📚 Year 7 WJEC Chemistry: Formula and Theorem Quick Reference Handbook | Year 7 WJEC 化学：公式定理速查手册
This handbook brings together all the essential formulas and key theorems you need for Year 7 WJEC Chemistry. Use it to check definitions, practise applying equations, and make sure you're confident with the particle model, symbols, conservation of mass, acids and alkalis, rates, and separation methods. Keep it handy for revision and quick-fire testing.
本手册汇集了 Year 7 WJEC 化学所需的所有基本公式和关键定理。你可以用它来核对定义、练习应用公式，并确保自己对粒子模型、符号、质量守恒、酸与碱、反应速率以及分离方法充满信心。请将手册放在手边，用于复习和快速自测。
1. Particle Theory of Matter | 物质的粒子理论
The particle theory states that all matter is made up of tiny particles that are constantly moving. The amount of energy the particles have determines how fast they move and how far apart they are.
粒子理论指出，所有物质都由不断运动的微小粒子组成。粒子所具有的能量多少决定了它们运动的速度以及彼此之间的距离。
Key assumptions of the particle theory: particles are extremely small; there are spaces between particles; particles are in constant, random motion; particles attract each other when close together.
粒子理论的关键假设：粒子极其微小；粒子之间存在空间；粒子处于永恒且随机的运动中；当粒子彼此靠近时会相互吸引。
Theorem (Relationship between energy and motion): As the kinetic energy of particles increases, the speed of the particles increases, and the distance between them tends to increase if no external constraints are applied.
定理（能量与运动的关系）： 随着粒子动能的增加，粒子运动的速度会增大，如果没有外部约束，它们之间的距离也会趋于增大。
2. States of Matter | 物质的状态
The three common states of matter are solid, liquid and gas. The behaviour of particles in each state can be described using the particle theory.
物质的三种常见状态是固体、液体和气体。可以利用粒子理论来描述每种状态下粒子的行为。
In solids, particles are packed tightly in a regular pattern, they vibrate in fixed positions, and they have the least energy.
在固体中，粒子紧密排列，形成规则的结构，在固定位置上振动，能量最低。
In liquids, particles are close together but not in a fixed pattern; they can slide past each other and take the shape of the container.
在液体中，粒子相互靠近但没有固定结构；它们能够彼此滑动，呈容器的形状。
In gases, particles are far apart, move rapidly in all directions, and have the most energy.
在气体中，粒子之间距离很远，朝各个方向快速运动，能量最高。
Formula – Density: . This formula helps compare how heavy a substance is for its size. Solids are usually denser than liquids and gases because particles are packed more tightly.
公式 – 密度: 密度 = 质量 / 体积。符号表示为 ρ = m / V（单位为 g/cm³ 或 kg/m³）。这个公式有助于比较一种物质相对于其体积的重量。固体通常比液体和气体密度更高，因为粒子排列更紧密。
3. Physical and Chemical Changes | 物理变化与化学变化
A physical change alters the state or appearance of a substance, but no new substance is formed. Examples: melting, freezing, boiling, condensing, dissolving, cutting.
物理变化改变物质的状态或外观，但没有生成新的物质。例如：熔化、凝固、沸腾、冷凝、溶解、切割。
A chemical change (a chemical reaction) produces one or more new substances with different properties. Signs include colour change, temperature change, gas production, or formation of a precipitate. Chemical changes are usually irreversible.
化学变化（化学反应）生成一种或多种性质不同的新物质。迹象包括颜色变化、温度变化、有气体产生或生成沉淀。化学变化通常是不可逆的。
Theorem – Conservation of mass: In a chemical reaction, the total mass of the reactants equals the total mass of the products. No atoms are lost or created; they are just rearranged.
定理 – 质量守恒: 在化学反应中，反应物的总质量等于生成物的总质量。原子没有被消灭或创造，它们只是重新排列了。
4. Elements, Compounds and Mixtures | 元素、化合物和混合物
An element is a pure substance made of only one type of atom. Elements cannot be broken down into simpler substances by chemical means. Examples: oxygen (O), hydrogen (H), iron (Fe).
元素是由同一种原子组成的纯物质。通过化学方法无法将元素分解为更简单的物质。例子：氧（O）、氢（H）、铁（Fe）。
A compound is a pure substance made of two or more different types of atom chemically joined together in fixed proportions. Compounds have properties different from their constituent elements. Example: water (H₂O), always two hydrogen atoms bonded to one oxygen atom.
化合物是由两种或多种不同原子通过化学键以固定比例结合而成的纯物质。化合物的性质与其组成元素不同。例子：水（H₂O），总是两个氢原子与一个氧原子键合。
A mixture contains two or more different substances (elements or compounds) that are not chemically joined. The components keep their own properties and can be separated by physical techniques. Mixtures do not have a fixed composition. Example: air, salty water.
混合物含有两种或多种未经过化学键合的不同的物质（元素或化合物）。各组分保留自身的性质，可以通过物理方法进行分离。混合物没有固定的组成。例子：空气、盐水。
5. Atomic Structure and the Periodic Table | 原子结构与周期表
Atoms are the smallest particles of an element that still have the properties of that element. Each atom consists of a central nucleus containing protons (positive charge) and neutrons (no charge), with electrons (negative charge) moving around the nucleus in shells.
原子是元素的最小粒子，仍保持该元素的性质。每个原子由一个中心原子核和电子组成，原子核包含质子（带正电荷）和中子（不带电荷），电子（带负电荷）在核外的电子层中运动。
e +1. Neutron: relative mass 1, charge 0. Electron: relative mass ≈ 0 (1/1840), charge -1.
重要粒子的质量和电荷：质子：相对质量 1，电荷 +1。中子：相对质量 1，电荷 0。电子：相对质量约为 0（1/1840），电荷 -1。
The atomic (proton) number is the number of protons in an atom. It determines the element. The mass number is the total number of protons + neutrons in the nucleus.
原子序数（质子数）是原子中质子的个数。它决定了元素的种类。质量数是原子核中质子数与中子数的总和。
The periodic table arranges all known elements in order of increasing atomic number. Elements in the same group (vertical column) have similar chemical properties because they have the same number of electrons in their outer shell.
周期表按照原子序数递增的顺序排列所有已知元素。同一族（竖列）的元素具有相似的化学性质，因为它们最外层电子数相同。
6. Chemical Symbols and Formulae | 化学符号与化学式
Each element is represented by a one- or two-letter chemical symbol. The first letter is always a capital, the second (if present) is lower case. Examples: C for carbon, O for oxygen, Na for sodium, Fe for iron.
每种元素用一个或两个字母的化学符号表示。第一个字母总是大写，第二个字母（如果有）为小写。例子：碳用 C，氧用 O，钠用 Na，铁用 Fe。
A chemical formula shows the types and numbers of atoms in a compound. The number of each type of atom is shown as a subscript. If there is no subscript, it means one atom. Examples: CO₂ (one carbon, two oxygens), H₂SO₄ (two hydrogens, one sulfur, four oxygens).
化学式表示了化合物中原子的种类和个数。每种原子的个数用下标表示。如果没有下标，则表示该原子为一个。例子：CO₂（一个碳原子，两个氧原子），H₂SO₄（两个氢原子，一个硫原子，四个氧原子）。
Formula – working out relative formula mass (simple): eriodic table. Example: H₂O = (2 × 1) + (1 × 16) = 18. For Year 7, use whole numbers only.
公式 – 计算相对化学式量（简单）: 对于化合物，将化学式中所有原子的相对原子质量（Aᵣ）相加。相对原子质量可以在周期表中找到。例子：H₂O = (2 × 1) + (1 × 16) = 18。对于 Year 7，只使用整数进行计算。
7. Chemical Reactions and Equations | 化学反应与方程式
es) are written on the right, separated by an arrow (→). Conditions like heating can be written above the arrow.
化学反应用文字方程式表示。反应物（起始物质）写在左侧，生成物（新物质）写在右侧，用箭头（→）分隔。加热等条件可以写在箭头上方。
ls us what substances react and what is produced, but it does not show the number of atoms involved. For Year 7, focus on word equations and begin to understand symbol equations.
文字方程式举例：甲烷 + 氧气 → 二氧化碳 + 水。这告诉我们什么物质参与了反应、生成了什么，但没有显示所涉及的原子数目。Year 7 阶段重点学习文字方程式，并开始理解符号方程式。
A balanced symbol equation uses chemical symbols and formulae, and follows the law of conservation of mass. The number of atoms of each element must be the same on both sides of the equation. Coefficients (large numbers in front) are used to balance equations.
配平的符号方程式使用化学符号和化学式，且遵循质量守恒定律。方程式两侧每种元素的原子数目必须相等。使用系数（前面的整数）来配平方程式。
o become: 2H₂ + O₂ → 2H₂O. Always check: 4 hydrogen atoms and 2 oxygen atoms on each side.
配平示例：H₂ + O₂ → H₂O 需要在 H₂ 前配系数 2、在 H₂O 前配系数 2，变为：2H₂ + O₂ → 2H₂O。务必检查：两边都有 4 个氢原子和 2 个氧原子。
8. Acids and Alkalis | 酸和碱
Acids are substances that have a pH less than 7. Common laboratory acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃). Acids taste sour (but never taste in the lab) and turn blue litmus paper red.
酸是 pH 值小于 7 的物质。常见的实验室酸包括盐酸（HCl）、硫酸（H₂SO₄）和硝酸（HNO₃）。酸尝起来有酸味（但实验室绝不可品尝），并能将蓝色石蕊试纸变为红色。
Alkalis are soluble bases that have a pH greater than 7. Common alkalis include sodium hydroxide (NaOH), potassium hydroxide (KOH) and calcium hydroxide (Ca(OH)₂). Alkalis feel soapy and turn red litmus paper blue.
碱是可溶性的碱性物质，pH 值大于 7。常见的碱包括氢氧化钠（NaOH）、氢氧化钾（KOH）和氢氧化钙（Ca(OH)₂）。碱摸起来有滑腻感，能将红色石蕊试纸变为蓝色。
Theorem – Neutralisation: + water. The H⁺ ions from the acid combine with the OH⁻ ions from the alkali to produce water molecules (H₂O). This is a pH-changing reaction towards neutral (pH 7).
定理 – 中和反应: 当酸与碱发生反应时，生成盐和水。通用文字方程式为：酸 + 碱 → 盐 + 水。酸中的 H⁺ 离子与碱中的 OH⁻ 离子结合生成水分子（H₂O）。这是一个使 pH 趋向中性（pH 7）的反应。
on: HCl + NaOH → NaCl + H₂O. This is the neutralisation reaction used to make common salt.
例子：盐酸 + 氢氧化钠 → 氯化钠 + 水。方程式：HCl + NaOH → NaCl + H₂O。这就是用来制备普通食盐的中和反应。
9. Rate of Reaction | 反应速率
The rate of a chemical reaction tells us how quickly reactants are used up or products are formed. A fast reaction completes in a short time (e.g. explosions), while a slow reaction may take years (e.g. rusting).
化学反应速率告诉我们反应物被消耗殆尽或生成物形成的快慢程度。快速反应可在短时间内完成（如爆炸），而缓慢反应可能要花上数年（如生锈）。
Formula – Average rate of reaction: Rate = Quantity of product formed / Time taken OR be g/s, cm³/s, etc. This formula can be used to compare rates under different conditions.
公式 – 平均反应速率: 速率 = 生成的生成物的量 / 所用时间 或 速率 = 消耗的反应物的质量 / 所用时间。单位可以是 g/s、cm³/s 等。这个公式可用于比较不同条件下的反应速率。
Factors affecting rate (collision theory principle): increasing temperature, increasing concentration of a solution, increasing surface area of a solid, or using a catalyst all increase the rate of reaction. This is because these changes increase the frequency of successful collisions between reactant particles.
影响速率的因素（碰撞理论原理）：升高温度、增大溶液的浓度、增大固体的表面积，或使用催化剂，均会加快反应速率。这是因为这些变化增加了反应物粒子之间有效碰撞的频率。
For gases, increasing pressure also increases rate by forcing particles closer together, leading to more frequent collisions.
对于气体而言，增大压强也会通过使粒子靠得更近、导致碰撞更频繁，从而提高反应速率。
10. Separation Techniques | 分离技术
Mixtures can be separated using physical methods based on differences in physical properties such as boiling point, particle size, solubility, or magnetism.
可以利用物理性质的差异，如沸点、粒径、溶解度或磁性，通过物理方法对混合物进行分离。
Key separation techniques for Year 7:
Filtration: separates an insoluble solid from a liquid using filter paper. The solid stays as residue, the liquid passes through as filtrate. Example: sand from water.
过滤：使用滤纸将不溶性固体与液体分离。固体作为残渣留下，液体透过滤纸成为滤液。例子：沙子与水分离。
Evaporation: removes a soluble solid from a liquid by heating so the liquid evaporates, leaving the solid behind. Example: salt from salty water.
蒸发：通过加热使液体蒸发，留下可溶性固体，从而将其与液体分离。例子：从盐水中获取盐。
Simple distillation: separates a liquid from a solution or mixture of liquids with different boiling points. The liquid with the lower boiling point evaporates first, then condenses and is collected. Example: pure water from ink.
简单蒸馏：用于从溶液或沸点不同的液体混合物中分离出液体。沸点较低的液体先蒸发，然后冷凝并收集。例子：从墨水中提取纯水。
Chromatography: separates dissolved substances that have different solubilities. The substances travel different distances up the chromatography paper. Example: separating colours in ink.
色谱法：分离具有不同溶解度的已溶解物质。这些物质在色谱纸上移动的距离不同。例子：分离墨水中的不同颜色。
Magnetism: separates magnetic materials from non-magnetic ones using a magnet. Example: iron filings from sand.
磁选：使用磁铁将磁性物质与非磁性物质分离。例子：从沙子中分离铁屑。
Published by TutorHao | Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图