📚 AQA AS Chemistry Unit 3 Jan 2019 Insert: Practical Skills and Exam Guide | AQA AS化学Unit 3 2019年1月插页：实验技能与考试指南
The AS AQA Chemistry Unit 3 paper tests practical and investigative skills, and in the January 2019 sitting it was supported by a separate insert. That insert provides the experimental context, results tables, risk-assessment notes and sometimes additional instructions that are not printed in the main question paper. To score well, you must read the insert as carefully as the questions themselves.
AQA AS 化学 Unit 3 试卷考查实验与探究技能，2019年1月的考试配有一份独立的插页。插页提供实验背景、结果表格、风险评估说明，有时还包含主试卷中未印出的额外指令。想要取得好成绩，你必须像阅读题目一样仔细阅读插页。
1. What the Unit 3 Insert Is and Why It Matters | 什么是Unit 3插页以及它为何重要
In AQA AS Chemistry Unit 3, the insert is a separate booklet placed inside the question paper. For the January 2019 sitting, candidates received the insert alongside the Unit 3 written paper. The insert is not simply background reading; it contains the raw data, headings, and practical details that questions refer to directly.
在AQA AS化学Unit 3中，插页是放在试卷内的一份独立小册子。2019年1月的考试中，考生在Unit 3笔试时同时拿到这份插页。插页不只是背景阅读材料；它包含题目直接引用的原始数据、标题和实验细节。
Many students skim the insert and then wonder why their answers do not match the mark scheme. The exam board often awards marks for selecting the correct column, using the correct unit, or identifying a limitation only visible in the insert. Treat the insert as part of the question paper.
许多学生草草浏览插页，随后不明白为何自己的答案与评分方案不符。考试局经常根据你是否选择了正确的数据列、使用了正确的单位，或是否指出了只在插页中可见的局限性来给分。要把插页当作试卷的一部分来对待。
2. What the January 2019 Insert Typically Contains | 2019年1月插页通常包含什么
The January 2019 AQA AS Unit 3 insert was designed around a practical task, and it typically presented the title of the experiment, a brief method summary, a results table with some completed values, and a list of hazards or control variables. You were expected to use the table for calculations, graph plotting, and evaluations.
2019年1月AQA AS Unit 3插页围绕一个实验任务设计，通常给出实验标题、简要方法摘要、部分已填写的结果表，以及一份危险或控制变量清单。你应当利用这个表格进行计算、作图并作出评价。
Even if your school carried out a slightly different experiment, the insert allows every candidate to work from the same data. This means your answers must be consistent with the numbers shown, not with your own experimental results if they differed.
即使你所在学校完成的实验略有不同，插页也让所有考生使用同一组数据作答。这意味着你的答案必须与插页显示的数字一致，而不是与你自己的实验数据一致，如果两者有差异的话。
3. Reading the Results Table: Variables, Headings and Units | 阅读结果表：变量、标题和单位
A typical insert table might show temperature, time for a visual change, and a calculated value such as 1/time. The headings are not decorations; they tell you what has been measured and what has been derived. For example, if the heading is “1/t / s⁻¹”, the unit tells you the values are reciprocal seconds.
典型的插页表格可能显示温度、发生可见变化所需的时间，以及诸如1/时间之类的计算值。标题不是装饰；它们告诉你什么是测量值，什么是推导值。例如，如果标题是“1/t / s⁻¹”，单位告诉你这些值是每秒的倒数。
| Temperature / °C | Time for cross to disappear / s | 1 / time / s⁻¹ |
|---|---|---|
| 20 | 182 | 0.00549 |
| 30 | 95 | 0.0105 |
| 40 | 51 | 0.0196 |
| 50 | 30 | 0.0333 |
When you read a table like this, identify the independent variable, the dependent variable and the derived variable. The independent variable is the one you change, usually temperature or concentration. The dependent variable is the one you measure, usually time. The derived variable is calculated to make the relationship easier to plot.
阅读这样的表格时，要识别自变量、因变量和推导变量。自变量是你改变的变量，通常是温度或浓度。因变量是你测量的变量，通常是时间。推导变量是为了让关系更容易绘图而计算出来的。
4. Key Calculations You Must Show in Unit 3 | Unit 3中你必须展示的关键计算
The insert often gives experimental values, but the examiners expect you to process them. You will regularly need to calculate moles, concentration, percentage yield, atom economy, or percentage uncertainty. Always show your working in a clear, logical order because method marks are available even if the final answer is wrong.
插页通常给出实验数值，但考官期望你对它们进行处理。你经常需要计算摩尔、浓度、百分比产率、原子经济性或百分比不确定度。始终清晰、有逻辑地展示计算过程，因为即使最终答案错误，方法分仍然可以获得。
The relationship between moles, concentration and volume in solution is central:
n = c × V
其中 n 是物质的量（mol），c 是浓度（mol dm⁻³），V 是体积（dm³）。
In the January 2019 Unit 3 insert, if a titration gave a mean titre of 24.50 cm³ of 0.100 mol dm⁻³ hydrochloric acid against 25.0 cm³ of sodium hydroxide, the moles of HCl used were:
在2019年1月Unit 3插页中，如果滴定使用0.100 mol dm⁻³盐酸的平均滴定体积为24.50 cm³，滴定25.0 cm³氢氧化钠溶液，则所用的HCl摩尔数为：
n(HCl) = 0.100 × (24.50 ÷ 1000) = 0.00245 mol
Since the reaction is 1:1, the amount of NaOH is also 0.00245 mol. The concentration is therefore:
由于反应为1:1，NaOH的物质的量也为0.00245 mol。因此其浓度为：
c(NaOH) = 0.00245 ÷ (25.0 ÷ 1000) = 0.0980 mol dm⁻³
Notice that you must convert cm³ to dm³ before using the equation. A common error is to forget the ÷1000 step, leading to an answer one thousand times too large.
请注意，在使用公式之前必须将cm³转换为dm³。常见错误是忘记除以1000，导致答案大了1000倍。
5. Dealing with Uncertainties and Percentage Errors | 处理不确定度和百分比误差
Practical papers often ask you to calculate the percentage uncertainty in a measurement. The formula is:
实验试卷常要求你计算测量值的百分比不确定度。公式为：
Percentage uncertainty = (absolute uncertainty ÷ measured value) × 100%
If a thermometer reads to ±0.5 °C and the temperature change is 22.0 °C, the percentage uncertainty in that temperature change is:
如果一支温度计的读数误差为±0.5 °C，温度变化为22.0 °C，则该温度变化的百分比不确定度为：
(0.5 ÷ 22.0) × 100% = 2.27%
For titrations, the uncertainty is often bigger because two readings are taken. A burette reading has an uncertainty of ±0.05 cm³, but the difference between initial and final readings has a total uncertainty of ±0.10 cm³. If the titre is 24.50 cm³, the percentage uncertainty is:
对于滴定，不确定度通常更大，因为需要读取两次。滴定管读数的误差为±0.05 cm³，但初始和最终读数之差的总不确定度为±0.10 cm³。如果滴定体积为24.50 cm³，则百分比不确定度为：
(0.10 ÷ 24.50) × 100% = 0.408%
Always quote final uncertainties to a sensible number of significant figures and include the % sign.
最终的不确定度要使用合理的有效数字位数，并加上%符号。
6. Plotting and Interpreting Graphs from Insert Data | 根据插页数据作图并解释图像
AQA Unit 3 frequently asks you to plot a graph from the insert data. If the relationship is between temperature and rate, you may be asked to plot 1/time against temperature. The graph is usually a curve, and you may need to describe the trend rather than calculate a gradient.
AQA Unit 3经常要求你根据插页数据绘制图像。如果关系是温度与速率之间的关系，你可能需要绘制1/时间对温度的图。图像通常是曲线，你可能只需要描述趋势而不必计算斜率。
When plotting, use sensible scales, label axes with variable and unit, and plot all points accurately. A sharp pencil and a clear ruler for any line of best fit are expected. If you plot the points incorrectly, you lose not only the plotting marks but also the interpretation mark.
作图时，要使用合理的比例，用变量和单位标注坐标轴，并准确绘制所有数据点。绘制最佳拟合线时需要使用削尖的铅笔和清晰的直尺。如果数据点画错，不仅会失去绘图分，还会失去解释分。
Sometimes the insert contains a column for 1/time because rate is proportional to 1/time when the endpoint is a fixed observable change. You should be able to explain this in terms of the constant amount of product required to obscure a cross or reach a set colour change.
有时插页中包含1/时间一列，因为当终点是一个固定的可见变化时，速率与1/时间成正比。你应该能够解释这一点：因为达到遮住十字或特定颜色变化所需的产物量是恒定的。
7. Evaluating Experimental Procedures from the Insert | 根据插页评价实验步骤
Evaluation questions often ask you to identify sources of error, suggest improvements, or comment on whether the data support a particular conclusion. The January 2019 insert gave specific data, so an evaluation answer that ignored the numbers was unlikely to reach the top mark.
评价题通常要求你找出误差来源、提出改进建议，或评论数据是否支持某一结论。2019年1月插页给出了具体数据，因此忽视数字的评价答案很难拿到最高分。
For example, if the results table shows times decreasing as temperature increases, you can say the rate increases with temperature. But a better evaluation might add: “The time at 50 °C is one-sixth of the time at 20 °C, which suggests a significant increase in rate, although the exact shape of the curve cannot be confirmed from only four data points.”
例如，如果结果表显示随着温度升高时间减少，你可以说速率随温度升高而增大。但更好的评价可能会补充：“50 °C时的时间是20 °C时的六分之一，这表明速率显著增大，不过仅凭四个数据点无法确认曲线的确切形状。”
Common limitations visible in inserts include small temperature ranges, few repeat readings, no blank titration, or lack of a preliminary trial to choose an appropriate concentration. When you evaluate, link the limitation to the data shown in the insert.
插页中常见的局限性包括温度范围较小、重复读数少、没有空白滴定，或没有先做初步实验来选择合适的浓度。评价时，要将局限性与插页中显示的数据联系起来。
8. Common Command Words in the January 2019 Unit 3 Paper | 2019年1月Unit 3试卷中的常见指令词
AQA uses command words carefully. “State” means a short answer from the insert or your knowledge. “Calculate” means show your method and give a numerical answer with units. “Suggest” means an answer based on evidence but not necessarily fully proved. “Evaluate” means give strengths and limitations, then a judgement.
AQA使用指令词非常严谨。”State”表示根据插页或所学知识给出简短回答。”Calculate”表示展示计算过程并给出带单位的数值答案。”Suggest”表示依据证据但未必完全被证实的答案。”Evaluate”表示给出优点和局限性，然后作出判断。
When you see “Use the data in the insert to calculate the percentage uncertainty”, you must quote numbers from the insert and put them into the formula. If you give a general explanation without numbers, you will not earn the calculation mark.
当你看到“使用插页中的数据计算百分比不确定度”时，必须引用插页中的数字并将其代入公式。只给出一般性说明而没有数字，将无法获得计算分。
9. Worked Example from a Typical Unit 3 Insert Question | 一道典型Unit 3插页题的示范解答
Suppose the January 2019 insert gave the following titre values for a titration: 24.25 cm³, 24.45 cm³, and 24.55 cm³. The question might ask: “Calculate the mean titre, and hence the concentration of the sodium hydroxide solution if 25.0 cm³ of it was titrated with 0.100 mol dm⁻³ hydrochloric acid.”
假设2019年1月插页给出以下滴定体积：24.25 cm³、24.45 cm³和24.55 cm³。题目可能问：“计算平均滴定体积，并因此计算与0.100 mol dm⁻³盐酸滴定的25.0 cm³氢氧化钠溶液的浓度。”
First, calculate the mean titre. The difference between the largest and smallest values is 0.30 cm³, which is within the usual tolerance, so all three can be averaged:
首先，计算平均滴定体积。最大值与最小值之差为0.30 cm³，在通常容差范围内，因此三个值都可以取平均：
Mean titre = (24.25 + 24.45 + 24.55) ÷ 3 = 24.416… ≈ 24.42 cm³
Then convert to dm³ and work out the moles of HCl:
然后转换为dm³并计算HCl的摩尔数：
n(HCl) = 0.100 × (24.42 ÷ 1000) = 0.002442 mol
Use the 1:1 ratio and the volume of NaOH to find its concentration:
利用1:1的比例和NaOH的体积求其浓度：
c(NaOH) = 0.002442 ÷ (25.0 ÷ 1000) = 0.0977 mol dm⁻³
Finally, round your answer to an appropriate number of significant figures. The values given suggest three significant figures, so 0.0977 mol dm⁻³ is acceptable.
最后，将答案修约到适当的有效数字位数。所给数据表明可以使用三位有效数字，因此0.0977 mol dm⁻³是可以接受的。
10. Common Mistakes When Using the Insert | 使用插页时的常见错误
One common mistake is copying values from the wrong row or column. If the question asks for the time at 30 °C and the table lists 1/time as well, some candidates accidentally use the derived column rather than the raw time. Underline the heading and unit before you select a value.
一个常见错误是抄错行或列的数据。如果题目要求30 °C下的时间，而表格中也列出了1/时间，有些考生会误用推导列而不是原始时间。选择数值前，先划出标题和单位。
Another frequent error is failing to convert cm³ to dm³. The unit “mol dm⁻³” only works if the volume is in dm³. If the question gives a volume in cm³, divide by 1000 before multiplying by the concentration.
另一个常见错误是没有将cm³转换为dm³。只有当体积单位为dm³时，单位“mol dm⁻³”才成立。如果题目给出的体积单位是cm³，在乘以浓度之前要先除以1000。
Finally, many candidates ignore the significant figures instruction. If the insert values have three significant figures, your final answer should not have six. Rounding to the correct number of significant figures shows you understand the precision of the data.
最后，许多考生忽略有效数字要求。如果插页中的数值有三位有效数字，你的最终答案不应有六位。修约到正确的有效数字位数表明你理解数据的精密度。
11. Using the Insert Efficiently During the Exam | 在考试中高效使用插页
Start by reading the title and aim of the experiment given in the insert. Then scan the table headings and units. Only after that should you read the first
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