A-Level Biology: Describing Experimental Procedure Order | A-Level 生物：实验步骤顺序的描述方法

📚 A-Level Biology: Describing Experimental Procedure Order | A-Level 生物：实验步骤顺序的描述方法

In A-Level Biology, exam questions often ask you to describe the order of experimental steps. This requires more than just memorising a protocol; it demands clear, logical, and precise scientific writing. You must show the examiner that you understand not only what to do, but also why each step is done at that particular point in the procedure.

在 A-Level 生物考试中，题目经常要求你描述实验步骤的顺序。这不仅需要记住实验流程，更要求你以清晰、有逻辑且精确的科学语言进行表达。你需要向考官展示，你不仅知道每一步要做什么，还理解为什么每一步要在实验程序的特定节点完成。

1. The Importance of Chronological Logic | 时间顺序逻辑的重要性

Experimental procedures in biology are never random. Each step is placed at a specific point for a reason: to avoid contamination, to allow reactions to occur, to ensure accurate measurement, or to maintain the validity of the control variables. When describing procedure order, your first task is to recognise the underlying logic of the sequence.

生物学中的实验步骤绝不是随意的。每一步都被安排在特定的位置，其原因可能是避免污染、让反应充分发生、确保测量准确，或是维持控制变量的有效性。在描述步骤顺序时，你的首要任务是识别实验序列背后的逻辑。

Identify the aim and the independent variable first. The procedure must change the independent variable while keeping all else constant.

首先明确实验目的和自变量。实验步骤必须改变自变量，同时保持其他条件恒定。
Recognise the sequence pattern: preparation → treatment → measurement → analysis.

识别基本顺序模式：准备 → 处理 → 测量 → 分析。
Look for cause-and-effect links: step A creates the condition needed for step B.

寻找因果关系链：步骤 A 为步骤 B 创造了所需要的条件。

2. Key Transition Words and Phrases | 关键过渡词与短语

In describing procedure order, you must use sequence markers clearly. In English, words such as ‘firstly’, ‘then’, ‘next’, ‘after that’, ‘subsequently’, ‘finally’ are essential. In Chinese, you would use ‘首先’、’然后’、’接着’、’之后’、’最后’. These transitions help the examiner follow the order without confusion.

在描述实验步骤顺序时，必须清晰使用顺序标记词。在英文中，firstly、then、next、after that、subsequently、finally 等词必不可少。在中文中，则使用’首先’、’然后’、’接着’、’之后’、’最后’。这些过渡词能帮助考官毫无困惑地跟随操作顺序。

Firstly → Then → Next → After that → Subsequently → Finally

首先 → 然后 → 接着 → 之后 → 随后 → 最后

You should also use ‘before’ and ‘after’ to show relative timing. For example, ‘Before adding the enzyme, the substrate solution was equilibrated to 37°C.’

你还应使用 before 和 after 来表达相对时间顺序。例如：’在加入酶之前，底物溶液已在 37°C 下平衡。’

3. Using Active and Passive Voice Correctly | 正确使用主动语态与被动语态

In scientific writing, both active and passive voice are used. The passive voice (‘the solution was heated’) is common in formal biology reports because it emphasises the action rather than the person performing it. However, when the identity of the experimenter is relevant, the active voice may be used.

在科学写作中，主动语态和被动语态都会用到。被动语态（’the solution was heated’ 溶液被加热）在正式生物学报告中很常见，因为它强调的是动作本身而非操作者。然而，当操作者的身份重要时，也可以使用主动语态。

Passive voice: ‘The sample was centrifuged at 4000 × g for 5 minutes.’

被动语态：’样品在 4000 × g 下离心 5 分钟。’
Active voice: ‘We measured the absorbance immediately.’

主动语态：’我们立即测量了吸光度。’

In exam answers, it is often safer to use the passive voice in English because it sounds more objective and scientific. In Chinese, use ‘将……’、’……被……’ structures appropriately.

在考试作答中，英文建议使用被动语态，因为它听起来更客观、更科学。在中文中，适当使用’将……置于……’、’……被……’等结构。

4. Describing Preparation Steps | 描述准备步骤

Before the main experiment begins, there are usually several preparation steps: cleaning equipment, preparing solutions, setting up the apparatus, and labelling containers. These must be described in the correct order because, for example, you cannot dilute a solution before you have measured the stock solution.

在主实验开始之前，通常有若干个准备步骤：清洗仪器、配制溶液、搭建装置、标记容器。这些步骤必须按正确顺序描述，例如，你不能在量取原液之前就稀释溶液。

State the equipment first: ‘A clean test tube was rinsed with distilled water.’

先说明器材：’用蒸馏水润洗干净的试管。’
Then describe the solution preparation: ‘2 cm³ of 1% starch solution was measured using a pipette.’

然后描述溶液配制：’用移液管量取 2 cm³ 的 1% 淀粉溶液。’
Finally describe the setup: ‘The tube was placed in a water bath at 30°C for 5 minutes to equilibrate.’

最后描述装置搭建：’将试管置于 30°C 水浴中 5 分钟以达到平衡。’

5. Describing the ‘Treatment’ Stage | 描述’处理’阶段

The treatment stage is where the independent variable is applied. This is often the heart of the experiment. When describing this stage, you must specify the exact quantity, concentration, volume, time, temperature, and the order of adding reagents.

处理阶段是施加自变量的阶段。这通常是实验的核心。在描述这一阶段时，你必须精确说明数量、浓度、体积、时间、温度以及添加试剂的顺序。

Independent variable → Treatment applied → Reaction allowed → Stopped

自变量 → 施加处理 → 让反应进行 → 终止反应

For example, in an enzyme experiment, you might write: ‘The enzyme solution was added to the substrate and the mixture was incubated at 35°C. After exactly 3 minutes, the reaction was stopped by adding 1 cm³ of hydrochloric acid.’

例如，在酶实验中，你可以这样写：’将酶液加入底物中，混合物在 35°C 下保温。恰好 3 分钟后，加入 1 cm³ 盐酸终止反应。’

Note the importance of ‘exactly’ and ‘by adding’ – these show precision and method.

注意’exactly（恰好）’和’by adding（通过加入）’的重要性——这些词体现了精确性和操作方法。

6. Describing Measurement and Recording | 描述测量与记录

After the treatment, the experimenter measures the outcome. In biology, measurements may be taken using a colorimeter, microscope, balance, or timing device. The description must state what was measured, the instrument used, and the units recorded.

处理之后，实验者需要测量结果。在生物学中，测量可能使用比色计、显微镜、天平或计时器等设备。描述必须说明测量什么、使用什么仪器以及记录什么单位。

‘The absorbance was read at 540 nm using a colorimeter.’

‘使用比色计在 540 nm 波长处读取吸光度。’
‘The number of bubbles was counted over a 1-minute period.’

‘在 1 分钟内计数气泡数量。’
‘The mass of the potato cylinder was recorded using a digital balance to the nearest 0.01 g.’

‘用数字天平记录马铃薯条的质量，精确至 0.01 g。’

When repeating measurements, say so: ‘This was repeated three times and the mean was calculated.’ Repetition is critical in biology for reliability.

如果进行了重复测量，必须写明：’此操作重复三次并计算平均值。’ 重复在生物学中对于可靠性至关重要。

7. Describing Controls and Safety Steps | 描述对照组与安全步骤

A well-designed experiment always includes a control. When describing procedure order, you must explain where the control is set up – usually alongside the experimental group, not after it. For example, in a photosynthesis experiment, the control might be a foil-wrapped test tube to block light.

一个设计良好的实验总是包含对照组。在描述实验步骤顺序时，你必须说明对照组在哪里设置——通常是与实验组同时设置，而不是在其之后。例如，在光合作用实验中，对照组可能是一个用锡纸包裹以遮光的试管。

Safety steps also appear in the procedure sequence. They are placed before the dangerous step, not during or after. For example: ‘Before heating, safety goggles were worn and the Bunsen burner was checked for leaks.’

安全步骤也出现在实验程序中。它们被安排在危险步骤之前，而不是之中或之后。例如：’加热前，戴上护目镜并检查本生灯是否漏气。’

8. Common Mistakes in Describing Order | 描述顺序的常见错误

Many students lose marks not because they do not know the experiment, but because their description of the order is flawed. Below are common mistakes and how to avoid them.

许多学生丢分不是因为不知道实验，而是因为对顺序的描述有缺陷。以下是常见错误及避免方法。

Mistake / 错误	Why it is wrong / 为什么错误	Correction / 修正
Adding reagent before measuring it	Volume or concentration becomes inaccurate	Measure first, then add
Mixing and then heating without equilibration	The reaction starts before the intended temperature is reached	Equilibrate the substrate first, then add enzyme
Forgetting to stop the reaction at a fixed time	Timing error affects all data sets	State the timing and use a stop-clock
Describing the control after the experimental group	Suggests the control is an afterthought; not rigorous	Describe control and experimental groups together

Always ask yourself: ‘Does my description allow another student to repeat the experiment exactly?’ If yes, your order description is likely correct.

始终问自己：’我的描述是否能让另一个学生完全重复这个实验？’ 如果能，那么你的顺序描述很可能是正确的。

9. Using ‘Before’ and ‘After’ in Complex Sequences | 在复杂流程中使用’之前’与’之后’

Some biological experiments involve parallel procedures or branching steps. For example, in a DNA extraction experiment, you may perform the extraction and the preparation of the buffer solution simultaneously. In such cases, use ‘meanwhile’ or ‘at the same time’.

有些生物学实验涉及平行步骤或分支流程。例如，在 DNA 提取实验中，你可能同时进行 DNA 提取和缓冲液的配制。在这种情况下，可以使用’meanwhile（与此同时）’或’at the same time（同时）’。

Example: ‘The sample was ground in a mortar with sand. Meanwhile, a water bath was heated to 60°C.’ This clearly shows two actions happening in parallel.

示例：’在研钵中加入沙子研磨样品。与此同时，水浴加热至 60°C。’ 这清楚地表明两个操作同时进行。

For serial steps, use ‘before’ to link: ‘The pellet was washed with buffer before being resuspended.’

对于连续步骤，用 before 连接：’沉淀先用缓冲液洗涤，然后重悬。’

10. Describing the Repeats and Reliability | 描述重复操作与可靠性

In the final stages of a procedure, you usually repeat measurements and calculate a mean. You must describe this as part of the order: first collect raw data, then repeat, then calculate the mean and standard deviation.

在实验流程的最后阶段，你通常会重复测量并计算平均值。你必须将其描述为顺序的一部分：先收集原始数据，然后重复，最后计算平均值和标准差。

Collect raw data → Repeat → Calculate mean → Calculate SD → Plot graph

收集原始数据 → 重复 → 计算平均值 → 计算标准差 → 绘制图表

An examiner-friendly way to describe this is: ‘The experiment was repeated five times for each concentration. The mean value and standard deviation were calculated and presented as error bars on the graph.’

一种讨考官喜欢的方式是：’每个浓度下的实验重复五次。计算平均值和标准差，并以误差线的形式在图表上呈现。’

11. Mark Scheme Keywords | 评分标准关键词

When describing experimental procedure order, certain keywords appear frequently in CIE mark schemes. Using them increases your chances of scoring full marks.

在描述实验步骤顺序时，某些关键词会频繁出现在 CIE 评分标准中。使用它们能提高你获得满分的机会。

Equilibrate / 平衡 – ‘The solution was equilibrated to 30°C.’

平衡 – ‘将溶液在 30°C 下平衡。’
Incubate / 保温 – ‘The mixture was incubated for 20 minutes.’

保温 – ‘将混合物保温 20 分钟。’
Centrifuge / 离心 – ‘The sample was centrifuged to separate the pellet.’

离心 – ‘离心样品以分离沉淀。’
Rinse / 润洗 – ‘The pipette was rinsed with the solution before use.’

润洗 – ‘使用前用待取溶液润洗移液管。’
Stop / 终止 – ‘The reaction was stopped by heating at 100°C.’

终止 – ‘通过 100°C 加热终止反应。’
Repeat / 重复 – ‘The procedure was repeated to improve reliability.’

重复 – ‘重复该过程以提高可靠性。’

12. Worked Example: Enzyme Temperature Experiment | 例题：酶温度实验

Let us now apply all of this to a classic CIE practical question: ‘Describe how you would carry out an experiment to investigate the effect of temperature on the rate of amylase activity.’ Here is a model answer showing correct order description.

现在，我们将以上所有内容应用到一个经典的 CIE 实验题中：’描述你如何设计实验来探究温度对淀粉酶活性的影响。’ 以下是一个展示正确顺序描述的模型答案。

Answer (English): ‘First, five test tubes were labelled 10°C, 20°C, 30°C, 40°C, and 50°C. Then, 2 cm³ of 1% starch solution was added to each tube. Next, each tube was placed in a water bath at its labelled temperature and left for 3 minutes to equilibrate. Meanwhile, five separate tubes each containing 1 cm³ of amylase solution were placed in the same water baths. After equilibration, the amylase was added to the corresponding starch tubes and the stopwatch was started immediately. After exactly 5 minutes, one drop of the mixture was removed and tested with iodine solution. When the iodine remained yellow-brown, the starch had been fully digested. This was repeated for all tubes and the time for complete digestion was recorded for each temperature.’

答案（中文）：’首先，给五支试管分别标记 10°C、20°C、30°C、40°C 和 50°C。然后，向每支试管中加入 2 cm³ 的 1% 淀粉溶液。接着，将每支试管放入对应温度的水浴中，静置 3 分钟以平衡温度。与此同时，另外五支试管分别加入 1 cm³ 淀粉酶溶液，也放入相同的水浴中。平衡后，将淀粉酶加入对应的淀粉试管中，并立即启动秒表。恰好 5 分钟后，取出一滴混合液，用碘液检测。当碘液保持黄棕色时，说明淀粉已完全水解。对所有试管重复此操作，并记录每个温度下完全消化所需的时间。’

Notice the order markers: first, then, next, meanwhile, after, immediately, exactly, for all tubes. This is a model description of experimental procedure order.

请注意顺序标记词：首先、然后、接着、与此同时、之后、立即、恰好、对所有试管。这就是实验步骤顺序描述的典范。

Conclusion | 结语

Describing experimental procedure order in A-Level Biology requires a systematic approach: understand the aim, identify the sequence, use clear transition words, employ the correct voice, and include exact quantities and timings. By mastering these skills, you will not only achieve higher marks in exam questions but also become a more capable scientist.

在 A-Level 生物学中描述实验步骤顺序需要系统化的方法：理解实验目的、识别顺序、使用清晰的过渡词、采用正确的语态，并包含精确的数量和计时。掌握这些技能后，你不仅能在考试中获得更高分数，还能成为一个更有能力的科学工作者。

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A-Level Biology: Describing Experimental Procedure Order | A-Level 生物：实验步骤顺序的描述方法