📚 Year 10 WJEC Chemistry: Formula & Theorem Quick Reference Handbook | Year 10 WJEC 化学：公式定理速查手册
This quick reference handbook brings together all the essential formulae, theorems and quantitative relationships you need for Year 10 WJEC Chemistry. Use it alongside your class notes and past papers to revise efficiently. Every key idea is presented first in English and then in Chinese, ensuring clarity and helping you build fluency in scientific terms.
这本速查手册汇总了 Year 10 WJEC 化学课程中所有必备的公式、定理与定量关系。配合课堂笔记和往年真题使用，可以高效复习。每一个关键知识点都先以英文阐述，再给出中文对照，确保理解清晰，帮助你在科学术语方面建立双语熟练度。
1. Relative Atomic Mass & Relative Molecular Mass | 相对原子质量与相对分子质量
Aᵣ = average mass of an atom ÷ 1/12 mass of a ¹²C atom
Relative atomic mass (Aᵣ) is a dimensionless number that compares the average mass of an atom of an element to 1/12 the mass of a carbon-12 atom. It accounts for all naturally occurring isotopes. The relative molecular (or formula) mass Mᵣ is found by adding together the Aᵣ values of all the atoms in a chemical formula.
相对原子质量（Aᵣ）是一个无量纲数，表示某元素一个原子的平均质量与一个碳-12 原子质量的 1/12 之比。它考虑了所有天然同位素。相对分子质量（或式量）Mᵣ 通过将化学式中所有原子的 Aᵣ 相加得到。
Example/范例:
For H₂O: Mᵣ = (2 × 1) + 16 = 18
对于 H₂O：Mᵣ = (2 × 1) + 16 = 18
2. The Mole & Molar Mass | 摩尔与摩尔质量
n = m / M
nt). The molar mass (M) is the mass of one mole, expressed in g mol⁻¹. The number of moles (n) can be calculated by dividing the mass (m) by the molar mass (M). This relationship is the foundation of all quantitative chemistry.
一摩尔任何物质含有 6.02 × 10²³ 个粒子（阿伏伽德罗常数）。摩尔质量（M）是一摩尔物质的质量，单位为 g mol⁻¹。物质的量（n）可通过质量（m）除以摩尔质量（M）计算。这个关系是所有定量化学的基础。
3. Mass-Mole Conversions | 质量与摩尔之间的换算
mass = n × M and number of particles = n × 6.02 × 10²³
Once the number of moles is known, the mass of a substance can be found by multiplying moles by molar mass. Similarly, the number of atoms, molecules or ions is obtained by multiplying the number of moles by the Avogadro constant. These conversions are essential when interpreting balanced equations in terms of reacting masses.
知道物质的量后，物质的质量可以通过摩尔数乘以摩尔质量得出。同样，原子、分子或离子的个数可以用物质的量乘以阿伏伽德罗常数求得。在用反应方程式计算反应质量时，这些换算是必不可少的。
4. Balancing Equations & Conservation of Mass | 配平方程式与质量守恒定律
Total mass of reactants = Total mass of products
Atoms are neither created nor destroyed in a chemical reaction. This is the law of conservation of mass. A balanced symbol equation must have the same number of each type of atom on both sides. State symbols (s), (l), (g) and (aq) show the physical states and help explain apparent mass changes caused by gases.
化学反应中原子既不会凭空产生也不会消失，这就是质量守恒定律。配平的化学方程式两边必须拥有各种原子的相同数目。状态符号 (s)、(l)、(g) 和 (aq) 表示物质状态，并有助于解释由气体造成的表观质量变化。
5. Concentration of Solutions | 溶液的浓度
c = n / V (V in dm³)
Concentration is measured in mol dm⁻³. It can be calculated by dividing the number of moles of solute by the volume of solution in cubic decimetres. To convert cm³ to dm³, divide by 1000. This formula is used extensively in volumetric analysis and titrations.
浓度单位为 mol dm⁻³，可通过溶质的物质的量除以溶液的体积（立方分米）来计算。将 cm³ 转换为 dm³ 需除以 1000。该公式广泛用于容量分析和滴定实验中。
6. Molar Volume of Gases | 气体的摩尔体积
Volume of gas (dm³) = n × 24 (at room temperature and pressure)
At room temperature and pressure (RTP, about 20 °C and 1 atm), one mole of any gas occupies approximately 24 dm³. This means the amount of gas in moles can be found directly from its measured volume, and vice versa. The relationship holds for all ideal gases.
在室温和常压下（RTP，约 20 °C 和 1 个大气压），一摩尔任何气体的体积约为 24 dm³。这意味着可以直接从气体体积求出物质的量，反之亦然。该关系适用于所有理想气体。
7. Rate of Reaction | 反应速率
Mean rate = quantity of reactant used or product formed ÷ time
The rate of a chemical reaction can be expressed as the change in concentration, mass or volume of a reactant or product per unit time. Factors affecting rate include temperature, concentration, surface area and catalysts. Collision theory explains that particles must collide with sufficient activation energy for a reaction to occur.
化学反应速率可以用单位时间内反应物或产物的浓度、质量或体积的变化量来表示。影响速率的因素包括温度、浓度、表面积和催化剂。碰撞理论解释，粒子必须以足够的活化能发生有效碰撞，反应才能进行。
8. Reversible Reactions & Equilibrium | 可逆反应与平衡
At equilibrium: rate of forward reaction = rate of reverse reaction
In a reversible reaction, the products can react to re-form the reactants. When the forward and reverse rates become equal, the system reaches dynamic equilibrium. Le Chatelier's principle states that if a system at equilibrium is disturbed, it will shift to oppose the change. Temperature, pressure and concentration changes all affect the position of equilibrium.
在可逆反应中，产物可以重新反应生成反应物。当正逆反应速率相等时，体系达到动态平衡。勒夏特列原理指出，如果处于平衡的体系受到干扰，平衡会向减弱这种改变的方向移动。温度、压强和浓度的变化都会影响平衡位置。
9. Percentage Yield & Atom Economy | 百分产率与原子经济性
% Yield = (actual mass / theoretical mass) × 100
% Atom economy = (Mᵣ of desired product / sum of Mᵣ of all reactants) × 100
Percentage yield compares the amount of product actually obtained to the maximum theoretical amount, revealing losses during synthesis. Atom economy measures how efficiently reactant atoms are incorporated into the desired product. High atom economy reduces waste and supports green chemistry principles.
百分产率比较实际得到的产品量与理论最大量，揭示合成过程中的损失。原子经济性衡量反应物原子被有效利用到目标产物中的效率。高原子经济性可以减少废弃物，符合绿色化学的原则。
10. Acid-Base Titration Calculations | 酸碱滴定计算
For a 1:1 reaction: c₁V₁ = c₂V₂ and n = c × V
quals that for the base. For other stoichiometric ratios, use the formula: nₐ / (cₐVₐ) = nb / (cbV ion results allow the determination of an unknown concentration or the purity of a sample.
当酸和碱以 1:1 摩尔比反应时，酸的浓度乘以体积等于碱的浓度乘以体积。对于其他化学计量比，需使用公式 nₐ / (cₐVₐ) = nb / (cbV_b)。滴定结果可用于测定未知浓度或样品纯度。
11. Electrolysis Calculations | 电解计算
charge (Q) = current (I) × time (t) and moles of electrons = Q / 96500
amperes) multiplied by time (seconds). One mole of electrons carries 96500 C (Faraday constant). The mass of a product can be calculated using: mass = (M × I × t) / (n × 96500), where n is the number of electrons in the half-equation.
定量电解将电极上析出的物质质量与通过的电量联系起来。电量（库仑）等于电流（安培）乘以时间（秒）。一摩尔电子携带 96500 库仑电量（法拉第常数）。产品的质量可用公式 mass = (M × I × t) / (n × 96500) 计算，其中 n 是半反应中的电子数。
12. Bond Energy & Enthalpy Change | 键能与焓变
ΔH = Σ (bond energies broken) − Σ (bond energies formed)
In a chemical reaction, bonds in the reactants are broken (energy absorbed) and new bonds in the products are formed (energy released). The enthalpy change (ΔH) is the difference between the total energy absorbed and total energy released. A negative ΔH indicates an exothermic reaction, while a positive ΔH indicates an endothermic reaction.
化学反应中，反应物中的化学键断裂（吸收能量），产物中形成新化学键（释放能量）。焓变（ΔH）是吸收的总能量与释放的总能量之差。ΔH 为负值表示放热反应，正值表示吸热反应。
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