OCR Year 7 Chemistry: Key Formulas & Theorems Quick Reference | 公式定理速查手册

📚 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。

Solids have particles packed 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。
Liquids have particles close together but not in a fixed pattern. 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。
Gases have particles that are far 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 / Evaporation: liquid → gas. 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。
Gas pressure is caused by particles 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。

Complete 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。
Oxidation 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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OCR Year 7 Chemistry: Key Formulas & Theorems Quick Reference | 公式定理速查手册