📚 Year 7 CIE Chemistry: Key Concepts Overview | 核心知识点梳理
Welcome to this comprehensive Year 7 CIE Chemistry revision guide. We will walk through every essential topic you need to know – from the tiniest particles to whole chemical reactions. Mastering these fundamentals now will give you the confidence and understanding required for more advanced science in the years ahead.
欢迎阅读这篇全面的 Year 7 CIE 化学复习指南。我们将一起梳理你需要掌握的每一个核心课题——从最微小的粒子到完整的化学反应。现在掌握这些基础，将为你未来的科学学习带来自信和牢固的理解。
1. States of Matter | 物质的状态
All substances can exist in one of three states: solid, liquid or gas. The state depends on how strongly the particles are held together.
所有物质都可以以三种状态之一存在：固体、液体或气体。状态取决于粒子之间结合的紧密程度。
Solids have a definite shape and a definite volume. Their particles are packed tightly in a regular pattern and can only vibrate in fixed positions.
固体有固定的形状和体积。它们的粒子紧密地排列在规则的模型中，只能在固定的位置振动。
Liquids have a fixed volume but take the shape of their container. Their particles are close together but can slide past each other, allowing the liquid to flow.
液体有固定的体积，但会随容器改变形状。它们的粒子彼此靠近，但可以相互滑动，使液体能够流动。
Gases have no fixed shape and no fixed volume. The particles are far apart and move randomly at high speed, spreading out to fill all available space.
气体没有固定的形状和体积。粒子相距很远，高速随机运动，会扩散并充满所有可用空间。
Changes of state – melting, freezing, boiling, condensing and sublimation – happen when energy is added or removed, not when the particles themselves change.
状态变化——熔化、凝固、沸腾、冷凝和升华——发生在能量增加或减少时，粒子本身并不会改变。
2. The Particle Model | 粒子模型
The particle model is a simple way to explain the behaviour of solids, liquids and gases. It states that all matter is made up of tiny particles that are constantly moving.
粒子模型是解释固体、液体和气体行为的简单方法。它指出所有物质都由不断运动的微小粒子组成。
There are empty spaces between particles, and the amount of space changes with temperature. When a substance is heated, particles gain energy and move faster, often spreading further apart.
粒子之间存在空隙，空隙的大小随温度而变化。物质受热时，粒子获得能量，运动加快，通常彼此距离增大。
This model helps us understand why solids cannot be compressed, why liquids can be poured and why gases can be squeezed into a smaller volume.
这个模型帮助我们理解为什么固体不能被压缩，液体可以倾倒，气体可以被挤压到更小的体积中。
Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration. It happens fastest in gases, more slowly in liquids and not at all in solids.
扩散是粒子从高浓度区域向低浓度区域移动的过程。扩散在气体中最快，液体中较慢，固体中几乎不发生。
3. Atoms and Elements | 原子与元素
An atom is the smallest particle of an element that still has the properties of that element. Everything you can touch is made of atoms.
原子是元素中仍具有该元素性质的最小粒子。你能触摸到的一切都由原子构成。
An element is a pure substance made of only one type of atom. There are about 100 different elements, and each has its own chemical symbol, such as H for hydrogen, O for oxygen and Fe for iron.
元素是由同一种原子组成的纯物质。大约有100种不同的元素，每种都有自己的化学符号，例如 H 代表氢，O 代表氧，Fe 代表铁。
Atoms themselves contain even smaller subatomic particles: protons and neutrons in the central nucleus, with electrons moving around the nucleus. The number of protons decides which element the atom is.
原子内部包含更小的亚原子粒子：原子核中有质子和中子，电子围绕原子核运动。质子的数目决定了原子属于哪种元素。
Elements can be classified as metals or non‑metals based on their properties. Metals are usually shiny, good conductors of heat and electricity, and can be hammered into shape. Non‑metals are often dull, poor conductors and brittle when solid.
元素可以根据性质分为金属和非金属。金属通常有光泽，是热和电的良导体，可以锤打成一定形状。非金属通常暗淡无光，导电导热性差，固体时易碎。
4. The Periodic Table | 元素周期表
The periodic table arranges all the known elements in order of increasing proton number (atomic number). It is a map that chemists use to see patterns in element properties.
元素周期表按照质子数（原子序数）递增的顺序排列所有已知元素。它是化学家用来观察元素性质规律的一张地图。
Horizontal rows are called periods; as you move across a period, the elements change from metallic to non‑metallic character. Vertical columns are called groups, and elements in the same group have similar chemical properties because they have the same number of outer‑shell electrons.
横行叫做周期；沿周期从左到右，元素的金属性逐渐减弱，非金属性增强。纵列叫做族，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。
Metals are found on the left and centre of the table, while non‑metals occupy the upper right. A zig‑zag line separates them. Hydrogen is unusual – it sits alone at the top left but is a non‑metal gas.
金属位于周期表的左侧和中部，而非金属占据右上方。一条锯齿形线将它们分开。氢很不寻常——它单独位于左上角，但是一种非金属气体。
Learning the names and symbols of the first 20 elements is essential for Year 7. For example, sodium (Na), magnesium (Mg), chlorine (Cl) and calcium (Ca) appear in many reactions.
掌握前20种元素的名称和符号对 Year 7 至关重要。例如，钠 (Na)、镁 (Mg)、氯 (Cl) 和钙 (Ca) 在许多反应中都会出现。
5. Compounds and Mixtures | 化合物与混合物
A compound is a pure substance formed when two or more different elements chemically combine. The atoms are joined by chemical bonds and cannot be separated by physical means.
化合物是由两种或以上不同元素通过化学结合形成的纯物质。原子间通过化学键结合，无法用物理方法分离。
Compounds have a fixed composition. Water (H₂O) always contains two hydrogen atoms for every oxygen atom. Their properties are often very different from the elements they are made from.
化合物有固定的组成。水 (H₂O) 总是由两个氢原子和一个氧原子构成。化合物的性质往往与组成它的元素大不相同。
A mixture contains two or more substances (elements or compounds) that are not chemically combined. Each part keeps its own properties, and the composition can vary.
混合物包含两种或以上的物质（元素或化合物），它们之间没有发生化学结合。每种成分保持自身的性质，组成比例可以变化。
Air is a mixture of gases; sea water is a mixture of water, salt and other minerals. Mixtures can usually be separated using physical techniques such as filtering or distilling.
空气是气体的混合物；海水是水、盐和其他矿物质的混合物。混合物通常可以用过滤、蒸馏等物理技术进行分离。
6. Physical and Chemical Changes | 物理变化与化学变化
A physical change alters the form or appearance of a substance but does not produce a new substance. Melting ice, cutting paper and dissolving sugar in water are all physical changes. Most physical changes are easily reversible.
物理变化改变物质的形式或外观，但不产生新物质。冰融化、剪纸、糖溶于水都是物理变化。大多数物理变化易于逆转。
A chemical change (chemical reaction) makes one or more new substances with different properties. Signs of a chemical reaction include a colour change, a temperature change, bubbles of gas appearing, or a solid (precipitate) forming.
化学变化（化学反应）生成一种或多种性质不同的新物质。化学反应的迹象包括颜色改变、温度变化、气体气泡出现或沉淀（固体）生成。
Burning a candle, rusting of iron and the reaction between vinegar and baking soda are all chemical changes. Chemical changes are often difficult or impossible to reverse.
蜡烛燃烧、铁生锈和醋与小苏打反应都是化学变化。化学变化往往很难或无法逆转。
Remember: during any change the total mass stays the same – atoms are simply rearranged, never created or destroyed. This is the law of conservation of mass.
请记住：在任何变化中，总质量保持不变——原子只是重新排列，既不会凭空产生也不会凭空消失。这就是质量守恒定律。
7. Acids and Alkalis | 酸和碱
Acids contain hydrogen and release hydrogen ions (H⁺) when dissolved in water. They taste sour and can be corrosive. Common laboratory acids are hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃).
酸含有氢，溶于水时释放氢离子 (H⁺)。酸有酸味，可能具有腐蚀性。实验室常见的酸有盐酸 (HCl)、硫酸 (H₂SO₄) 和硝酸 (HNO₃)。
Alkalis are soluble bases. They release hydroxide ions (OH⁻) in water. Alkalis feel soapy and can also be corrosive. Examples include sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH)₂).
碱是可溶的碱性物质。碱在水中释放氢氧根离子 (OH⁻)，触感滑腻，也可能具有腐蚀性。例子有氢氧化钠 (NaOH) 和氢氧化钙 (Ca(OH)₂)。
The pH scale measures how acidic or alkaline a solution is. It runs from 0 (strongly acidic) to 14 (strongly alkaline), with 7 being neutral. Universal indicator or litmus paper can be used to estimate pH.
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。可以使用通用指示剂或石蕊试纸估计 pH 值。
When an acid reacts with an alkali, they neutralise each other. The general equation is:
Acid + Alkali → Salt + Water
当酸与碱反应时，它们相互中和。一般方程式为：
酸 + 碱 → 盐 + 水
loric acid plus sodium hydroxide gives 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。
8. Simple Chemical Reactions | 简单化学反应
Many reactions in Year 7 involve acids reacting with metals or with carbonates. These reactions produce gases that can be tested.
Year 7 涉及的许多反应是酸与金属或酸与碳酸盐的反应。这些反应会产生可以检验的气体。
Acid + metal → salt + hydrogen gas. Hydrogen makes a 'squeaky pop' with a lighted splint. For instance, zinc with hydrochloric acid:
酸 + 金属 → 盐 + 氢气。氢气遇点燃的木条会发出'噗'的爆鸣声。例如锌与盐酸反应：
Zn + 2HCl → ZnCl₂ + H₂
n dioxide. Carbon dioxide turns limewater milky. For example, calcium carbonate with hydrochloric acid:
酸 + 碳酸盐 → 盐 + 水 + 二氧化碳。二氧化碳能使石灰水变浑浊。例如碳酸钙与盐酸反应：
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
Combustion (burning) is a reaction with oxygen that releases heat and light. For a hydrocarbon fuel, the products are carbon dioxide and water. Oxidation is a slower reaction, such as rusting of iron, where oxygen combines with metal over time.
燃烧是与氧气的反应，放出热和光。对于碳氢燃料，产物是二氧化碳和水。氧化是一种较慢的反应，例如铁生锈，是氧气逐渐与金属结合的过程。
Reactions can be exothermic (release energy, making surroundings hotter) or endothermic (absorb energy, making surroundings cooler). Understanding energy changes helps us control reactions safely.
反应可以是放热的（释放能量，使周围温度升高）或吸热的（吸收能量，使周围温度降低）。了解能量变化有助于我们安全地控制化学反应。
9. Separation Methods | 分离方法
Chemists use different separation techniques to split mixtures into their components. The method chosen depends on the physical properties of the substances present.
化学家使用不同的分离技术将混合物分离成各组分。选择哪种方法取决于混合物中各物质的物理性质。
Filtration separates an insoluble solid from a liquid. The mixture is poured through filter paper; the solid stays as residue while the liquid (filtrate) passes through.
过滤将不溶性固体与液体分离。将混合物倾倒通过滤纸，固体作为残渣留在滤纸上，而液体（滤液）通过。
Evaporation is used to obtain a soluble solid from a solution by heating until the liquid evaporates. For example, salt can be recovered from salt water.
蒸发用于从溶液中获得可溶性固体，通过加热使液体蒸发。例如，可以从盐水中回收食盐。
Distillation collects the liquid as well by boiling it and condensing the vapour back into a liquid. This is used when both components are liquids with different boiling points or when the liquid is needed pure.
蒸馏则通过沸腾将液体蒸发，再冷凝蒸气回收液体，从而同时保留液体。当两种组分是沸点不同的液体或需要纯净液体时使用蒸馏。
Chromatography separates mixtures of coloured soluble substances, such as inks or dyes. The different components travel at different speeds up paper or a thin layer, creating a pattern called a chromatogram.
色谱法分离可溶性有色物质的混合物，如墨水或染料。不同成分在纸上或以薄层形式以不同速度移动，形成色谱图。
A magnet can be used to separate magnetic materials, such as iron filings, from non‑magnetic materials. Sieving separates solids of different particle sizes.
磁铁可用于将铁屑等磁性材料与非磁性材料分离。过筛可以分离不同颗粒大小的固体。
10. Air, Water and Earth's Resources | 空气、水与地球资源
Air is a mixture of gases. It consists of about 78% nitrogen, 21% oxygen, and small amounts of carbon dioxide, water vapour and noble gases. Oxygen supports combustion and respiration.
空气是气体的混合物，约含 78% 的氮气、21% 的氧气，以及少量二氧化碳、水蒸气和稀有气体。氧气支持燃烧和呼吸作用。
Water is essential for life. Natural water sources contain dissolved substances and microorganisms, so water is treated before drinking. Typical treatment steps include sedimentation, filtration and chlorination to kill bacteria.
水对生命至关重要。天然水源含有溶解物质和微生物，因此水在饮用前需要处理。典型的处理步骤包括沉降、过滤和加氯消毒以杀灭细菌。
The Earth's crust provides many resources. Rocks are mixtures of minerals. Limestone is mainly calcium carbonate; it is used for building and in making cement. Ores are rocks that contain enough metal compounds to make extraction worthwhile. Metals are extracted from their ores by chemical reactions, often using carbon or electrolysis.
地壳提供了许多资源。岩石是矿物的混合物。石灰石的主要成分是碳酸钙，用于建筑和制造水泥。矿石是含有足够金属化合物、值得开采的岩石。金属通过化学反应从矿石中提取，通常使用碳或电解法。
The three main rock types are igneous (formed from cooled magma, e.g. granite), sedimentary (formed from compressed sediments, e.g. sandstone, limestone) and metamorphic (changed by heat and pressure, e.g. marble from limestone).
三大岩石类型为火成岩（岩浆冷却形成，如花岗岩）、沉积岩（沉积物压缩形成，如砂岩、石灰岩）和变质岩（受热和压力作用转化，如石灰岩变成大理岩）。
Understanding the natural cycles of water and carbon, as well as the limited nature of many resources, highlights the importance of using materials sustainably.
了解水循环和碳循环，以及许多资源的有限性，凸显了可持续利用材料的重要性。
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