📚 Year 7 OCR Chemistry: Key Vocabulary and Terminology Memorisation Guide | Year 7 OCR 化学：关键词汇与术语速记指南
Mastering the core vocabulary is the first step to excelling in Year 7 OCR Chemistry. This guide presents essential terms organised by topic, with clear definitions in English and Chinese, plus memory tips. Use it to build a solid foundation for all future chemistry learning.
掌握核心词汇是学好 Year 7 OCR 化学的第一步。本指南按主题整理了必学术语，提供清晰的中英双语定义和记忆技巧，助你为后续化学学习打下坚实基础。
1. States of Matter and Changes of State | 物质的状态与变化
Solid: A state of matter that has a definite shape and a definite volume. The particles are packed closely together in a regular arrangement and can only vibrate in their fixed positions.
固体：具有确定形状和确定体积的物质状态。粒子紧密排列成规则结构，只能在固定位置振动。
Liquid: A state of matter that has a fixed volume but takes the shape of the bottom of its container. Particles are close together but can move past each other, so the liquid can flow.
液体：体积固定但形状随容器底部变化的物质状态。粒子彼此靠近但能相对滑动，因此液体可以流动。
Gas: A state of matter that has no fixed shape or volume. Gas particles are far apart and move quickly in all directions, completely filling any container.
气体：没有固定形状和体积的物质状态。气体粒子相距很远，快速向各个方向运动，完全充满整个容器。
Melting: The change from solid to liquid when heat energy is supplied. It occurs at the melting point.
熔化（融化）：固体吸收热量转变成液体的过程，发生在熔点温度。
Freezing: The change from liquid to solid when heat energy is removed. It occurs at the freezing point, which is the same temperature as the melting point for a pure substance.
凝固：液体放出热量转变成固体的过程，发生在凝固点。对于纯物质，凝固点与熔点相同。
Boiling / Evaporating: Boiling is the rapid change from liquid to gas throughout the liquid at the boiling point. Evaporation is the slow change from liquid to gas only at the surface, occurring at any temperature below the boiling point.
沸腾与蒸发：沸腾是液体在沸点温度整体迅速转变为气体的过程；蒸发是液体仅在表面缓慢转变为气体的过程，可在低于沸点的任何温度下发生。
Condensing: The change from gas to liquid when gas is cooled or compressed. It is the reverse of boiling or evaporation.
凝结（冷凝）：气体冷却或受压时转变为液体的过程，是沸腾或蒸发的逆过程。
Sublimation: The change directly from solid to gas without passing through the liquid state, e.g. solid carbon dioxide (dry ice) turning into carbon dioxide gas.
升华：固体不经过液态直接转变为气体的过程，如干冰（固态二氧化碳）直接变成二氧化碳气体。
2. Particle Theory and Diffusion | 微粒理论与扩散
Particle theory: All matter is made up of tiny particles that are constantly moving. There are spaces between the particles, and the particles attract each other. The higher the temperature, the faster the particles move.
微粒理论：所有物质都由微小的粒子组成，粒子在永不停息地运动。粒子之间有间隔，且粒子之间存在相互吸引力。温度越高，粒子运动越快。
Diffusion: The net movement of particles from a region of higher concentration to a region of lower concentration until they are evenly spread. Diffusion happens in liquids and gases but is fastest in gases because particles move most freely.
扩散：粒子从浓度较高的区域向浓度较低的区域净运动，直到均匀分布。扩散在液体和气体中都能发生，但在气体中最快，因为气体粒子的运动最自由。
Gas pressure: Caused by gas particles colliding with the walls of their container. Increasing the temperature or decreasing the volume increases the number and force of collisions, raising the pressure.
气体压强：由气体粒子撞击容器壁产生。升高温度或减小体积会增加碰撞次数和撞击力，从而使压强增大。
3. Elements, Compounds and Mixtures | 元素、化合物与混合物
Element: A pure substance made up of only one type of atom. Elements cannot be broken down into simpler substances by chemical means. Examples: oxygen (O₂), iron (Fe), gold (Au).
元素：仅由一种原子组成的纯净物。元素不能通过化学方法被分解成更简单的物质。例如：氧气（O₂）、铁（Fe）、金（Au）。
Compound: A pure substance made of two or more different types of atoms chemically combined in a fixed ratio. Compounds can be separated into their elements only by chemical reactions. Examples: water (H₂O), carbon dioxide (CO₂), sodium chloride (NaCl).
化合物：由两种或多种不同原子以固定比例通过化学键结合而成的纯净物。化合物只能通过化学反应分解成组成它的元素。例如：水（H₂O）、二氧化碳（CO₂）、氯化钠（NaCl）。
Mixture: Two or more substances (elements or compounds) that are physically mixed but not chemically combined. Each substance keeps its own properties, and mixtures can be separated by physical methods. Examples: air, sea water, soil.
混合物：两种或多种物质（元素或化合物）简单地混合在一起，没有发生化学结合。各组分保持其原有性质，混合物可通过物理方法分离。例如：空气、海水、泥土。
4. Atoms and Molecules | 原子与分子
Atom: The smallest particle of an element that can still take part in chemical reactions. Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons.
原子：元素能参与化学反应的最小粒子。原子由含质子和中子的原子核以及核外电子构成。
Molecule: A group of two or more atoms held together by chemical bonds. Molecules can be elements (e.g. O₂, N₂) or compounds (e.g. H₂O, CO₂).
分子：两个或更多原子通过化学键结合在一起的粒子。分子可以是单质分子（如 O₂、N₂）或化合物分子（如 H₂O、CO₂）。
Ion: A charged particle formed when an atom or a group of atoms gains or loses electrons. Positive ions (cations) form by losing electrons, negative ions (anions) form by gaining electrons, e.g. Na⁺, Cl⁻.
离子：原子或原子团得到或失去电子后形成的带电粒子。失去电子形成阳离子（如 Na⁺），得到电子形成阴离子（如 Cl⁻）。
5. Chemical Symbols and Formulae | 化学符号与化学式
Chemical symbol: A one- or two-letter abbreviation for an element. The first letter is always capitalised, and the second letter (if present) is lower case. For example, C for carbon, O for oxygen, Na for sodium.
化学符号：用一或两个字母表示元素的缩写。第一个字母始终大写，第二个字母必须小写。例如：碳 C、氧 O、钠 Na。
| English name | Symbol | 中文 |
|---|---|---|
| Hydrogen | H | 氢 |
| Carbon | C | 碳 |
| Nitrogen | N | 氮 |
| Oxygen | O | 氧 |
| Sodium | Na | 钠 |
| Magnesium | Mg | 镁 |
| Aluminium | Al | 铝 |
| Silicon | Si | 硅 |
| Sulfur | S | 硫 |
| Chlorine | Cl | 氯 |
| Potassium | K | 钾 |
| Calcium | Ca | 钙 |
| Iron | Fe | 铁 |
| Copper | Cu | 铜 |
| Zinc | Zn | 锌 |
Chemical formula: A combination of symbols and subscript numbers that shows the types and numbers of atoms in a substance. For example, H₂O means two hydrogen atoms and one oxygen atom; NaCl means one sodium ion and one chloride ion in a 1:1 ratio.
化学式：用元素符号和下标数字表示物质中各原子种类和数目的式子。例如 H₂O 表示含有两个氢原子和一个氧原子；NaCl 表示钠离子与氯离子的个数比为 1:1。
6. Introduction to Chemical Reactions | 化学反应简介
Chemical reaction: A process in which one or more substances (reactants) are changed into one or more new substances (products). Chemical reactions involve the rearrangement of atoms and are usually difficult to reverse.
化学反应：一种或多种物质（反应物）转变成一种或多种新物质（生成物）的过程。化学反应涉及原子的重新排列，通常难以逆转。
Reactant: A starting substance that is used up during a chemical reaction.
反应物：在化学反应中参加反应并被消耗的起始物质。
Product: A new substance formed during a chemical reaction.
生成物（产物）：在化学反应中生成了的新物质。
Word equation: reactants and products, linked by an arrow. Example: magnesium + oxygen → magnesium oxide.
文字表达式：用反应物和生成物的名称以及箭头来简单描述反应的方法。例：镁 + 氧气 → 氧化镁。
Symbol equation: that the number of each type of atom is the same on both sides. Example: 2Mg + O₂ → 2MgO.
化学方程式：用化学符号和化学式表示化学反应的式子。必须配平，使两边每种原子的数目相等。例：2Mg + O₂ → 2MgO。
2Mg + O₂ → 2MgO
Physical change: A change where no new substances are formed. The substance may change its state or shape, but its chemical identity remains the same. Examples: melting ice, dissolving sugar in water.
物理变化：没有新物质生成的变化。物质可能改变状态或形状，但其化学组成不变。例如：冰融化、糖溶解于水。
7. Acids, Alkalis and the pH Scale | 酸、碱与 pH 标度
Acid: A substance that has a pH less than 7 and releases hydrogen ions (H⁺) when dissolved in water. Acids taste sour and can be corrosive. Examples: hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃).
酸：pH 小于 7 并能溶于水释放出氢离子（H⁺）的物质。酸有酸味，可能具有腐蚀性。例如：盐酸（HCl）、硫酸（H₂SO₄）、硝酸（HNO₃）。
Alkali: A soluble base that has a pH greater than 7 and releases hydroxide ions (OH⁻) in water. Alkalis feel soapy and can also be corrosive. Examples: sodium hydroxide (NaOH), potassium hydroxide (KOH).
碱（可溶性碱）：pH 大于 7 并能溶于水释放出氢氧根
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