📚 Year 8 OCR Chemistry Formula & Theorem Quick Reference Handbook | 八年级 OCR 化学公式定理速查手册
This quick reference handbook summarises all the essential formulae, laws and key concepts you need to master in Year 8 OCR Chemistry. Keep it close for revision and use it as a checkpoint before every test. From atomic structure to gas tests, every rule is explained clearly and paired with practical examples to build your confidence.
这本速查手册汇总了八年级 OCR 化学课程中必须掌握的全部核心公式、定理与重要概念。复习时随身携带，每次考试前用它来查漏补缺。从原子结构到气体的检验，每一条规则都解释得清楚明了，并配有实例，帮助你建立信心。
1. Atomic Structure | 原子结构
Atoms are the smallest particles of an element. Each atom consists of a central nucleus containing protons and neutrons, surrounded by electrons arranged in shells. Protons carry a positive charge (+1), electrons carry a negative charge (–1), and neutrons have no charge.
原子是元素的最小微粒。每个原子都有一个含质子和中子的原子核，核外有分层排布的电子。质子带一个单位正电荷 (+1)，电子带一个单位负电荷 (–1)，中子不带电。
The number of protons in the nucleus is called the atomic number (Z) and defines the identity of the element. The mass number (A) is the total number of protons plus neutrons in the nucleus. The number of neutrons = A – Z.
原子核内质子的数目称为原子序数 (Z)，它决定了元素的种类。质量数 (A) 是原子核中质子与中子数量之和。中子数 = A – Z。
Atomic number (Z) = number of protons
Mass number (A) = number of protons + number of neutrons
原子序数 (Z) = 质子数
质量数 (A) = 质子数 + 中子数
In a neutral atom, the number of electrons equals the number of protons. Electrons fill shells in a 2, 8, 8 pattern for the first 20 elements.
在电中性的原子中，电子数等于质子数。对于前 20 号元素，电子按 2、8、8 的规律填入电子层。
2. Elements, Compounds, and Mixtures | 元素、化合物与混合物
An element is a pure substance made of only one type of atom. A compound is a pure substance formed when two or more different elements are chemically bonded together in a fixed ratio. A mixture consists of two or more substances not chemically combined, which can be separated by physical means.
元素是由同一种原子组成的纯净物。化合物是由两种或两种以上不同元素通过化学键按固定比例结合形成的纯净物。混合物由两种或多种未发生化学结合的物质组成，可通过物理方法分离。
The properties of a compound are entirely different from the elements that make it. For instance, sodium is a reactive metal, chlorine is a poisonous gas, but sodium chloride is harmless table salt.
化合物的性质与组成它的各元素完全不同。例如，钠是一种活泼金属，氯是有毒气体，但氯化钠却是无毒的食盐。
Common separation techniques for mixtures include filtration, evaporation, simple distillation, and chromatography.
常见的混合物分离方法有过滤、蒸发、简单蒸馏和色谱法。
3. The Periodic Table | 元素周期表
The Periodic Table arranges all known elements in order of increasing atomic number. Vertical columns are called groups; elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell.
元素周期表按照原子序数递增的顺序排列所有已知元素。纵列称为族；同一族的元素因最外层电子数相同而具有相似的化学性质。
Horizontal rows are called periods. As you move across a period, the atomic number increases by one, and the properties gradually change from metallic to non‑metallic.
横排称为周期。从左到右，原子序数依次增加 1，元素性质从金属性逐渐过渡到非金属性。
Group 1: alkali metals – very reactive, soft, one electron in outer shell. Group 7: halogens – reactive non‑metals, seven electrons in outer shell. Group 0: noble gases – unreactive, full outer shell.
第 1 族：碱金属——非常活泼，质地软，最外层有 1 个电子。第 7 族：卤素——活泼非金属，最外层有 7 个电子。第 0 族：稀有气体——极不活泼，最外层已满。
4. Chemical Formulae and Valency | 化学式与化合价
A chemical formula uses element symbols and subscript numbers to show the type and number of atoms in a compound. The valency (combining power) of an element tells you how many bonds an atom of that element can form.
化学式用元素符号和下标数字来表示化合物中原子的种类和数目。化合价（结合能力）表示一个原子可以形成多少个化学键。
Common valencies: hydrogen (H) = 1; oxygen (O) = 2; sodium (Na) = 1; magnesium (Mg) = 2; aluminium (Al) = 3; chlorine (Cl) = 1; carbonate (CO₃) = 2; hydroxide (OH) = 1.
常见化合价：氢 (H) = 1；氧 (O) = 2；钠 (Na) = 1；镁 (Mg) = 2；铝 (Al) = 3；氯 (Cl) = 1；碳酸根 (CO₃) = 2；氢氧根 (OH) = 1。
To write a formula, swap and drop the valency numbers. For example, aluminium oxide: Al³⁺ and O²⁻ give Al₂O₃. Magnesium chloride: Mg²⁺ and Cl⁻ give MgCl₂.
书写化学式时，将化合价的数值交叉作为下标。例如，氧化铝：Al³⁺ 和 O²⁻ → Al₂O₃。氯化镁：Mg²⁺ 和 Cl⁻ → MgCl₂。
5. Writing Chemical Equations | 书写化学方程式
A word equation describes a reaction using the names of reactants and products. A symbol equation uses chemical symbols and formulae and must be balanced so that there is the same number of each type of atom on both sides of the arrow.
文字表达式用反应物和生成物的名称描述化学反应。符号方程式使用化学符号和化学式，必须配平，使得箭头两边每种原子的数目相等。
State symbols show the physical state: (s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous (dissolved in water).
状态符号表示物质的物理状态：(s) 固态，(l) 液态，(g) 气态，(aq) 水溶液（溶于水）。
Example: Hydrogen + Oxygen → Water. Balanced symbol equation: 2H₂(g) + O₂(g) → 2H₂O(l).
示例：氢气 + 氧气 → 水。配平的符号方程式：2H₂(g) + O₂(g) → 2H₂O(l)。
Balancing rules: change only the coefficients (big numbers) in front of formulae; never alter the chemical formulae themselves.
配平原则：只改变化学式前的系数（大数字），绝不能改动化学式本身。
6. Law of Conservation of Mass | 质量守恒定律
In a chemical reaction, atoms are rearranged but no atoms are created or destroyed. The total mass of the reactants equals the total mass of the products.
在化学反应中，原子重新组合，但原子既不能被创造也不能被消灭。反应物的总质量等于生成物的总质量。
If the mass appears to change in open systems, it is because a gas enters or escapes. The law still holds when all reactants and products are accounted for.
若在开放系统中质量看似发生变化，那是因为有气体进入或逸出。考虑到所有反应物和生成物时，定律依然成立。
This law is the basis for balancing equations and for understanding why precipitation and gas‑evolution reactions show no net mass change in a sealed container.
该定律是化学方程式配平的基础，也解释了为何在密闭容器中沉淀反应或气体生成反应总质量不变。
7. Types of Chemical Reactions | 化学反应类型
Combustion: A substance reacts with oxygen, releasing heat and light. Hydrocarbons burn in excess oxygen to form carbon dioxide and water. Example: CH₄ + 2O₂ → CO₂ + 2H₂O.
燃烧：物质与氧气发生反应，放出热和光。碳氢化合物在充足氧气中燃烧生成二氧化碳和水。示例：CH₄ + 2O₂ → CO₂ + 2H₂O。
Thermal decomposition: A single compound breaks down into two or more simpler substances when heated. Example: Calcium carbonate decomposes to calcium oxide and carbon dioxide. CaCO₃(s) → CaO(s) + CO₂(g).
热分解：一种化合物在加热时分解为两种或多种较简单的物质。示例：碳酸钙分解为氧化钙和二氧化碳。CaCO₃(s) → CaO(s) + CO₂(g)。
Displacement: A more reactive element takes the place of a less reactive element in a compound. Example: Zinc + Copper sulfate → Zinc sulfate + Copper. Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s).
置换：较活泼的元素把较不活泼的元素从它的化合物中替换出来。示例：锌 + 硫酸铜 → 硫酸锌 + 铜。Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)。
Oxidation and reduction (redox): Oxidation is gain of oxygen; reduction is loss of oxygen. A reaction where one substance gains oxygen while another loses oxygen is a redox reaction.
氧化与还原（氧化还原）：氧化是获得氧，还原是失去氧。一个物质获得氧而另一个物质失去氧的反应就是氧化还原反应。
8. Acids and Alkalis | 酸与碱
An acid is a substance that produces hydrogen ions (H⁺) when dissolved in water. Common laboratory acids: hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃).
酸是溶于水时产生氢离子 (H⁺) 的物质。实验室常见酸：盐酸 (HCl)、硫酸 (H₂SO₄)、硝酸 (HNO₃)。
An alkali is a soluble base that produces hydroxide ions (OH⁻) in water. Common alkalis: sodium hydroxide (NaOH), potassium hydroxide (KOH).
碱是溶于水时产生氢氧根离子 (OH⁻) 的可溶性碱。常见碱：氢氧化钠 (NaOH)、氢氧化钾 (KOH)。
Acids have a sour taste (do not taste them!) and turn blue litmus red. Alkalis feel soapy and turn red litmus blue. Concentrated acids and alkalis are corrosive.
酸有酸味（不可品尝！），可使蓝色石蕊试纸变红。碱有滑腻感，可使红色石蕊试纸变蓝。浓酸和浓碱具有腐蚀性。
9. pH Scale and Indicators | pH 值与指示剂
The pH scale measures how acidic or alkaline a solution is. It ranges from 0 to 14. pH 7 is neutral. Values below 7 are acidic; values above 7 are alkaline. The lower the pH, the stronger the acid; the higher the pH, the stronger the alkali.
pH 值量表用于衡量溶液的酸碱度，范围从 0 到 14。pH 7 为中性；小于 7 为酸性；大于 7 为碱性。pH 越低酸性越强；pH 越高碱性越强。
Universal indicator gives a range of colours from red (strong acid) through green (neutral) to violet (strong alkali). Litmus shows only red or blue.
通用指示剂能显示一系列颜色变化：强酸为红色，中性为绿色，强碱为紫色。石蕊只显示红或蓝。
Each change of one pH unit represents a ten‑fold change in hydrogen ion concentration. For example, pH 3 is ten times more acidic than pH 4.
pH 值每变化 1 个单位，氢离子浓度就相差 10 倍。例如，pH 3 的酸性是 pH 4 的 10 倍。
10. Neutralisation | 中和反应
Neutralisation is the reaction between an acid and an alkali to form a salt and water. The ionic equation for neutralisation: H⁺(aq) + OH⁻(aq) → H₂O(l).
中和反应是酸与碱作用生成盐和水的反应。中和反应的离子方程式：H⁺(aq) + OH⁻(aq) → H₂O(l)。
Example: Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water. HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l).
示例：盐酸 + 氢氧化钠 → 氯化钠 + 水。HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)。
When naming the salt, the first part comes from the metal in the alkali, and the second part from the acid. Hydrochloric acid gives chlorides, sulfuric acid gives sulfates, nitric acid gives nitrates.
给盐命名时，前半部分来自碱中的金属，后半部分来自酸。盐酸生成氯化物，硫酸生成硫酸盐，硝酸生成硝酸盐。
Farmers use neutralisation to treat acidic soils with lime (calcium oxide or calcium hydroxide). Indigestion tablets contain bases to neutralise excess stomach acid.
农民用石灰（氧化钙或氢氧化钙）中和酸性土壤。抗胃酸片含有碱，用于中和过多的胃酸。
11. Reactions of Metals with Acids | 金属与酸的反应
Many metals react with dilute acids to produce a salt and hydrogen gas. The more reactive the metal, the faster the reaction. General word equation: Metal + Acid → Salt + Hydrogen.
许多金属能与稀酸反应生成盐和氢气。金属越活泼，反应越快。通用文字表达式：金属 + 酸 → 盐 + 氢气。
Example: Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen. Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g).
示例：镁 + 盐酸 → 氯化镁 + 氢气。Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)。
The reactivity series lists metals in order of reactivity: potassium (most reactive), sodium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold (least reactive). Metals below hydrogen in the series do not react with acids.
金属活动性顺序按活泼程度排列：钾（最活泼）、钠、钙、镁、铝、锌、铁、铜、银、金（最不活泼）。在顺序中排在氢之后的金属不能与酸反应。
The squeaky‑pop test is used to confirm the presence of hydrogen gas: a lighted splint held over the mouth of the test tube produces a squeaky pop sound.
氢气可用爆鸣实验检验：将燃着的木条移近试管口，会听到“噗”的一声轻响。
12. Testing for Common Gases | 常见气体检验
| Gas 气体 | Test 检测方法 | Positive Result 正反应结果 |
|---|---|---|
| Hydrogen (H₂) | Hold a lighted splint at the open end of the test tube. | Burns rapidly with a squeaky pop sound. |
| Oxygen (O₂) | Insert a glowing splint into the gas. | The glowing splint relights. |
| Carbon dioxide (CO₂) | Bubble the gas through limewater (calcium hydroxide solution). | Limewater turns milky (cloudy white precipitate of calcium carbonate). |
| Chlorine (Cl₂) | Hold a piece of damp blue litmus paper in the gas. | Turns red then bleaches (turns white). |
These simple identification tests are essential for recognising products of chemical reactions and for ensuring safety in the laboratory.
这些简单的鉴别实验对于确认化学反应产物和确保实验室安全至关重要。
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