📚 Year 7 Cambridge Chemistry: Full Syllabus Breakdown | Year 7 Cambridge 化学：课程大纲全面解析
Chemistry in Year 7 introduces the fundamental ideas of matter, particles, mixtures, and simple chemical reactions. The Cambridge Lower Secondary Science curriculum builds a strong foundation by linking everyday observations to scientific models. This breakdown covers every topic in the syllabus, explaining key concepts, vocabulary, and practical skills that students need to master.
七年级化学课程引入了物质、粒子、混合物和简单化学反应的基本概念。剑桥初中科学课程通过将日常观察与科学模型联系起来，为学生们打下坚实的基础。这份解析涵盖了课程大纲中的所有主题，解释了学生需要掌握的关键概念、术语和实验技能。
1. The Particle Model of Matter | 物质粒子模型
All substances are made up of tiny particles that are in constant motion. The particle model helps explain why solids have a fixed shape, liquids flow and gases spread out. The particles in a solid are tightly packed in a regular arrangement and only vibrate in fixed positions. In liquids, particles are close together but can slide past one another, allowing liquids to flow and take the shape of their container. Gas particles are far apart and move randomly at high speeds, which is why gases can be compressed and fill any space.
所有物质都由不断运动的微小粒子构成。粒子模型有助于解释为什么固体有固定形状、液体会流动、气体会扩散。固体中的粒子紧密排列且规则，只能在固定位置振动。液体中粒子同样紧密，但可以相互滑动，使液体能够流动并呈现容器的形状。气体粒子相距很远，高速随机运动，因此气体可以被压缩并充满任何空间。
The spaces between particles change during expansion and contraction. Heating increases the kinetic energy of particles, making them move faster and spread further apart; this causes the material to expand. Cooling reduces the energy, bringing particles closer together and causing contraction. The mass of a substance does not change during these processes because the number of particles remains the same.
粒子间的距离会在膨胀和收缩过程中发生变化。加热增加了粒子的动能，使它们运动更快、间距更大，从而导致材料膨胀。冷却降低了能量，粒子更靠近，引发收缩。在这些过程中，物质的质量不会改变，因为粒子总数保持不变。
2. States of Matter and Changes of State | 物质状态与状态变化
Matter exists in three main states: solid, liquid and gas. Each state can change into another through physical processes that involve heat energy. Melting is the change from solid to liquid, and freezing is the reverse. Evaporation and boiling change a liquid into a gas, while condensation turns a gas back into a liquid. Sublimation occurs when a solid changes directly into a gas, such as solid carbon dioxide (dry ice) turning into carbon dioxide gas.
物质主要以三种状态存在：固态、液态和气态。每种状态都可以通过涉及热能的物理过程转变为另一种状态。熔化是从固态变为液态，凝固是逆过程。蒸发和沸腾将液体转变为气体，而冷凝则将气体转变回液体。升华是指固体直接转变为气体，例如固态二氧化碳（干冰）变成二氧化碳气体。
During a change of state, the temperature remains constant even though heat is being added or removed. This is because the energy is used to break or form the forces between particles rather than increase their kinetic energy. For water, melting occurs at 0 °C and boiling at 100 °C under standard atmospheric pressure. The particle model clearly illustrates why stronger forces in solids require more energy to change state.
在状态变化过程中，尽管在加热或移除热量，温度却保持不变。这是因为能量用于打破或形成粒子之间的作用力，而不是增加它们的动能。在标准大气压下，水的熔点是 0 °C，沸点是 100 °C。粒子模型清楚地说明了为什么固体中更强的力需要更多能量来改变状态。
3. Diffusion and Brownian Motion | 扩散与布朗运动
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration. It occurs in liquids and gases because the particles are free to move. A common example is the smell of perfume spreading across a room. Diffusion does not happen in solids because the particles are locked in place. The rate of diffusion increases with temperature because particles gain more kinetic energy and move faster.
扩散是粒子从高浓度区域向低浓度区域的净移动。它发生在液体和气体中，因为粒子可以自由运动。一个常见的例子是香水气味在房间中扩散。扩散在固体中不会发生，因为粒子被固定在位置上。扩散速率随温度升高而增加，因为粒子获得更多动能，运动更快。
Brownian motion is the random, jerky movement of tiny visible particles, such as smoke or pollen grains, when suspended in a fluid. This movement is caused by collisions with the invisible, fast-moving particles of the fluid. Observing Brownian motion under a microscope provides evidence for the particle theory and the constant motion of particles in liquids and gases.
布朗运动是悬浮在流体中的微小可见粒子（如烟雾或花粉粒）的无规则、急动运动。这种运动是由与流体中看不见的、快速运动的粒子碰撞引起的。在显微镜下观察布朗运动为粒子理论以及液体和气体中粒子持续运动的观点提供了证据。
4. Solutions and Solubility | 溶液与溶解度
A solution is formed when a solute dissolves in a solvent. In salt water, salt is the solute and water is the solvent. The mixture is clear and homogeneous, meaning the particles are evenly distributed. Solubility is the maximum mass of solute that can dissolve in 100 g of solvent at a given temperature. Different substances have different solubilities, and solubility curves show how solubility changes with temperature.
当溶质溶解在溶剂中时就形成了溶液。在盐水中，盐是溶质，水是溶剂。混合物是澄清且均一的，意味着粒子均匀分布。溶解度是指在给定温度下，100 g 溶剂中可以溶解的最大溶质质量。不同的物质有不同的溶解度，溶解度曲线显示了溶解度如何随温度变化。
In most cases, solids become more soluble as temperature increases. Gases, however, become less soluble in water when heated, which is why fizzy drinks go flat more quickly when warm. Stirring and increasing the surface area of the solute speed up dissolving but do not change the final amount of solute that can dissolve. A saturated solution contains the maximum amount of dissolved solute at that temperature; any extra solute will simply settle at the bottom.
在大多数情况下，固体随着温度升高而溶解度增加。然而，气体在水中的溶解度随加热而降低，这就是为什么温热的汽水会更快变平。搅拌和增加溶质的表面积可以加快溶解速度，但不会改变最终能溶解的溶质量。饱和溶液在特定温度下包含了最大溶解量的溶质；任何额外的溶质将只是沉在底部。
5. Pure Substances and Mixtures | 纯物质与混合物
A pure substance contains only one type of particle and has a fixed melting point and boiling point. For example, pure water melts at exactly 0 °C and boils at 100 °C. A mixture consists of two or more different substances that are physically combined but not chemically joined. Mixtures can usually be separated by physical means, and they melt or boil over a range of temperatures rather than at a single fixed point.
纯物质只包含一种类型的粒子，具有固定的熔点和沸点。例如，纯水在 0 °C 精确熔化，在 100 °C 沸腾。混合物由两种或多种不同物质物理结合而成，但未发生化学键合。混合物通常可以通过物理方法分离，并且它们在一个温度范围内熔化或沸腾，而不是在单个固定点。
In everyday life, most materials are mixtures. Air is a mixture of gases, mainly nitrogen and oxygen. Sea water is a mixture of water, salts and dissolved gases. Understanding the difference between pure substances and mixtures is essential when choosing a separation technique, as some methods work best depending on the physical properties of the components involved.
在日常生活中，大多数材料都是混合物。空气是气体混合物，主要成分是氮气和氧气。海水是水、盐和溶解气体的混合物。理解纯物质和混合物之间的区别对于选择分离技术至关重要，因为某些方法的效果取决于所涉及组分的物理性质。
6. Separation Techniques: Filtration and Evaporation | 分离技术：过滤与蒸发
Filtration is used to separate an insoluble solid from a liquid. The mixture is poured through filter paper in a funnel; the solid residue is left on the paper while the liquid filtrate passes through. This technique relies on the difference in particle size. An example is separating sand from water. Filtration cannot be used to separate dissolved solids like salt from solutions.
过滤用于将不溶固体从液体中分离出来。混合物通过漏斗中的滤纸倾倒；固体残渣留在纸上，液体滤液则通过。该技术依赖于粒子大小的差异。一个例子是从水中分离沙子。过滤不能用于从溶液中分离已经溶解的固体，如盐。
Evaporation is a simple method to obtain a dissolved solid from a solution. The solution is heated in an evaporating dish so that the solvent boils off, leaving the solid behind. This works well for substances like salt, but it cannot recover the solvent. Crystallisation is a gentler method where the solution is heated to evaporate some solvent and then left to cool, allowing crystals to form; this produces pure solid crystals while reducing the loss of the solvent.
蒸发是从溶液中获取已溶解固体的简单方法。溶液在蒸发皿中加热，使得溶剂沸腾离去，留下固体。这对像盐这样的物质很有效，但不能回收溶剂。结晶是一种更温和的方法：将溶液加热蒸发部分溶剂，然后静置冷却，让晶体形成；这样可以产生纯的固态晶体，同时减少溶剂的损失。
7. Separation Techniques: Distillation and Chromatography | 分离技术：蒸馏与色谱
Distillation separates a solvent from a solution or separates liquids with different boiling points. In simple distillation, a solution is heated, the solvent vapourises, and then it is cooled and condensed back into a liquid in a condenser. This is used to obtain pure water from salt water. Fractional distillation is used for mixtures of miscible liquids, such as ethanol and water, using a fractionating column to separate the components as they condense at different heights.
蒸馏用于从溶液中分离溶剂，或分离沸点不同的液体。在简单蒸馏中，溶液被加热，溶剂蒸发，然后被冷却并在冷凝管中重新冷凝为液体。这被用来从盐水中获得纯水。分馏用于可混溶液体混合物，如乙醇和水，使用分馏柱在不同高度冷凝从而分离组分。
Chromatography separates small amounts of dissolved substances based on how they travel across a stationary phase. In paper chromatography, a spot of mixture is placed on a pencil line near the bottom of chromatography paper. The paper is dipped in a solvent; as the solvent moves up, the different substances are carried at different rates and form separate spots. The technique can be used to identify colours in ink, food dyes and even amino acids. Each separated component has a specific Rf value (retention factor) calculated by distance moved by substance divided by distance moved by solvent.
色谱法根据物质在固定相中的移动方式分离少量溶解物质。在纸色谱中，混合物的斑点被点在色谱纸底部附近的铅笔线上。纸浸入溶剂中；随着溶剂上移，不同的物质以不同的速率被携带并形成独立的斑点。这项技术可用于鉴定墨水、食用色素甚至氨基酸中的颜色。每个分离组分都有特定的 Rf 值（保留因子），由物质移动距离除以溶剂移动距离计算得出。
8. Acids and Alkalis | 酸与碱
Acids are substances that taste sour and are corrosive. Common examples include citric acid in lemons, acetic acid in vinegar and hydrochloric acid in the laboratory. Alkalis are soluble bases; they feel soapy and can also be corrosive. Household alkalis include sodium hydroxide in drain cleaners and ammonia in cleaning fluids. Many acids and alkalis are hazardous and must be handled with care, wearing safety goggles and gloves.
酸是有酸味且具有腐蚀性的物质。常见的例子包括柠檬中的柠檬酸、醋中的醋酸以及实验室中的盐酸。碱是可溶的碱；它们感觉滑腻，也可能具有腐蚀性。家庭中的碱包括下水道清洁剂中的氢氧化钠和清洁液中的氨。许多酸和碱都具有危险性，必须小心操作，佩戴护目镜和手套。
When an acid and an alkali react together, a neutralisation reaction occurs, producing a salt and water. For example, hydrochloric acid + sodium hydroxide → sodium chloride + water. Neutralisation is used in many real-life applications, such as taking antacids to relieve indigestion or treating acidic soil with lime (calcium oxide). The concept of neutralisation is also important for understanding pH changes.
当酸和碱发生反应时，就会发生中和反应，生成盐和水。例如，盐酸 + 氢氧化钠 → 氯化钠 + 水。中和反应在许多现实应用中都有使用，如服用抗酸剂缓解消化不良，或使用石灰（氧化钙）处理酸性土壤。中和的概念对于理解 pH 值变化也至关重要。
9. Indicators and the pH Scale | 指示剂与 pH 标度
Indicators are dyes that change colour in acids and alkalis. Litmus is a common indicator that turns red in acidic solutions and blue in alkaline solutions. Universal indicator is a mixture of dyes that gives a range of colours across the pH scale, allowing us to estimate the strength of an acid or alkali. It turns red in strong acids, green in neutral solutions, and purple in strong alkalis.
指示剂是在酸和碱中会变色的染料。石蕊是一种常见的指示剂，在酸性溶液中变红，在碱性溶液中变蓝。通用指示剂是一种染料混合物，能在 pH 标度上显示一系列颜色，使我们能够估计酸或碱的强度。它在强酸中呈红色，在中性溶液中呈绿色，在强碱中呈紫色。
The pH scale runs from 0 to 14. Solutions with pH less than 7 are acidic; the lower the number, the stronger the acid. Solutions with pH greater than 7 are alkaline; the higher the number, the stronger the alkali. A pH of exactly 7 indicates a neutral substance, like pure water. The scale is logarithmic, meaning each whole pH value below 7 is ten times more acidic than the next higher value.
pH 标度范围从 0 到 14。pH 小于 7 的溶液是酸性的；数值越低，酸性越强。pH 大于 7 的溶液是碱性的；数值越高，碱性越强。pH 刚好为 7 表示中性物质，如纯水。pH 标度是对数尺度，意味着在 7 以下，每个整数值的酸性是下一个更高值的十倍。
10. Chemical Reactions of Acids | 酸的化学反应
Acids react with many metals to produce a salt and hydrogen gas. The general equation is: acid + metal → salt + hydrogen. For instance, magnesium ribbon reacts with hydrochloric acid to form magnesium chloride and hydrogen gas. The hydrogen can be tested using a burning splint, which produces a squeaky pop sound. Not all metals react with acids; copper does not react under normal conditions, while potassium reacts so vigorously it is dangerous in school labs.
酸与许多金属反应，生成盐和氢气。通式为：酸 + 金属 → 盐 + 氢气。例如，镁条与盐酸反应生成氯化镁和氢气。氢气可用燃烧的木条检验，会产生特有的“噗”声。并非所有金属都能与酸反应；铜在正常条件下不反应，而钾反应过于剧烈，在学校实验室中非常危险。
Acids also react with metal carbonates to produce a salt, water and carbon dioxide. The reaction can be represented as: acid + metal carbonate → salt + water + carbon dioxide. Marble chips (calcium carbonate) added to hydrochloric acid fizz due to the release of CO₂ gas. Carbon dioxide gas can be identified by bubbling it through limewater, which turns milky or cloudy. This reaction is used in investigating acid rain’s effect on limestone buildings.
酸还与金属碳酸盐反应，生成盐、水和二氧化碳。反应可表示为：酸 + 金属碳酸盐 → 盐 + 水 + 二氧化碳。加入盐酸的大理石碎片（碳酸钙）会因释放 CO₂ 气体而冒泡。二氧化碳气体可通过将其通入石灰水中进行鉴别，石灰水会变浑浊或呈乳白色。这个反应被用来研究酸雨对石灰岩建筑的影响。
11. Elements, Compounds and the Periodic Table | 元素、化合物与周期表
An element is a pure substance made of only one type of atom. All known elements are listed in the Periodic Table, which arranges them in order of increasing atomic number. Metals are found on the left and in the centre, while non-metals are mostly on the right. Each element has a unique chemical symbol; for example, oxygen is ‘O’, sodium is ‘Na’, and gold is ‘Au’.
元素是由仅一种类型的原子构成的纯物质。所有已知元素都列在周期表中，周期表按原子序数递增的顺序排列。金属位于左侧和中央，而非金属大多在右侧。每种元素都有独特的化学符号；例如，氧是 ‘O’，钠是 ‘Na’，金是 ‘Au’。
Compounds are formed when two or more different elements chemically combine in fixed proportions. The properties of a compound are entirely different from the elements that make it. Water (H₂O) is a compound made from hydrogen and oxygen, yet it is a liquid at room temperature while both elements are gases. A chemical formula shows the types and numbers of atoms in a compound. Mixtures, unlike compounds, can be separated by physical means because the substances are not chemically bonded.
化合物是由两种或多种不同元素以固定比例化学结合而形成的。化合物的性质与组成它的元素完全不同。水 (H₂O) 是由氢和氧组成的化合物，但它在室温下是液体，而两种元素都是气体。化学式表示化合物中原子的种类和数目。与化合物不同，混合物可以通过物理方法分离，因为其中的物质并未化学键合。
12. Combustion and the Fire Triangle | 燃烧与火三角
Combustion is a chemical reaction in which a fuel reacts with oxygen, releasing energy in the form of heat and light. For combustion to occur, three things are needed: a fuel, oxygen and heat. These three requirements are often shown as the sides of a ‘fire triangle’. Removing any one of these sides extinguishes the fire. A fire blanket cuts off oxygen, while water removes heat and, in some cases, the fuel source.
燃烧是一种化学反应，燃料与氧气反应，以热和光的形式释放能量。发生燃烧需要三样东西：燃料、氧气和热量。这三个条件通常表示为“火三角”的边。移除其中任何一边即可灭火。灭火毯切断氧气，而水可以移除热量，在某些情况下也能移除燃料源。
Complete combustion of hydrocarbons produces carbon dioxide and water. For example, methane (CH₄) + oxygen → carbon dioxide (CO₂) + water (H₂O), when balanced: CH₄ + 2O₂ → CO₂ + 2H₂O. Incomplete combustion, which happens when there is insufficient oxygen, produces carbon monoxide (CO) and carbon soot. Carbon monoxide is a toxic gas that can be fatal, so appliances must be well ventilated. Understanding combustion also links to environmental topics such as greenhouse gases and global warming.
碳氢化合物的完全燃烧生成二氧化碳和水。例如，甲烷 (CH₄) + 氧气 → 二氧化碳 (CO₂) + 水 (H₂O)，配平后为：CH₄ + 2O₂ → CO₂ + 2H₂O。当氧气供应不足时发生不完全燃烧，生成一氧化碳 (CO) 和炭黑。一氧化碳是一种有毒气体，可能致命，因此设备必须通风良好。理解燃烧也联系到温室气体和全球变暖等环境主题。
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