、0.9% 氩气以及少量的二氧化碳和其他气体。氧气对燃烧和呼吸至关重要。
ation for complete combustion of a hydrocarbon is: fuel + oxygen → carbon dioxide + water.
燃烧是一种化学反应，燃料在氧气中燃烧并释放热量和光。碳氢化合物完全燃烧的通用方程式为：燃料 + 氧气 → 二氧化碳 + 水。
Rusting is the corrosion of iron in the presence of both oxygen and water. It forms hydrated iron(III) oxide (rust). Rusting is a chemical change that weakens the metal. Painting or oiling can prevent rust by stopping oxygen and water reaching the surface.
生锈是铁在氧气和水共同存在下的腐蚀过程，生成水合氧化铁（铁锈）。生锈是化学变化，会削弱金属。涂漆或上油可以通过隔绝氧气和水来防止生锈。
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