📚 KS3 Edexcel Science: Case Study Practice | KS3 Edexcel 科学：案例分析实战演练
Case studies are at the heart of the KS3 Edexcel Science course, helping you connect classroom theory with practical investigations. In this article, we will work through a realistic case study on plant growth, uncovering how to collect data, spot patterns, and critique the experiment like a real scientist. By the end, you will feel confident tackling any case study question.
案例研究是 KS3 Edexcel 科学课程的核心，帮助你将课堂理论与实际调查联系起来。在本文中，我们将演练一个关于植物生长的真实案例研究，揭示如何收集数据、发现规律，并像真正的科学家一样批判实验。学完后，你将自信地应对任何案例分析题。
1. Understanding Scientific Case Studies | 理解科学案例研究
A scientific case study involves planning an investigation, collecting data, and interpreting results. You must identify variables, spot patterns, and critically assess the reliability of the evidence. This mirrors how scientists work in the real world.
科学案例研究包括规划调查、收集数据和解释结果。你必须识别变量、发现规律，并批判性地评估证据的可靠性。这反映了科学家在真实世界中的工作方式。
2. Case Study Background: Light and Plant Growth | 案例背景：光照与植物生长
Plants need light for photosynthesis, the process that produces food and energy for growth. The intensity of light can affect how quickly a plant grows. In this case study, a student named Jack wants to find out how different light intensities affect the height of mung bean seedlings.
植物需要光进行光合作用，这个过程为生长制造食物和能量。光照强度会影响植物生长的速度。在本案例中，一位名叫杰克的学生想探究不同光照强度如何影响绿豆幼苗的高度。
3. The Investigation Design | 调查设计
Jack set up three groups of mung bean seeds, each containing 10 seeds. He placed them under different light conditions: low light (20 lux), medium light (200 lux), and high light (2000 lux). He kept all other conditions the same: the same type of soil, the same amount of water, and a constant temperature of 20 °C. After 7 days, he measured the height of each seedling in centimetres.
杰克设置了三组绿豆种子，每组含 10 粒种子。他将它们置于不同光照条件下：低光（20 lux）、中光（200 lux）和高光（2000 lux）。他保持了所有其他条件相同：同样的土壤类型、同样的浇水量，以及恒温 20 °C。7 天后，他测量了每株幼苗的高度，单位为厘米。
4. Data Collection and Presentation | 数据收集与展示
The table below shows the raw data and calculated means. Note the anomalous result in the high light group, marked with an asterisk.
下表显示了原始数据和计算的平均值。注意高光组中的异常结果，已用星号标记。
| Light intensity (lux) | Trial 1 (cm) | Trial 2 (cm) | Trial 3 (cm) | Mean height (cm) |
| 20 | 5.0 | 5.4 | 5.2 | 5.2 |
| 200 | 8.5 | 8.8 | 8.7 | 8.7 |
| 2000 | 12.1 | 12.5 | 9.8* | 12.3 (excluding anomaly) |
Jack observed that the 9.8 cm reading in the high light group was much lower than the other two readings. He decided that this seedling may have been damaged and therefore removed it as an anomaly before calculating the true mean.
杰克观察到高光组中 9.8 cm 的读数远低于其他两个读数。他认为这株幼苗可能受损，因此将其作为异常值剔除，然后再计算真实平均值。
5. Identifying Variables | 识别变量
In any case study, it is crucial to identify the independent, dependent, and control variables. For Jack's experiment:
在任何案例研究中，识别自变量、因变量和控制变量至关重要。对于杰克的实验：
- Independent variable: light intensity (the one he changed).
自变量：光照强度（他改变的量）。 - Dependent variable: seedling height (the one he measured).
因变量：幼苗高度（他测量的量）。 - Control variables: temperature, volume of water, soil type, number of seeds, and growth period (these must stay the same to ensure a fair test).
控制变量：温度、浇水量、土壤类型、种子数量和生长周期（这些必须保持不变以确保公平测试）。
6. Calculating Averages and Dealing with Anomalies | 计算平均值和处理异常值
.8 cm was excluded because it fell far outside the expected range. The new mean was (12.1 + 12.5) ÷ 2 = 12.3 cm. Always state if you have removed an anomaly and give a reason.
计算平均值有助于消除随机差异。对于低光组：(5.0 + 5.4 + 5.2) ÷ 3 = 5.2 cm。在高光组，可疑的 9.8 cm 被排除，因为它远超出预期范围。新平均值为 (12.1 + 12.5) ÷ 2 = 12.3 cm。如果你剔除了异常值，务必说明并给出理由。
7. Drawing and Interpreting a Bar Chart | 绘制并解读条形图
To visualise the results, Jack drew a bar chart with light intensity on the x-axis (low, medium, high) and mean height on the y-axis. Each bar must be of equal width, neatly spaced, and properly labelled. He added the title 'The Effect of Light Intensity on Mung Bean Seedling Height.'
为了直观展示结果，杰克绘制了条形图，x 轴为光照强度（低、中、高），y 轴为平均高度。每个条形必须等宽、间距均匀，并正确标注。他加上了标题 '光照强度对绿豆幼苗高度的影响'。
From the chart, the pattern is clear: as light intensity increases, the mean seedling height also increases. The bar for 2000 lux is much taller than the bar for 20 lux. This suggests a positive correlation within the tested range.
从图表可以清楚看出规律：随着光照强度增加，幼苗的平均高度也增加。2000 lux 所对应的条形明显高于 20 lux 的条形。这表明在测试范围内存在正相关。
8. Writing a Conclusion | 撰写结论
Jack's conclusion: 'The higher the light intensity, the taller the mung bean seedlings grew. The mean height increased from 5.2 cm at 20 lux to 12.3 cm at 2000 lux. This supports the idea that more light allows more photosynthesis, leading to faster growth.' A good conclusion refers back to the data and uses scientific reasoning.
杰克的结论：'光照强度越高，绿豆幼苗长得越高。平均高度从 20 lux 时的 5.2 cm 增加到 2000 lux 时的 12.3 cm。这支持了这样的观点：更多的光允许更多的光合作用，从而加快生长。' 一个好的结论需要引用数据并运用科学推理。
9. Evaluating the Method | 评估方法
No experiment is perfect. Jack identified strengths and areas for improvement:
没有完美的实验。杰克识别了优点和需要改进的方面：
- Strengths: he used three trials per light level and controlled key variables like temperature and water.
优点：每个光照水平使用了三次重复，并控制了温度和水分等关键变量。 - Weakness 1: only three seedlings were measured per group (after excluding anomalies) – a larger sample size would give more reliable means.
弱点1：每组仅测量了三株幼苗（剔除异常后）——更大的样本量会得到更可靠的平均值。 - Weakness 2: he only recorded height. Measuring leaf number or dry mass could give a fuller picture of growth.
弱点2：他只记录了高度。测量叶片数量或干质量能更全面地反映生长。 - Weakness 3: the high light lamp might have produced extra heat, affecting the temperature control despite his efforts.
弱点3：高光灯可能产生额外热量，尽管他努力控制，温度仍可能受到影响。
To improve, Jack could use a heat filter, increase the number of seeds, and add more light intensity levels (e.g. 100 lux, 500 lux) to see a finer trend.
为了改进，杰克可以使用隔热滤镜、增加种子数量，并增加更多的光照强度级别（如 100 lux、500 lux），以观察更精细的趋势。
10. Common Mistakes in Case Studies | 案例分析中的常见错误
When you solve case studies, watch out for these typical pitfalls:
当你解决案例研究时，要小心这些常见的陷阱：
- Confusing the independent and dependent variables – always ask "which is changed?" and "which is measured?"
混淆自变量和因变量——总是问'哪个被改变？'和'哪个被测量？'。 - Including an anomalous result without checking – always look for odd readings and decide whether to exclude them with justification.
未经检查就纳入异常结果——始终寻找异常读数，并决定是否排除它们并给出理由。 - Drawing bars that touch or are not equally spaced on a bar chart – a bar chart for categories (like low, medium, high) must have gaps.
条形图的条形相互接触或间距不等——类别的条形图（如低、中、高）必须有间隙。 - Writing a conclusion that does not link back to the data – always state exact figures to support your claim.
写结论时未关联数据——始终陈述确切数字来支持你的主张。
11. Practice Question for You | 给你一道练习题
Now it is your turn. A student investigated how different concentrations of fertilizer affect the number of flowers on marigold plants. She used three concentrations: 0 g/L, 2 g/L, and 4 g/L. She repeated each concentration three times and counted flowers after 6 weeks. Her results: 0 g/L – 5, 6, 4; 2 g/L – 8, 9, 7; 4 g/L – 12, 15, 13.
现在轮到你了。一位学生研究了不同肥料浓度如何影响万寿菊植株的花朵数量。她使用了三种浓度：0 g/L、2 g/L 和 4 g/L。每个浓度重复三次，6 周后计数花朵。她的结果：0 g/L——5, 6, 4；2 g/L——8, 9, 7；4 g/L——12, 15, 13。
Calculate the mean number of flowers for each concentration. Identify the independent and dependent variables. Then write a short conclusion linking the data to a scientific explanation (hint: fertilizers contain minerals like nitrates that help plants grow).
计算每种浓度的平均花朵数量。识别自变量和因变量。然后写一个简短的结论，将数据与科学解释联系起来（提示：肥料含有硝酸盐等矿物质，有助于植物生长）。
12. Final Tips and Summary | 最终提示与总结
Case studies in KS3 Science are excellent practice for thinking methodically. Always begin by underlining the key question, list your variables, and handle data with care. When evaluating, balance strengths with honest criticisms. With regular practice, you will ace your Edexcel assessments.
KS3 科学中的案例研究是系统性思维的绝佳练习。一开始要划出关键问题，列出变量，并小心处理数据。评估时要平衡优点与诚实的批评。通过定期练习，你将在 Edexcel 评估中取得优异成绩。
Published by TutorHao | Science Revision Series | aleveler.com
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