📚 Year 8 Cambridge Chemistry: Core Knowledge Overview | Year 8 Cambridge 化学：核心知识点梳理
Welcome to this comprehensive overview of Year 8 Cambridge Chemistry. Whether you are preparing for a test or simply building your scientific understanding, this guide walks you through the essential topics – from the tiny particles that make up all matter to the chemical reactions shaping our everyday world. Each concept is presented clearly, with examples and key facts to support your revision.
欢迎阅读这份 Year 8 Cambridge 化学核心知识梳理。无论你是在备考，还是想扎实地建立科学基础，这篇指南将带你走过从构成万物的微小粒子到日常化学反应的各个重要主题。每个概念都配以清晰的解释、示例和关键事实，帮助你的学习和复习。
1. The Particle Model of Matter | 物质的粒子模型
All matter is made of extremely small particles that are constantly moving. The way these particles are arranged determines whether a substance is a solid, a liquid or a gas.
所有物质都由不断运动的微小粒子构成。这些粒子的排列方式决定了物质是固体、液体还是气体。
In solids, particles are packed closely together in a regular pattern and can only vibrate in fixed positions. This gives solids a definite shape and volume.
在固体中，粒子紧密排列成规则的图案，只能在固定的位置上振动。因此固体有确定的形状和体积。
In liquids, particles are still close together but can slide past one another. A liquid has a fixed volume but takes the shape of its container.
液体中的粒子仍然紧密，但可以相互滑动。液体有固定的体积，但形状会随容器改变。
In gases, particles are far apart and move rapidly in all directions. Gases have no fixed shape or volume and can be compressed easily.
气体中的粒子相距很远，并朝各个方向快速运动。气体没有固定的形状和体积，且容易被压缩。
Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration. It explains how smells travel through a room.
扩散是粒子从高浓度区域向低浓度区域运动的过程。它解释了气味如何在房间中传播。
Gas pressure is caused by the collisions of gas particles with the walls of their container. The more frequent and energetic the collisions, the higher the pressure.
气体压力是由气体粒子撞击容器壁引起的。碰撞越频繁、能量越大，压力就越高。
During changes of state, such as melting or boiling, the particles themselves do not change; only their arrangement and the amount of energy they possess alter.
在状态变化（如熔化或沸腾）过程中，粒子本身不变，改变的只是它们的排列方式和所具有的能量。
2. Atoms, Elements and the Periodic Table | 原子、元素与周期表
An atom is the smallest particle of an element that can take part in a chemical reaction. Every element is made of only one type of atom.
原子是能参与化学反应的元素最小粒子。每种元素只由一种原子构成。
Atoms contain a central nucleus composed of protons and neutrons, with electrons moving around the nucleus in shells.
原子包含由质子和中子组成的中心原子核，电子在核外分层排布并运动。
An element is a pure substance that cannot be broken down into simpler substances by chemical means. Examples include oxygen, iron and gold.
元素是一种纯物质，无法通过化学方法分解成更简单的物质。例如氧、铁和金。
The Periodic Table arranges all known elements in order of increasing atomic number (the number of protons in the nucleus).
元素周期表按原子序数（即原子核内的质子数）递增的顺序排列所有已知元素。
Vertical columns are called groups. Elements in the same group have similar chemical properties because they have the same number of electrons in their outermost shell.
纵列称为族。同族元素具有相似的化学性质，因为它们最外层电子数相同。
Horizontal rows are called periods. As you move across a period, the properties of elements change gradually from metallic to non-metallic.
横行称为周期。在同一周期中，从左到右，元素性质逐渐从金属性变为非金属性。
Group 1 metals are the alkali metals, which are very reactive. Group 7 elements are the halogens, and Group 0 (or 8) consists of the unreactive noble gases.
第1族金属是碱金属，非常活泼。第7族是卤素，第0族（或第8族）是化学性质极不活泼的稀有气体。
3. Compounds and Mixtures | 化合物与混合物
A compound is a substance formed when two or more different elements are chemically bonded together. The bonds can be ionic or covalent.
化合物是两种或多种不同元素通过化学键结合形成的物质。化学键可以是离子键或共价键。
The properties of a compound are entirely different from those of the elements it contains. For example, sodium chloride is a white edible crystal, yet sodium is a reactive metal and chlorine is a poisonous gas.
化合物的性质与组成它的元素完全不同。比如氯化钠是可食用的白色晶体，而钠是活泼金属，氯是有毒气体。
A mixture is a combination of two or more substances that are not chemically joined together. The components keep their own properties.
混合物是两种或多种未发生化学结合的物质混合在一起。各组分保持原有的性质。
Mixtures can be separated by physical techniques such as filtration, distillation, chromatography and evaporation. The method used depends on the physical properties of the substances involved.
混合物可以通过过滤、蒸馏、色谱法和蒸发等物理技术进行分离。选择的方法取决于有关物质的物理性质。
Air is a homogeneous mixture of gases, mainly nitrogen and oxygen. Seawater is a mixture of water and dissolved salts.
空气是气体的均匀混合物，主要包含氮气和氧气。海水是水和溶解盐类的混合物。
4. Chemical Formulas and Equations | 化学式与方程式
A chemical formula shows the symbols of the elements present in a compound and the ratio of atoms. For example, H₂O means each water molecule contains two hydrogen atoms and one oxygen atom.
化学式表示化合物中存在的元素符号以及原子个数比。例如 H₂O 表示每个水分子含有两个氢原子和一个氧原子。
The small numbers written below the line are called subscripts. They indicate how many atoms of that element are in one unit of the compound.
写在右下角的数字称为下标，它们表示该元素在一个化合物单元中的原子数目。
eactants are written on the left and the products on the right, separated by an arrow (→).
化学方程式用符号和化学式表示化学反应。反应物写在左边，生成物写在右边，中间用箭头（→）分隔。
The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction. Therefore, the total mass of reactants must equal the total mass of products.
质量守恒定律指出，化学反应中物质不能被创造或消灭。因此反应物的总质量必须等于生成物的总质量。
e number of atoms of each element is the same on both sides. For example, 2H₂ + O₂ → 2H₂O.
为遵循这个定律，必须在化学式前加上系数使方程式配平，使得每种元素的原子个数在两边相等。例如 2H₂ + O₂ → 2H₂O。
State symbols are often added to show the physical state: (s) for solid, (l) for liquid, (g) for gas and (aq) for aqueous solution.
通常添加状态符号以表明物理状态：(s) 固体，(l) 液体，(g) 气体，(aq) 水溶液。
5. Physical and Chemical Changes | 物理变化与化学变化
A physical change alters the appearance or state of a substance but does not create a new substance. The change is usually easy to reverse.
物理变化改变物质的外观或状态，但不生成新物质。这种变化通常容易逆转。
Examples of physical changes include melting ice, boiling water, dissolving sugar in tea and breaking a glass bottle.
物理变化的例子包括冰融化、水沸腾、糖溶于茶中和打碎玻璃瓶。
A chemical change (or chemical reaction) produces one or more new substances that have different properties from the original substances. It is often difficult to reverse.
化学变化（或化学反应）生成一种或多种性质不同于原物质的新物质。这种变化通常难以逆转。
Signs that a chemical reaction has taken place include a colour change, the formation of a gas (bubbles), a change in temperature (getting hotter or colder) and the appearance of a precipitate (an insoluble solid).
化学反应的迹象包括颜色变化、气体生成（气泡）、温度变化（变热或变冷）以及沉淀（不溶固体）的出现。
Combustion, such as burning magnesium in air, is a fast chemical change that releases heat and light. The magnesium ribbon burns to form white magnesium oxide powder, a completely new substance.
燃烧，如镁在空气中燃烧，是一种快速化学变化，释放出热和光。镁带燃烧后形成白色粉末氧化镁，这是一种全新物质。
6. Acids, Bases and the pH Scale | 酸、碱与pH值
Acids are substances that release hydrogen ions (H⁺) when dissolved in water. They have a sour taste and can be corrosive.
酸是溶于水时释放氢离子 (H⁺) 的物质。它们有酸味，可能具有腐蚀性。
Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Vinegar and lemon juice contain weak organic acids.
常见的实验室酸有盐酸 (HCl)、硫酸 (H₂SO₄) 和硝酸 (HNO₃)。醋和柠檬汁含有弱有机酸。
Bases are substances that can neutralise acids. Alkalis are soluble bases that release hydroxide ions (OH⁻) in water. Examples include sodium hydroxide (NaOH) and potassium hydroxide (KOH).
碱是能中和酸的物质。可溶性碱在水中释放氢氧根离子 (OH⁻)，称为碱溶液。例子有氢氧化钠 (NaOH) 和氢氧化钾 (KOH)。
The pH scale measures how acidic or alkaline a solution is. It runs from 0 (very acidic) to 14 (very alkaline), with 7 being neutral.
pH标度用来衡量溶液的酸碱程度。范围从0（强酸性）到14（强碱性），7为中性。
Indicators, such as litmus and universal indicator, change colour depending on the pH of the solution they are added to. Litmus turns red in acid and blue in alkali.
指示剂如石蕊和通用指示剂，会根据所加入溶液的pH值改变颜色。石蕊在酸中变红，在碱中变蓝。
7. Neutralisation Reactions | 中和反应
i to produce a salt and water. The general word equation is: acid + alkali → salt + water.
中和反应是酸与碱反应生成盐和水的过程。通用文字方程式为：酸 + 碱 → 盐 + 水。
d combine with the hydroxide ions from the alkali to form water molecules: H⁺ + OH⁻ → H₂O.
酸中的氢离子与碱中的氢氧根离子结合形成水分子：H⁺ + OH⁻ → H₂O。
eacts with sodium hydroxide to produce sodium chloride and water: HCl + NaOH → NaCl + H₂O.
例如，盐酸与氢氧化钠反应生成氯化钠和水：HCl + NaOH → NaCl + H₂O。
Neutralisation has many real-world applications. Farmers add lime (calcium oxide) to acidic soil to raise its pH. Antacid tablets containing bases are used to relieve indigestion caused by excess stomach acid.
中和反应有许多实际应用。农民向酸性土壤添加石灰（氧化钙）来提高pH值。含有碱的抗酸药片可用来缓解由胃酸过多引起的消化不良。
The type of salt produced depends on the acid used. Hydrochloric acid produces chloride salts, sulfuric acid produces sulfate salts, and nitric acid produces nitrate salts.
生成的盐类型取决于所用的酸：盐酸生成氯化物盐，硫酸生成硫酸盐，硝酸生成硝酸盐。
8. Metals and Non-metals | 金属与非金属
Metals are generally shiny, conduct heat and electricity well, and can be hammered into shapes (malleable) or drawn into wires (ductile). They often have high melting and boiling points.
金属通常有光泽，是热和电的良导体，并具有延展性（可锤打成形）和韧性（可拉成丝）。它们的熔点和沸点通常较高。
Non-metals are typically dull in appearance, poor conductors of heat and electricity, and brittle when solid. Many are gases at room temperature.
非金属通常外观暗淡，是热和电的不良导体，固态时易碎。很多非金属在室温下为气体。
The reactivity series is a list of metals arranged in order of how vigorously they react. Potassium and sodium are at the very top, whereas gold and platinum are at the bottom.
金属活动性顺序是按金属反应剧烈程度排列的列表。钾和钠位于最顶端，而金和铂位于最底部。
A more reactive metal can displace a less reactive metal from its compound in a displacement reaction. For example, zinc can displace copper from copper sulfate solution.
更活泼的金属可以从化合物中把较不活泼的金属置换出来。例如锌能把铜从硫酸铜溶液中置换出来。
Alloys are mixtures of a metal with one or more other elements, usually other metals. They are designed to have improved properties – steel, an alloy of iron and carbon, is much harder than pure iron.
合金是金属与一种或多种其它元素（通常是金属）的混合物。设计合金是为了改善性能——钢是铁和碳的合金，比纯铁坚硬得多。
9. Earth Science: Rocks and Weathering | 地球科学：岩石与风化
Rocks are classified into three main types based on how they form: igneous, sedimentary and metamorphic.
根据形成方式，岩石分为三大类：火成岩、沉积岩和变质岩。
Igneous rocks form when magma or lava cools and solidifies. Granite is a common intrusive igneous rock with large crystals; basalt is an extrusive igneous rock with small crystals.
火成岩由岩浆或熔岩冷却凝固而成。花岗岩是一种常见的具有大晶体的侵入型火成岩；玄武岩是一种具有小晶体的喷出型火成岩。
Sedimentary rocks are made from layers of sediment (sand, mud, remains of organisms) that have been compacted and cemented over millions of years. Limestone and sandstone are common examples; they often contain fossils.
沉积岩是由沉积物（沙、泥、生物遗骸）层经过数百万年的压紧和胶结作用形成的。石灰岩和砂岩是常见的例子，沉积岩中常含有化石。
Metamorphic rocks are formed when existing igneous or sedimentary rocks are changed by extreme heat and pressure. Marble is formed from limestone, and slate from shale.
变质岩是原有的火成岩或沉积岩在极端高温和高压下发生变质而形成的。大理石由石灰岩变质而来，板岩由页岩变质而来。
Weathering is the breakdown of rocks in place at the Earth's surface. Physical weathering includes freeze-thaw action, where water seeps into cracks, freezes and expands, breaking the rock apart.
风化是地表岩石在原地的分解。物理风化包括冻融作用，水渗入裂缝、冻结膨胀，使岩石破裂。
Chemical weathering involves chemical reactions that dissolve or alter minerals. For example, acid rain, which contains weak carbonic acid or sulfuric acid, can dissolve limestone and damage stone buildings.
化学风化涉及溶解或改变矿物质的化学反应。例如酸雨含有弱碳酸或硫酸，能溶解石灰岩并损坏石质建筑。
10. Chemical Reactions in Everyday Life | 日常生活中的化学反应
Many processes we rely on every day are chemical reactions. Cooking food, burning fuels, and the rusting of iron are all examples of chemical changes.
我们每天依赖的许多过程都是化学反应。烹饪食物、燃烧燃料和铁生锈都是化学变化的例子。
Oxidation is a reaction in which a substance gains oxygen. Rusting is the slow oxidation of iron in the presence of oxygen and water, forming hydrated iron(III) oxide (Fe₂O₃·xH₂O).
氧化是物质得到氧的反应。生锈是铁在有氧和水的条件下缓慢氧化，生成水合氧化铁(III) (Fe₂O₃·xH₂O)。
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