📚 Year 7 OCR Science: Case Study Practice | Year 7 OCR 科学案例分析实战演练
In Year 7 OCR Science, case studies give you the chance to see how scientific ideas work in the real world. A case study is not just a story — it is a set of observations, data tables, graphs and experimental details that you need to read carefully, analyse and evaluate. This skill helps you think like a scientist and prepares you for practical investigations and examinations. In this article you will explore what scientific case studies are, how to interpret variables and data, and how to draw sensible conclusions. You will also work through two complete case study examples to practise all the key steps.
在Year 7 OCR科学中，案例研究让你有机会看到科学思想如何在现实世界中发挥作用。一个案例研究不仅仅是一个故事——它是一组观察结果、数据表、图表和实验细节，你需要仔细阅读、分析和评估。这项技能帮助你像科学家一样思考，并为实践调查和考试做好准备。在这篇文章中，你将探索什么是科学案例研究，如何解释变量和数据，以及如何得出合理的结论。你还会演练两个完整的案例研究实例，来练习所有关键步骤。
1. What Is a Scientific Case Study? | 什么是科学案例研究？
A scientific case study presents a real or realistic investigation in a structured way. It usually starts with a question, describes the method used, and provides the results in the form of numerical data, observations or both. In Year 7 OCR Science, you might see a case study about the effect of light on plant growth, the pH of household substances, or the speed of a falling object. Your job is to examine the information, spot patterns, link them to your science knowledge and decide how reliable the conclusions are.
科学案例研究以结构化的方式呈现一项真实或逼真的调查。它通常以一个问题开始，描述所使用的方法，并以数值数据、观察结果或两者的形式提供结果。在Year 7 OCR科学中，你可能会看到关于光照对植物生长的影响、家用物质的pH值或下落物体速度的案例研究。你的任务是检查这些信息，发现模式，将它们与你的科学知识联系起来，并判断这些结论有多可靠。
Good case studies often include tables with headings and units, printed graphs, and sometimes a short account of what went wrong during the experiment. You need to pay attention to every detail. For example, if a table shows temperature readings over time, but one reading is missing, you should notice that gap — it might affect the overall conclusion. Recognising those small features is part of being a careful scientist.
好的案例研究通常包括带表头和单位的数据表、打印好的图表，有时还有一段关于实验中出了什么问题的简短描述。你需要关注每一个细节。例如，如果一个表格显示了温度随时间变化的读数，但有一个读数缺失，你应该注意到那个空缺——它可能会影响整体结论。识别这些细微特征是成为一位细心的科学家的一部分。
2. Understanding Variables | 理解变量
Every experiment has variables — things that can change. In Year 7 OCR Science, you are expected to identify three kinds: independent variable (the one you deliberately change), dependent variable (the one you measure or observe), and control variables (the ones you keep the same to make the test fair). If you misidentify any of these, your analysis of a case study will go off track very quickly.
每个实验都有变量——可以变化的东西。在Year 7 OCR科学中，你需要识别三种变量：自变量（你故意改变的那个）、因变量（你测量或观察的那个）和受控变量（你保持不变的变量，以确保测试公平）。如果你错误识别了其中任何一个，你对案例研究的分析会很快偏离方向。
Imagine a case study about how the length of a wire affects the brightness of a bulb. The independent variable is the length of the wire. The dependent variable is the brightness, which could be measured by a sensor or judged by eye. Control variables might include the type of wire, the battery voltage and the room temperature. When you read a case study, underline these variables in the text before you do anything else — it makes the rest of the analysis much easier.
设想一个关于导线长度如何影响灯泡亮度的案例研究。自变量是导线的长度。因变量是亮度，可以用传感器测量或肉眼判断。受控变量可能包括导线的类型、电池电压和室温。当你阅读一个案例研究时，在做其他事情之前，先在这些变量下面划线——这会让接下来的分析变得容易得多。
3. Identifying Hypothesis and Predictions | 识别假设与预测
A hypothesis is a suggested scientific explanation that you can test. A prediction is a statement about what you think will happen in your experiment if the hypothesis is correct. For example, if your hypothesis is ‘more light energy makes plants grow faster’, your prediction might be ‘the plants that receive 12 hours of light per day will grow taller than those that receive 6 hours’. In a case study, the hypothesis and prediction might be given clearly, or you might need to infer them from the method and results.
假设是你可以检验的一种科学解释提议。预测是关于如果假设正确，你认为在实验中会发生什么的陈述。例如，如果你的假设是 “更多的光能使植物生长更快”，你的预测可能是 “每天接受12小时光照的植物会比那些接受6小时光照的植物长得更高”。在案例研究中，假设和预测可能会被明确给出，或者你可能需要从方法和结果中推断它们。
Many students confuse a hypothesis with a random guess. A hypothesis must be based on prior knowledge. When you analyse a case study, ask yourself: does the conclusion support or refute the hypothesis? If the data contradicts the hypothesis, the scientist should then suggest a new, improved hypothesis — that is how real science works, and you may be asked about this in your OCR assessment.
许多学生把假设和随意猜测混为一谈。假设必须基于先前的知识。当你分析一个案例研究时，问自己：结论支持还是反驳了假设？如果数据与假设相矛盾，那么科学家就应该提出一个新的、改进的假设——这就是真实科学的运作方式，在OCR考核中你可能会被问到这一点。
4. Collecting and Recording Data | 收集与记录数据
Accurate data collection is the backbone of any case study. Data can be qualitative (describes qualities, like colour or smell) or quantitative (involves numbers and units). In Year 7 OCR Science, you are often asked to suggest improvements to the way data was recorded. Look out for whether the experimenter repeated measurements, how the readings were displayed, and whether any results seem unusual (these are called anomalies).
准确的数据收集是任何案例研究的支柱。数据可以是定性的（描述性质，如颜色或气味）或定量的（涉及数字和单位）。在Year 7 OCR科学中，你经常会被要求对数据记录的方式提出改进建议。注意实验者是否重复了测量，读数是如何呈现的，以及是否有任何结果看起来异常（这些被称为异常值）。
A case study might tell you: ‘The temperature of the water was measured every minute for 10 minutes, but the thermometer was read only to the nearest degree.’ That level of precision might not be enough. Recording to one decimal place using a digital thermometer would give more reliable data. When you answer a question, you can suggest using a more precise instrument or taking more frequent readings — but always give a reason linked to better evidence.
一个案例研究可能会告诉你：”水温每隔一分钟测量一次，共10分钟，但温度计只读取到最接近的度数。”那种精确度可能不够。使用数字温度计记录到一位小数会给出更可靠的数据。当你回答一个问题时，你可以建议使用更精确的仪器或更频繁地读数——但始终要给出与更好证据相关的理由。
5. Using Tables to Organise Data | 用表格组织数据
Tables make it easy to see raw data at a glance. A well-designed table has clear headings, units in the header row (not repeated in every cell), and a logical order. For a Year 7 case study, you should practise reading tables as well as constructing them. Never forget to include a title that explains what the table is showing.
表格使原始数据一目了然。一份设计良好的表格有清晰的表头，单位出现在标题行（而不是每个单元格中都重复），并且排列合乎逻辑。对于Year 7的案例研究，你应该练习阅读表格以及构建表格。永远不要忘记包含一个解释表格内容的标题。
Here is an example table from a case study about plant growth under different coloured lights:
这里有一个来自关于不同颜色光照下植物生长案例研究的示例表格：
| Light colour | Initial height (cm) | Final height after 7 days (cm) | Growth (cm) |
|---|---|---|---|
| Red | 5.0 | 8.5 | 3.5 |
| Blue | 5.1 | 9.7 | 4.6 |
| Green | 4.9 | 6.3 | 1.4 |
| White | 5.0 | 8.8 | 3.8 |
Notice how the units appear only in the header row and every column is labelled. Always check that the numerical values are recorded consistently. If one measurement is missing, the data might not be completely trustworthy.
注意单位仅出现在标题行，并且每一列都有标签。始终检查数值是否被一致地记录。如果某个测量值缺失，数据可能不完全可信。
6. Drawing Graphs and Charts | 绘制图表
Once you have a data table, the next step is often to draw a graph. In OCR Year 7 Science, you need to know when to use a bar chart and when to use a line graph. A bar chart is for comparing categories — for example, the colours of light in the table above. A line graph is usually used when the independent variable is continuous, such as time or temperature, because it shows a trend.
一旦你有了数据表，下一步往往是绘制图表。在OCR Year 7科学中，你需要知道何时使用条形图、何时使用折线图。条形图用于比较类别——例如上面表格中光线的颜色。折线图通常在自变量是连续的时候使用，比如时间或温度，因为它能显示趋势。
A good graph includes a title, labelled axes with units, a sensible scale and accurately plotted points. If a case study shows you a graph with a missing axis label or an awkward scale, you can criticise it. Even the ‘choose a line of best fit’ question in a case study tests your ability to ignore anomalous points and draw a smooth line through the remaining points.
一张好的图表包含标题、带单位的坐标轴标签、合理的刻度和准确描点。如果案例研究给你展示了一个缺少轴标签或刻度不当的图表，你可以批评它。案例研究中甚至“选择最佳拟合线”的问题，也在测试你忽略异常点并穿过剩余点绘制光滑曲线的能力。
7. Interpreting Trends and Patterns | 解读趋势与模式
Interpreting data means describing what the numbers or graph lines actually show. Use phrases such as ‘as the temperature increases, the reaction time decreases’ or ‘the growth of the plant increased steadily between day 2 and day 5’. Avoid jumping to ‘why’ until you have described the ‘what’. In Year 7 OCR case studies, you score marks for accurate description before you move on to explanation.
解读数据意味着描述数字或图线实际展示了什么。使用诸如“随着温度升高，反应时间减少”或“植物的生长在第2天到第5天之间稳步增加”这样的短语。在描述“为什么”之前，避免过早跳到“为什么”。在Year 7 OCR案例研究中，你在转向解释之前，准确的描述会为你赢得分数。
A pattern might be a direct relationship (both variables increase together) or an inverse relationship (one increases while the other decreases). Sometimes there is a plateau, where the line flattens, suggesting a limit has been reached. When you see an unexpected spike or dip, pause and consider whether it is an anomaly. State clearly ‘this point does not fit the overall pattern, so it may be anomalous’.
一个模式可能是一种正比关系（两个变量一起增加）或反比关系（一个增加而另一个减少）。有时会出现平台，即线条变平，表明已经达到极限。当你看到一个意外的尖峰或低谷时，停下来想一想它是不是异常值。清楚地说明“这个点不符合总体模式，因此可能是异常值”。
8. Evaluating Evidence and Drawing Conclusions | 评估证据与得出结论
A conclusion must be directly supported by the data. For example, ‘the results support the hypothesis that salt dissolves faster in warm water because the data show that at 40 °C the dissolving time was 30 seconds shorter than at 20 °C’. Do not add information that is not in the case study. Evaluation is about judging the quality of the evidence: was the method described clearly? Were enough repeats taken? Could someone else follow the method exactly?
结论必须得到数据的直接支持。例如，“结果支持盐在温水中溶解更快的假设，因为数据显示在40 °C时溶解时间比20 °C时短了30秒”。不要添加案例研究中没有的信息。评估是关于判断证据质量的：方法描述清楚吗？有足够的重复实验吗？别人能完全按照这个方法操作吗？
In OCR assessments, you might be asked to suggest two improvements to the experiment. Common improvements include: using a more precise measuring instrument, controlling a variable that was not kept constant, or increasing the number of trials to calculate a reliable mean. Always explain how the improvement would make the evidence stronger.
在OCR考核中，你可能会被要求为实验提出两个改进建议。常见的改进建议包括：使用更精确的测量仪器，控制一个之前没有保持不变的变量，或者增加试验次数以计算可靠的平均值。永远要解释这一改进如何使证据更有力。
9. Practical Example 1: Investigating Plant Growth | 实践案例1：探究植物生长
Let us work through a realistic Year 7 case study. Two students want to find out if adding fertiliser to soil makes bean plants grow taller. They plant ten bean seeds in identical pots, five with ordinary soil (Group A) and five with soil mixed with fertiliser (Group B). All pots receive the same amount of water and light. After 14 days they measure the height of each plant. The recorded mean heights are: Group A = 12.4 cm, Group B = 17.1 cm.
让我们演练一个真实的Year 7案例研究。两个学生想知道在土壤中添加肥料是否会让豆类植物长得更高。他们在相同的花盆里种下十颗豆种，五盆用普通土壤（A组），五盆用混合了肥料的土壤（B组）。所有的花盆都接受相同的水分和光照。14天后，他们测量每株植物的高度。记录的平均高度为：A组 = 12.4 cm，B组 = 17.1 cm。
Identify the independent variable (presence of fertiliser), the dependent variable (height of plant) and the control variables (type of seed, volume of water, light, pot size). The hypothesis is that fertiliser increases growth. The prediction might have been ‘Group B plants will be taller’. The data clearly support this; the difference of 4.7 cm is significant. However, an evaluator might ask: did the students measure five plants in each group? If so, they should also show the individual readings, not just the mean. Without raw data, we cannot check for anomalies. That would be a fair criticism in an exam answer.
找出自变量（有无肥料）、因变量（植物高度）和受控变量（种子类型、水量、光照、花盆大小）。假设是肥料能促进生长。预测可能是 “B组植物会更高”。数据清楚地支持了这一假设；4.7 cm的差异是显著的。然而，评估者可能会问：学生们是否每组测量了五株植物？如果是，他们也应该展示各个读数，而不仅仅是平均值。没有原始数据，我们就无法检查异常值。在考试答案中，这会是合理的批评。
10. Practical Example 2: Testing the pH of Household Substances | 实践案例2：测试家用物质的pH值
A case study presents the following data collected by a student who used universal indicator solution to test five liquids:
一个案例研究呈现了某学生使用通用指示剂溶液测试五种液体所收集的以下数据：
| Substance | Colour with indicator | Estimated pH |
|---|---|---|
| Lemon juice | Red | 2 |
| Vinegar | Orange-red | 3 |
| Distilled water | Green | 7 |
| Bicarbonate of soda solution | Blue | 9 |
| Bleach | Purple | 13 |
The student concluded that all acids are coloured red and all alkalis are coloured purple. Is this conclusion fully justified? No — lemon juice (pH 2) and vinegar (pH 3) are both acids, but vinegar appeared orange-red, not pure red. Bleach is a strong alkali and turned purple, but bicarbonate of soda solution (pH 9) turned blue, showing that alkalis can give a range of colours. The correct conclusion is that the stronger the acid, the lower the pH and the more red the indicator; the stronger the alkali, the higher the pH and the more purple the indicator. This case study teaches you that a conclusion must match the evidence precisely.
该学生得出结论：所有的酸都呈红色，所有的碱都呈紫色。这个结论完全合理吗？不——柠檬汁（pH 2）和醋（pH 3）都是酸，但醋呈现橙红色，而不是纯红色。漂白剂是强碱，变成了紫色，但小苏打溶液（pH 9）变成了蓝色，表明碱可以呈现一系列颜色。正确的结论是：酸越强，pH值越低，指示剂越红；碱越强，pH值越高，指示剂越紫。这个案例研究教导你，结论必须与证据精确匹配。
To go further, you could write a balanced symbol equation to represent the neutralisation example hidden in the data, but you are not expected to invent one. Instead, note that the student did not measure pH with a probe, only estimated by colour. This is less accurate. A digital pH meter would provide precise values and strengthen the evidence. Always tie your evaluation back to the details of the case study.
更进一步，你可以写一个配平的符号方程式来表示隐藏在数据中的中和反应例子，但并不要求你凭空编造一个。相反，注意该学生没有用探针测量pH值，只是通过颜色来估计。这样精确度较低。数字pH计会提供精确值，并增强证据。一定要将你的评估与案例研究的具体细节联系起来。
11. Common Mistakes in Case Study Analysis | 案例分析常见错误
One common error is confusing the independent and dependent variables. For example, thinking that the height of a plant determines how much light it receives, rather than the other way around. Another is failing to criticise missing details — if the case study does not tell you how many repeats were done, point out that without repeats, the data could be unreliable. Many students also forget to mention specific control variables when asked to explain why a test was fair.
一个常见错误是混淆自变量和因变量。例如，认为是植物的高度决定了它接收到的光量，而不是反过来。另一个错误是未能批评缺失的细节——如果案例研究没有告诉你做了多少次重复实验，就要指出，没有重复实验，数据可能不可靠。许多学生在被要求解释测试为什么是公平时，也忘记提到具体的受控变量。
When interpreting graphs, students sometimes read the scale incorrectly or assume that a bar chart line can be connected as if it were a line graph — you cannot join bars on a bar chart! Also, avoid making conclusions go beyond the data. If a case study only tested plants up to 14 days, you cannot claim with certainty what would happen on day 20. Always qualify your conclusion with phrases like ‘based on the data presented’ or ‘within the range tested’.
在解读图表时，学生有时会错误地读取刻度，或者假定条形图的柱子可以像折线图一样连起来——你不能在条形图上连接柱子！此外，避免做出超越数据范围的结论。如果一个案例研究只测试了植物到第14天，你就不能肯定地声称第20天会发生什么。始终用“基于所呈现的数据”或“在测试范围内”这样的短语来限定你的结论。
12. Tips for Exam Success | 考试成功技巧
When you face a case study question in your OCR Year 7 Science test, start by reading the introduction slowly. Highlight the aim, the variables and any numbers with a pencil. Next, scan any tables and graphs, noting the headings and units. Before writing any answer, spend 30 seconds planning what the question is actually asking — is it a ‘describe’ question, an ‘explain’ question, or an ‘evaluate’ question? The command word tells you exactly what to do.
当你在OCR Year 7科学测试中面对案例研究问题时，首先要慢慢阅读引言。用铅笔标出目的、变量和所有数字。接下来，浏览所有表格和图表，注意标题和单位。在书写任何答案之前，花30秒时间计划一下问题实际在问什么——是一个“描述”题、“解释”题还是“评估
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