📚 AQA International A-Level Chemistry Fundamental Skills | AQA国际A-Level化学基础技能
The AQA International A-Level Chemistry specification expects you to use a common set of practical, mathematical and data-handling skills. This revision guide summarises the fundamental skills booklet content for chemistry, including units, uncertainties, mole calculations, titrations, graphs and energy changes.
AQA国际A-Level化学课程要求你掌握一套共同的实验、数学和数据处理技能。本篇复习指南总结了化学基础技能手册的核心内容，包括单位、不确定度、摩尔计算、滴定、图像和能量变化。
1. SI Units, Prefixes and Conversions | 国际单位制、词头与单位换算
You must be confident with SI base units and common prefixes such as kilo (k, 10³), centi (c, 10⁻²), milli (m, 10⁻³) and micro (μ, 10⁻⁶). In chemistry, volume is often quoted in cm³, so you must convert cm³ to dm³ by dividing by 1000.
你必须熟悉SI基本单位和常用词头，例如千(k, 10³)、厘(c, 10⁻²)、毫(m, 10⁻³)和微(μ, 10⁻⁶)。化学中体积常用cm³表示，因此必须将cm³除以1000换算为dm³。
1 dm³ = 1000 cm³
Always show units in calculations and cancel them correctly. For example, when using concentration in mol dm⁻³ and volume in cm³, first convert the volume to dm³.
计算中始终写出单位并正确约去。例如，当浓度单位为mol dm⁻³而体积单位为cm³时，应先将体积换算为dm³。
2. Significant Figures and Decimal Places | 有效数字与小数位数
Significant figures (s.f.) include all certain digits plus the first uncertain digit. Leading zeros are not significant, but zeros between non-zero digits and trailing zeros after a decimal point are significant.
有效数字(s.f.)包括所有确定数字以及第一位不确定数字。前导零不计入有效数字，但非零数字之间的零以及小数点后的末尾零计入有效数字。
In A-level calculations, give final answers to the least number of significant figures used in the data, unless the question states otherwise. For pH, give answers to two decimal places because the number before the decimal point is a power of ten.
在A-level计算中，最终答案的有效数字通常取所用数据中最少的一位，除非题目另有说明。对于pH值，答案保留两位小数，因为小数点前的数字表示10的幂。
3. Measurement Uncertainty and Error | 测量不确定度与误差
Every measurement has an uncertainty, often taken as half the smallest scale division for analogue instruments or the smallest reading for digital instruments. Combining uncertainties is essential when judging the reliability of a result.
任何测量都具有不确定度，对于模拟仪器通常取最小刻度的一半，对于数字仪器取最小读数。在判断结果可靠性时，需要正确合并不确定度。
- For addition or subtraction, add absolute uncertainties.
- 对于加法或减法，将绝对不确定度相加。
- For multiplication or division, add percentage uncertainties.
- 对于乘法或除法，将百分比不确定度相加。
You should also distinguish between random errors and systematic errors. Repeating measurements reduces random error, while calibration or blank readings can reduce systematic error.
你还应区分随机误差和系统误差。重复测量可以减小随机误差，而校准或空白读数可以减小系统误差。
4. Moles, Molar Mass and the Avogadro Constant | 摩尔、摩尔质量与阿伏伽德罗常数
³ particles, the Avogadro constant. The number of moles n can be calculated from mass m and molar mass M.
摩尔是物质的量的SI单位。1摩尔含有6.02 × 10²³个粒子，即阿伏伽德罗常数。摩尔数n可由质量m和摩尔质量M计算。
n = m ÷ M
For gases, the volume of one mole at room temperature and pressure (RTP) is approximately 24.0 dm³. This conversion is useful for many quantitative problems.
对于气体，在室温和常压(RTP)下，1摩尔气体的体积约为24.0 dm³。该换算在许多定量问题中非常有用。
5. Concentration and Dilution | 浓度与稀释
Concentration c is the amount of solute dissolved in a given volume of solution. The standard unit is mol dm⁻³.
浓度c表示溶解在一定体积溶液中的溶质的量。标准单位为mol dm⁻³。
c = n ÷ V
te stays the same, so c₁V₁ = c₂V₂. Always convert volumes to dm³ when using this equation.
稀释溶液时，溶质的摩尔数保持不变，因此c₁V₁ = c₂V₂。使用该等式时，始终将体积换算为dm³。
6. Empirical and Molecular Formulae | 实验式与分子式
The empirical formula gives the simplest whole-number ratio of atoms in a compound. It is found from percentage or mass composition by dividing each element's mass by its relative atomic mass and then simplifying the ratio.
实验式给出化合物中原子的最简整数比。根据各元素的质量分数或质量组成，将每种元素的质量除以其相对原子质量，然后化简比值即可得到实验式。
The molecular formula is a whole-number multiple of the empirical formula. Use the relative molecular mass to find the multiplier.
分子式是实验式的整数倍。可利用相对分子质量求出该倍数。
7. Titration Technique and Calculations | 滴定操作与计算
Titration determines the concentration of an unknown solution by reacting it with a standard solution. Concordant results should agree within 0.10 cm³ for reliable work.
滴定通过使未知溶液与标准溶液反应来测定其浓度。可靠的实验中，一致性读数应相差不超过0.10 cm³。
and base. Then use n = cV for the known solution and convert to the unknown concentration.
利用配平方程式找出酸和碱之间的摩尔比。然后对已知溶液使用n = cV，并换算为未知溶液浓度。
For example, in the reaction H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O, the mole ratio is 1:2.
例如，在反应 H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O 中，摩尔比为1:2。
8. Ideal Gas Equation | 理想气体方程
The ideal gas equation links pressure p, volume V, amount of gas n and temperature T.
理想气体方程将压强p、体积V、气体物质的量n和温度T联系起来。
pV = nRT
Use p in Pa, V in m³, n in mol and T in K. The gas
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