📚 AS AQA Chemistry: Insert 2 (January 2021) Explained | AS AQA化学：插页2（2021年1月）详解
The January 2021 AQA AS Chemistry Paper 2 insert (often referred to as ‘Insert 2’) provides two critical pieces of reference data: the Periodic Table and an infrared (IR) absorption frequency table. This insert is designed to be used throughout the examination, allowing you to focus on applying concepts rather than memorising numbers. Mastery of this insert can dramatically improve both your speed and accuracy.
2021年1月AQA AS化学Paper 2的插页（通常称为“插页2”）提供了两类关键参考数据：周期表和红外吸收频率表。这份插页旨在让考生在整场考试中随时查阅，从而专注于应用概念而非记忆数字。熟练掌握这份插页能显著提升你的解题速度和准确率。
1. Overview of Insert 2 | 插页2概述
Insert 2 is specifically provided for Paper 2 (Organic and Physical Chemistry) of the AS specification. It is a double‑sided sheet: one side features the Periodic Table, while the other contains a table of infrared absorption frequencies for the most common functional groups. The same insert is not used for Paper 1, which focuses on Physical and Inorganic Chemistry and supplies only the Periodic Table.
插页2是专为AS大纲中Paper 2（有机与物理化学）提供的参考表。这是一张双面纸：一面为周期表，另一面则为常见官能团的红外吸收频率表。Paper 1（物理与无机化学）不使用这份插页，仅提供周期表。
2. The Periodic Table: Key Features | 周期表：关键特点
The Periodic Table in your insert includes atomic numbers, symbols, and relative atomic masses for all stable elements. It also clearly marks the groups (columns) and periods (rows). For AS chemistry, you need to be comfortable locating elements in Groups 1, 2, 7, and 0, as well as transition metals, and understand how the table is organised into s‑, p‑, and d‑blocks.
插页中的周期表列出了所有稳定元素的原子序数、符号和相对原子质量，并清晰标出了族（列）和周期（行）。在AS化学中，你需要熟练地定位第1、2、7、0族元素以及过渡金属，并理解周期表是如何分为s区、p区和d区的。
The table uses the standard AQA convention: for each element, the larger number is the relative atomic mass and the smaller number is the atomic number. For example, chlorine shows 35.5 and 17, meaning its relative atomic mass is 35.5 and its atomic number is 17.
该表采用AQA标准格式：每个元素的较大数字为相对原子质量，较小数字为原子序数。例如，氯显示为35.5和17，即相对原子质量为35.5，原子序数为17。
3. Using Relative Atomic Masses for Calculations | 使用相对原子质量进行计算
One of the most common uses of the Periodic Table on the insert is to calculate relative formula masses (Mr) and to perform quantitative chemistry. For example, the relative atomic masses of Ca, C and O are 40.1, 12.0 and 16.0 respectively. Hence the Mr of CaCO₃ is 40.1 + 12.0 + (3 × 16.0) = 100.1.
插页中周期表最常见的用途之一是计算相对式量（Mr）并进行定量化学计算。例如，Ca、C和O的相对原子质量分别为40.1、12.0和16.0。因此CaCO₃的Mr为：40.1 + 12.0 + (3 × 16.0) = 100.1。
Mr(CaCO₃) = 40.1 + 12.0 + 3 × 16.0 = 100.1
Always use the precise values given on the insert rather than rounded integers. AQA expects you to use these exact values in your final answer, and failing to do so often leads to loss of marks in multi‑step calculations.
务必使用插页上的精确数值，不要自行四舍五入。AQA要求你在最终答案中使用这些精确数值；在多步计算中若忽略此要求，常常会失分。
4. Electronegativity and Bonding | 电负性与键合
While the insert does not list electronegativity values, the Periodic Table allows you to predict the type of bonding and the polarity of molecules. Electronegativity generally increases across a period and decreases down a group. For example, fluorine is the most electronegative element, while francium is the least.
虽然插页不直接列出电负性数值，但周期表能帮助你预测键合类型和分子的极性。电负性通常在同一周期内从左到右增大，在同一族内从上到下减小。例如，氟是电负性最强的元素，而钫则最弱。
When carbon bonds with a metal, most compounds are ionic; when it bonds with non‑metals such as oxygen or chlorine, the bonds are often polar covalent. Use the relative positions of the elements to assess the electronegativity difference (Δχ) and hence the bond type.
当碳与金属键合时，化合物大多为离子型；当碳与氧或氯等非金属键合时，共价键往往具有极性。通过元素在周期表中的相对位置，可以判断电负性差值（Δχ）以及键的类型。
5. Infrared Spectroscopy: The Data Table | 红外光谱：数据表
The second side of Insert 2 contains the infrared absorption data table. This table lists the wavenumber (in cm⁻¹) where different chemical bonds absorb infrared radiation. The table includes the bond type, the functional group in which it is found, and the approximate absorption range. You are expected to use these values to identify functional groups from a given spectrum.
插页2的另一面是红外吸收数据表，列出了不同化学键吸收红外辐射的波数（单位cm⁻¹）。表格包含键的类型、所在的官能团以及大致吸收范围。你应当会利用这些数值从给定光谱中识别官能团。
IR absorption ranges are expressed in wavenumber (ŵ), the number of wavelengths per centimetre (cm⁻¹).
注意：该表只包含“气态或液态”样品中常见键的信息。所有吸收范围都是近似值，因此你在作答时应引用表中所给的范围，而不必精确到单独一个波数。
6. How to Interpret IR Spectra | 如何解读红外光谱
To identify a functional group from an IR spectrum, locate the strong absorption peaks and match them against the ranges given on the insert. For instance, a strong, sharp peak at about 1710 cm⁻¹ indicates a carbonyl group (C=O) in an aldehyde or ketone. A broad, strong peak between 3230–3550 cm⁻¹ suggests an O–H group in an alcohol.
要从红外光谱中识别官能团，需找到强吸收峰，并将其与插页上的范围对照。例如，约1710 cm⁻¹处的强而尖锐的吸收峰表明醛或酮中存在羰基（C=O）。在3230–3550 cm⁻¹范围内的宽而强的峰则提示醇类中的O–H基团。
Remember that the IR spectrum is not a fingerprint of the whole molecule; only specific bonds give characteristic absorptions. You must also consider the absence of key peaks. For example, the absence of an O–H peak but the presence of C=O strongly suggests a ketone rather than a carboxylic acid (which would also show a broad O–H peak around 2500–3300 cm⁻¹).
请记住，红外光谱并不提供整个分子的“指纹”，只有特定键才有特征吸收。你还需要关注关键峰的缺失。例如，若没有O–H峰但有C=O峰，则更可能是酮而非羧酸（羧酸会在2500–3300 cm⁻¹附近出现宽的O–H峰）。
7. Common IR Absorption Values | 常见红外吸收值
The following table summarises the absorption data typically found on Insert 2. Note that these values are exactly as they appear on the AQA data sheet.
下表总结了插页2上常见的红外吸收数据。注意，这些数值与AQA数据表上的完全一致。
| Bond | Functional Group | Wavenumber / cm⁻¹ | Appearance |
| C–O | Alcohols, ethers, esters, carboxylic acids | 1000–1300 | Strong |
| C=O | Aldehydes, ketones, carboxylic acids, esters | 1630–1820 | Strong |
| C=C | Alkenes | 1620–1680 | Variable |
| C≡C | Alkynes | 2100–2260 | Variable |
| O–H | Alcohols (hydrogen bonded) | 3230–3550 | Strong, broad |
| O–H | Carboxylic acids | 2500–3300 | Strong, very broad |
| N–H | Amines | 3300–3500 | Medium |
| C–H | Alkyl groups | 2850–2950 | Strong |
These ranges overlap for some bonds (e.g., C=C and C=O), so it is vital to consider the shape and intensity of the peak as well as the presence of other absorptions.
这些范围对于某些键（如C=C和C=O）会有重叠，因此必须同时考虑峰的形状、强度以及其他吸收峰的存在。
8. Worked Example: Identifying an Unknown Compound | 例题：鉴定未知化合物
A compound with molecular formula C₃H₆O₂ shows a strong IR absorption at 1710 cm⁻¹ and a very broad peak between 2500–3300 cm⁻¹. Identify the functional group present.
某化合物的分子式为C₃H₆O₂，其红外光谱在1710 cm⁻¹处有强吸收，并在2500–3300 cm⁻¹范围内有非常宽的峰。请指出所含的官能团。
Solution: The strong peak at 1710 cm⁻¹ confirms a carbonyl group (C=O). The very broad peak at 2500–3300 cm⁻¹ is characteristic of the O–H group in a carboxylic acid. Therefore the compound is propanoic acid (CH₃CH₂COOH).
解答：1710 cm⁻¹处的强峰证实有羰基（C=O）；2500–3300 cm⁻¹处的极宽峰是羧酸中O–H的特征峰。因此该化合物为丙酸（CH₃CH₂COOH）。
This example illustrates exactly how to combine IR data with other information (such as molecular formula) to deduce the structure. Always quote the wavenumber ranges from the insert in your answer.
这个例子展示了如何将红外数据与其他信息（如分子式）结合来推断结构。在作答时，一定要引用插页上的波数范围。
9. Avoiding Common Mistakes | 避免常见错误
Many students lose marks on IR questions because they quote approximate values without giving a range, or they confuse the absorption ranges for alcohols and carboxylic acids. A common error is to state that an O–H peak at 3300 cm⁻¹ is from an alcohol, when the absence of a C=O peak and the broadness of the peak may suggest something different.
许多学生在红外题目上丢分，是因为他们只写近似值而没有给出范围，或者混淆了醇和羧酸中O–H的吸收范围。常见的错误是看到3300 cm⁻¹处的O–H峰就断定是醇，而忽略了C=O峰的出现以及峰形特征。
- Always mention the shape and intensity of the peak (“strong”, “broad”, “sharp”) where relevant.
- Use the exact wavenumber ranges given on the insert, not general values you have memorised.
- When more than one functional group is present, list all peaks that match the observed absorptions.
中文要点：
- 在描述峰时，必须说明其形状和强度（如“强”、“宽”、“尖锐”）。
- 使用插页上的精确波数范围，而不是记忆中的大概数值。
- 若分子中存在多个官能团，应把所有与观察到的吸收对应的峰都列出。
10. Exam Strategy with Insert 2 | 考试策略：利用插页2
To maximise your marks, familiarise yourself with the insert before the exam. Practice locating relative atomic masses quickly and reading the IR table accurately. In the exam, keep the insert open at all times; do not rely on memory for values that are provided.
为了最大化得分，请在考前熟悉插页。练习快速查找相对原子质量以及准确阅读红外表。考试时保持插页始终展开，凡是提供的数值都不要依赖记忆。
For calculations, write down the masses you use and show your working clearly; this ensures you receive method marks even if your final answer is wrong. For IR questions, always quote the wavenumber range and the functional group it indicates, and state whether the peak is strong or broad if that is relevant.
在计算题中，写下你所用的质量并清晰展示过程，这样即使最终答案错误也能获得方法分。在红外题中，务必引用波数范围和对应的官能团，并说明峰是强还是宽（如适用）。
Finally, remember that the insert is the same for all candidates. Using it effectively gives you an equal opportunity to demonstrate your knowledge, so make it your best friend on exam day.
最后请记住，插页对所有考生都是一样的。有效利用它让你能公平地展示知识，因此在考试当天把它当作你最得力的助手。
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