📚 OCR Year 7 Chemistry: Key Formulas & Theorems Quick Reference | 公式定理速查手册
Welcome to your go-to guide for the essential chemistry formulas, laws, and principles covered in OCR Year 7. Whether you are revising states of matter, preparing for a test on acids and alkalis, or simply brushing up on particle theory, this handbook gives you everything you need in one clear, bilingual resource.
欢迎使用这本专为 OCR Year 7 编写的化学核心公式、定律与原理速查手册。无论你是在复习物质的状态、准备关于酸和碱的测验，还是想快速回顾粒子理论，这本中英双语资源都能帮你把关键点一网打尽。
1. The Particle Model of Matter | 物质的粒子模型
All substances are made of tiny moving particles. The arrangement and motion of these particles explain the three states of matter: solid, liquid, and gas.
所有物质都由不断运动的微小粒子构成。粒子的排列方式和运动状态可以解释物质的三态：固态、液态和气态。
- d tightly in a regular pattern. They vibrate in fixed positions. → Fixed shape and volume.
- 固体的粒子紧密排列成规则结构，只能在固定位置振动。→ 形状和体积固定。
- ttern. They can slide past each other. → Fixed volume but take the shape of the container.
- 液体的粒子间距小但排列不规则，能相互滑动。→ 体积固定但形状随容器改变。
- r apart and move rapidly in all directions. → No fixed shape or volume; can be compressed.
- 气体的粒子相距很远，快速向各个方向运动。→ 没有固定的形状和体积；可被压缩。
2. Changes of State and Fixed Points | 物态变化与固定点
Changes of state are physical changes, not chemical ones. Mass is conserved when a substance changes state. At the melting point and boiling point, the temperature stays constant until the change is complete.
物态变化属于物理变化，不产生新物质。物质在状态变化过程中质量守恒。在熔点和沸点，温度保持恒定，直到状态变化完全结束。
- Melting: solid → liquid at the melting point.
- 熔化：在熔点温度下，固态 → 液态。
- Freezing: liquid → solid at the freezing point (same temperature as melting point).
- 凝固：在凝固点（与熔点温度相同）液态 → 固态。
- Boiling occurs at the boiling point throughout the liquid; evaporation occurs only at the surface.
- 沸腾 / 蒸发：液态 → 气态。沸腾在沸点温度下整个液体内部都发生；蒸发仅在液体表面发生。
- Condensation: gas → liquid. Occurs when gas cools below its boiling point.
- 冷凝：气态 → 液态。当气体冷却到沸点以下时发生。
- Sublimation: solid → gas directly (e.g., dry ice).
- 升华：直接从固态变为气态（如干冰）。
mass (before change) = mass (after change)
3. Diffusion and Gas Pressure | 扩散与气体压强
Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration. It happens in liquids and gases but is fastest in gases.
扩散是粒子从高浓度区域向低浓度区域的自发运动。扩散在液体和气体中都能发生，但在气体中最快。
- Lighter particles diffuse faster than heavier particles at the same temperature.
- 在相同温度下，较轻的粒子比较重的粒子扩散得更快。
- colliding with the walls of their container. More collisions per second → higher pressure.
- 气体压强是由粒子撞击容器壁产生的。单位时间内碰撞次数越多 → 压强越高。
- Increasing temperature increases particle speed, leading to more frequent and harder collisions, so pressure increases (if volume is fixed).
- 温度升高使粒子运动加快，碰撞更频繁、更有力，因此压强增大（若体积固定）。
4. Element, Compound, and Mixture | 单质、化合物与混合物
An element contains only one type of atom. A compound contains two or more different types of atoms chemically bonded together. A mixture contains two or more substances not chemically joined.
单质只含有一种原子。化合物由两种或多种不同种类的原子通过化学键结合而成。混合物由两种或多种物质组成，它们之间没有发生化学结合。
- Elements are listed on the Periodic Table (about 118 known).
- 单质列在元素周期表中（目前已发现约 118 种）。
- Compounds have fixed proportions of elements (e.g., H₂O always has 2 hydrogen atoms for every 1 oxygen atom).
- 化合物中各元素有固定的比例（如 H₂O 中，总是 2 个氢原子对 1 个氧原子）。
- Mixtures can be separated by physical methods such as filtration, distillation, and chromatography.
- 混合物可以通过过滤、蒸馏、层析等物理方法分离。
5. Atomic Structure Basics | 原子结构基础
Atoms are the smallest part of an element that can still be recognised as that element. They consist of a central nucleus containing protons and neutrons, with electrons orbiting in shells.
原子是单质中能独立存在并保持其化学性质的最小微粒。原子由中心的原子核（含质子和中子）和核外按电子层排布的电子组成。
| Particle / 粒子 | Relative charge / 相对电荷 | Relative mass / 相对质量 |
| Proton / 质子 | +1 | 1 |
| Neutron / 中子 | 0 | 1 |
| Electron / 电子 | –1 | ~0 (1/1840) |
- Atomic number = number of protons (defines the element).
- 原子序数 = 质子数（决定了元素种类）。
- Mass number = protons + neutrons.
- 质量数 = 质子数 + 中子数。
- In a neutral atom: number of electrons = number of protons.
- 中性原子中：电子数 = 质子数。
mass number (A) = protons (Z) + neutrons
6. The Periodic Table for Year 7 | 七年级必学元素周期表结构
The Periodic Table arranges all known elements in order of increasing atomic number. Vertical columns are called groups; horizontal rows are called periods.
元素周期表按原子序数递增的顺序排列所有已知元素。纵列称为族，横行称为周期。
- Group number tells us the number of electrons in the outer shell for main-group elements.
- 主族元素的族号等于其最外层电子数。
- Period number tells us the number of occupied electron shells.
- 周期号等于该原子所具有的电子层数。
- Metals are on the left and centre; non-metals are on the right. A stepped line separates them.
- 金属位于表的左方和中部；非金属位于右方。两者之间有一条锯齿形分界线。
- Group 1: Alkali metals (very reactive, soft). Group 7: Halogens (reactive non-metals). Group 0/8: Noble gases (unreactive).
- 第一族：碱金属（非常活泼，质地软）。第七族：卤素（活泼的非金属）。第零/第八族：稀有气体（极不活泼）。
7. Chemical Word Equations | 化学反应文字方程式
A chemical reaction forms new substances. A word equation shows the names of reactants (on the left) and products (on the right), separated by an arrow.
化学反应生成新的物质。文字方程式用反应物（左侧）和生成物（右侧）的名称表示，中间用箭头隔开。
reactant A + reactant B → product C + product D
- Common Year 7 examples:
- 七年级常见示例：
- Magnesium + Oxygen → Magnesium oxide
- 镁 + 氧气 → 氧化镁
- Hydrogen + Oxygen → Water
- 氢气 + 氧气 → 水
- Calcium carbonate + Hydrochloric acid → Calcium chloride + Water + Carbon dioxide
- 碳酸钙 + 盐酸 → 氯化钙 + 水 + 二氧化碳
- Sodium + Water → Sodium hydroxide + Hydrogen
- 钠 + 水 → 氢氧化钠 + 氢气
8. Law of Conservation of Mass | 质量守恒定律
In a chemical reaction, the total mass of the reactants equals the total mass of the products. Atoms are rearranged, not created or destroyed.
在化学反应中，反应物的总质量等于生成物的总质量。原子只是重新组合，既不会凭空产生，也不会凭空消失。
- This is why chemical equations must be balanced. The number of each type of atom is the same on both sides.
- 这就是为什么化学方程式必须配平。每种原子的数目在反应前后保持不变。
- In open systems, gas may escape, so measured mass might seem to decrease, but total mass is still conserved if you include the gas.
- 在开放体系中，气体可能逸散，导致测得的质量看似减少，但如果计入气体，总质量仍然守恒。
9. Acids and Alkalis – The pH Scale | 酸和碱 – pH 量表
The pH scale shows how acidic or alkaline a solution is. It runs from 0 to 14. Acids have a pH less than 7; alkalis have a pH greater than 7; neutral solutions have pH 7.
pH 量表用来表示溶液的酸碱度，范围从 0 到 14。酸的 pH 值小于 7；碱的 pH 值大于 7；中性溶液的 pH 等于 7。
- Indicators: Litmus (red in acid, blue in alkali), Universal indicator (rainbow colours from pH 0 to 14).
- 指示剂：石蕊试纸（酸中变红，碱中变蓝），通用指示剂（从 pH 0 到 14 显示彩虹色）。
- Neutralisation reaction: acid + alkali → salt + water
- 中和反应：酸 + 碱 → 盐 + 水
- Example: Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water
- 实例：盐酸 + 氢氧化钠 → 氯化钠 + 水
acid + alkali → salt + water
10. Combustion and Oxidation | 燃烧与氧化
Combustion is a rapid chemical reaction between a fuel and oxygen, releasing heat and light. Oxidation is a more general term for a substance gaining oxygen.
燃烧是燃料与氧气之间发生的快速化学反应，放出热和光。氧化则是一个更广泛的概念，指物质获得氧的过程。
- lete combustion of a hydrocarbon: Fuel + excess oxygen → Carbon dioxide + Water (+ energy)
- 碳氢化合物的完全燃烧：燃料 + 充足的氧气 → 二氧化碳 + 水（+ 能量）
- E.g. Methane + Oxygen → Carbon dioxide + Water
- 如：甲烷 + 氧气 → 二氧化碳 + 水
- Fire triangle: fuel, heat, oxygen. Remove any one to extinguish a fire.
- 燃烧三要素：可燃物、热量、氧气。去除任意一个要素即可灭火。
- tion of metals: metal + oxygen → metal oxide (e.g., iron + oxygen → iron oxide → rusting).
- 金属的氧化：金属 + 氧气 → 金属氧化物（如：铁 + 氧气 → 氧化铁 → 生锈）。
11. Air Composition and Separation | 空气的成分与分离
Air is a mixture of gases. Dry air contains roughly 78% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide, and trace amounts of other gases.
空气是多种气体的混合物。干空气大约含有 78% 的氮气、21% 的氧气、0.9% 的氩气、0.04% 的二氧化碳以及微量其他气体。
- Oxygen can be tested with a glowing splint – it relights.
- 氧气可用带火星的木条检验——木条复燃。
- Carbon dioxide turns limewater milky (cloudy).
- 二氧化碳能使澄清石灰水变浑浊。
- Fractional distillation of liquid air separates gases based on their different boiling points.
- 通过液态空气的分馏，可根据气体沸点不同将它们分离。
12. Key Vocabulary and Symbols | 核心词汇与符号
Familiarity with chemical symbols and state symbols helps you read and write equations confidently. Here is a quick reference table:
熟悉化学符号和状态符号能帮助你自信地阅读和书写方程式。以下是快速参考表：
| Common Chemical Symbols | 常用化学符号 |
| O – Oxygen, H – Hydrogen, C – Carbon, N – Nitrogen, Fe – Iron, Cu – Copper, Na – Sodium, Cl – Chlorine, Mg – Magnesium, Ca – Calcium | O – 氧，H – 氢，C – 碳，N – 氮，Fe – 铁，Cu – 铜，Na – 钠，Cl – 氯，Mg – 镁，Ca – 钙 |
| State symbols | 状态符号 |
| (s) – solid, (l) – liquid, (g) – gas, (aq) – aqueous (dissolved in water) | (s) – 固态, (l) – 液态, (g) – 气态, (aq) – 水溶液 |
Use these symbols to write formula equations, e.g.: 2Mg(s) + O₂(g) → 2MgO(s).
使用这些符号可以书写化学方程式，例如：2Mg(s) + O₂(g) → 2MgO(s)。
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