📚 Year 8 CCEA Chemistry: Formula & Theorem Quick Reference Handbook | Year 8 CCEA 化学：公式定理速查手册
Welcome to your Year 8 CCEA Chemistry quick reference guide. This handbook collects the essential formulas, principles, and laws you need to succeed – from particle theory and chemical formulae to balancing equations and investigating rates of reaction. Use it for revision, homework support, or to build confidence before tests.
欢迎使用 Year 8 CCEA 化学速查手册。我们汇集了从粒子理论、化学式到方程式配平和反应速率探究的所有核心公式、定理和规则。可用于考前复习、作业辅助或巩固基础。
1. States of Matter and Particle Theory | 物质状态与粒子理论
All matter is made up of tiny particles that are constantly moving. The arrangement and movement of these particles determine whether a substance is a solid, a liquid or a gas.
所有物质都由不断运动的微小粒子组成。粒子的排列和运动方式决定了物质是固体、液体还是气体。
In solids, particles are tightly packed in a regular pattern. They vibrate in fixed positions but do not move past one another. Solids have a fixed shape and a fixed volume.
在固体中，粒子紧密排列成规则图案，在固定位置振动，不会相互滑过。固体有固定的形状和体积。
In liquids, particles are close together but can slide past each other. Liquids have a fixed volume but take the shape of their container.
在液体中，粒子相互靠近但能彼此滑动。液体有固定体积，但形状随容器而变。
In gases, particles are far apart and move rapidly in all directions. Gases have no fixed shape or volume and can be compressed easily.
在气体中，粒子相距很远，快速地向四面八方运动。气体没有固定的形状和体积，容易被压缩。
Changes of state are physical changes. During melting, freezing, boiling, condensing and sublimation, the particles themselves do not change – only their arrangement and energy change. Mass is conserved.
状态变化是物理变化。在熔化、凝固、沸腾、凝结和升华过程中，粒子本身不发生变化——改变的只是它们的排列和能量。质量是守恒的。
Theorem – Particle Model: All substances are made up of particles. The particles are in constant motion. There are spaces between the particles. The higher the temperature, the faster the particles move.
定理 – 粒子模型：所有物质都由粒子构成；粒子处于不停的运动中；粒子间存在间隙；温度越高，粒子运动越快。
2. Atoms, Elements and Compounds | 原子、元素与化合物
An atom is the smallest particle of an element that can take part in a chemical reaction. All atoms of a given element have the same number of protons.
原子是能够参与化学反应的元素的最小粒子。同种元素的所有原子质子数相同。
An element is a substance made up of only one type of atom. A compound is a substance made up of two or more different types of atom chemically joined together in fixed proportions.
元素是由同种原子组成的纯净物。化合物是由两种或两种以上不同原子按固定比例化学结合而成的纯净物。
The nucleus of an atom contains protons and neutrons. Electrons orbit the nucleus in shells. Protons have a relative charge of +1, neutrons are neutral, and electrons have a charge of -1.
原子核包含质子和中子。电子在核外分层排布。质子相对电荷为+1，中子不带电，电子电荷为-1。
The atomic number (Z) is equal to the number of protons in the nucleus. The mass number (A) is the total number of protons and neutrons.
原子序数 (Z) 等于原子核内质子数。质量数 (A) 等于质子数与中子数之和。
Number of neutrons = Mass number – Atomic number
中子数 = 质量数 – 原子序数
Relative atomic mass (Aᵣ) ≈ Mass number = Number of protons + Number of neutrons
相对原子质量 (Aᵣ) ≈ 质量数 = 质子数 + 中子数
3. Chemical Symbols and Formulae | 化学符号与化学式
Each element is represented by a unique chemical symbol. The first letter is always a capital letter; if there is a second letter, it is lowercase. For example, C for carbon, Ca for calcium, Cl for chlorine.
每种元素用一个专属的化学符号表示。第一个字母必须大写，若有两个字母则第二个小写。例如，碳为 C，钙为 Ca，氯为 Cl。
A chemical formula shows the types and numbers of atoms in a substance. Subscript numbers indicate how many atoms of each element are present. H₂O means two hydrogen atoms and one oxygen atom.
化学式表示物质中原子的种类和数目。下标数字表示该元素原子的个数。H₂O 表示 2 个氢原子和 1 个氧原子。
When writing formulae for ionic compounds, the total positive charge must balance the total negative charge. Use the 'swap and drop' method: exchange the numerical values of the ion charges and write them as subscripts. Simplify if needed.
书写离子化合物的化学式时，正负总电荷必须平衡。使用“交叉相消”法：交换离子电荷的数值并写成下标，必要时化简。
s: Na⁺ and Cl⁻ → NaCl; Mg²⁺ and Cl⁻ → MgCl₂; Al³⁺ and O²⁻ → Al₂O₃; Ca²⁺ and OH⁻ → Ca(OH)₂.
示例: Na⁺ 与 Cl⁻ → NaCl；Mg²⁺ 与 Cl⁻ → MgCl₂；Al³⁺ 与 O²⁻ → Al₂O₃；Ca²⁺ 与 OH⁻ → Ca(OH)₂。
Rule: In the name of a binary ionic compound, the metal name comes first, followed by the non-metal name ending in '-ide'.
规则：在二元离子化合物的命名中，金属名称在前，非金属名称在后并以“-ide”结尾（中文相应称“化某”）。
4. Writing Balanced Chemical Equations | 书写配平化学方程式
n the left, the products on the right, and an arrow (→) points from reactants to products.
化学方程式用符号和化学式表示化学反应。反应物写在左边，生成物写在右边，中间用箭头 (→) 连接。
In a balanced equation, the number of atoms of each element is the same on both sides. This obeys the Law of Conservation of Mass.
在配平的方程式中，每种元素的原子数目在两边相等，这符合质量守恒定律。
Steps to balance an equation:
配平方程式的步骤：
1. Write the correct formulae for all reactants and products.
1. 正确写出所有反应物和生成物的化学式。
2. Count the number of atoms of each element on both sides.
2. 数出两边每种元素的原子个数。
3. Add large coefficients in front of the formulae to balance the atoms. Never change the small subscript numbers.
3. 在化学式前添加适当的系数使原子数相等。绝不可改动下标数字。
4. Check that all coefficients are in the simplest whole-number ratio.
4. 检查所有系数是否为最简整数比。
Example: H₂ + O₂ → H₂O becomes 2H₂ + O₂ → 2H₂O
例如：H₂ + O₂ → H₂O 配平为 2H₂ + O₂ → 2H₂O
State symbols can be added: (s) solid, (l) liquid, (g) gas, (aq) aqueous solution.
可标注状态符号：(s) 固体，(l) 液体，(g) 气体，(aq) 水溶液。
5. Conservation of Mass | 质量守恒定律
The total mass of the products of a chemical reaction is always equal to the total mass of the reactants. No atoms are created or destroyed; they are only rearranged.
化学反应中，生成物的总质量始终等于反应物的总质量。原子不会被创造或毁灭，只能重新排列。
In an open system where a gas is produced and allowed to escape, the measured mass after the reaction may appear to decrease. In a closed system, where no substances can enter or leave, the mass remains constant.
在敞开体系中，如果生成的气体逸散，测得的反应后质量可能会减小。在密闭体系中，没有物质进出，质量保持不变。
If the mass appears to increase, it is usually because a gas from the air has reacted with the substances. For example, when magnesium burns in air, it combines with oxygen, so the product mass is greater than the original mass of magnesium.
如果质量看似增加，通常是因为空气中的气体参与了反应。例如，镁在空气中燃烧时与氧气结合，生成物的质量比镁条原来的质量大。
Total mass of reactants = Total mass of products
反应物总质量 = 生成物总质量
6. Relative Formula Mass (Mᵣ) | 相对式量 (Mᵣ)
The relative formula mass (Mᵣ) of a compound is found by adding together the relative atomic masses (Aᵣ) of all the atoms in its formula.
化合物的相对式量 (Mᵣ) 等于其化学式中所有原子的相对原子质量 (Aᵣ) 之和。
Mᵣ = Σ (Aᵣ of each element × number of atoms of that element)
Mᵣ = Σ (各元素 Aᵣ × 该元素原子个数)
Example calculations (using Aᵣ values: H=1, C=12, O=16, Na=23, Cl=35.5, Ca=40):
计算示例 (采用 Aᵣ：H=1, C=12, O=16, Na=23, Cl=35.5, Ca=40):
H₂O: (2 × 1) + 16 = 18
H₂O: (2 × 1) + 16 = 18
CO₂: 12 + (2 × 16) = 44
CO₂: 12 + (2 × 16) = 44
NaCl: 23 + 35.5 = 58.5
NaCl: 23 + 35.5 = 58.5
CaCO₃: 40 + 12 + (3 × 16) = 100
CaCO₃: 40 + 12 + (3 × 16) = 100
Relative formula mass has no units. It allows us to compare the masses of different formula units and is essential for calculating reacting masses in later studies.
相对式量没有单位。它可以用来比较不同化学式单元的质量，也是以后计算反应质量的基础。
7. Acids, Alkalis and the pH Scale | 酸、碱与 pH 标度
Acids produce hydrogen ions (H⁺) when dissolved in water. Common acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃).
酸溶于水时会产生氢离子 (H⁺)。常见的酸有盐酸 (HCl)、硫酸 (H₂SO₄) 和硝酸 (HNO₃)。
Alkalis are soluble bases that produce hydroxide ions (OH⁻) in water. Examples include sodium hydroxide (NaOH) and potassium hydroxide (KOH).
碱是能够溶于水并产生氢氧根离子 (OH⁻) 的物质。例如氢氧化钠 (NaOH) 和氢氧化钾 (KOH)。
The pH scale measures how acidic or alkaline a solution is. It ranges from 0 to 14:
pH 标度用来衡量溶液的酸碱度，范围通常为 0 到 14：
pH less than 7 → acidic; pH 7 → neutral; pH greater than 7 → alkaline.
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