📚 Year 9 SQA Science: Case Study Practical Exercises | Year 9 SQA 科学：案例分析实战演练
Case studies in SQA Science allow you to apply scientific knowledge to real-world situations, honing your analytical and evaluation skills. This article guides you through practical exercises, using typical Year 9 scenarios, to help you master case study questions in your assessments.
SQA 科学中的案例分析让你将科学知识应用于实际情况，锻炼分析和评估技能。本文通过典型的九年级情境，引导你进行实战练习，助你掌握评估中的案例研究题目。
1. Understanding Case Studies in SQA Science | 理解 SQA 科学中的案例分析
A case study in science is an in-depth investigation of a specific situation or problem. It requires you to use your knowledge of biology, chemistry and physics to interpret data, identify patterns, make predictions and evaluate evidence. In SQA assessments, case studies often present experimental data, graphs or scenarios that you need to analyse critically.
科学中的案例分析是对特定情境或问题的深入探究。它要求你运用生物学、化学和物理学知识来解释数据、识别规律、作出预测并评价证据。在 SQA 评估中，案例分析常常给出实验数据、图表或场景，需要你进行批判性分析。
These tasks assess not only factual recall but also skills such as designing experiments, controlling variables and drawing conclusions. Practising case studies will help you think like a scientist.
这类任务不仅考查事实记忆，还考查实验设计、变量控制和得出结论等技能。练习案例分析能帮助你像科学家一样思考。
2. Steps for Effective Case Analysis | 有效案例分析的步骤
To tackle any case study, follow a structured approach. This will ensure you address all parts of the question and provide a logical, well-supported answer.
要应对任何案例研究，请遵循一套结构化方法。这将确保你回答问题的各个部分，并提供有逻辑、有依据的答案。
Step 1 – Identify the problem and variables. Decide what the investigation aims to find out. Pick out the independent variable (what is changed), the dependent variable (what is measured) and the controlled variables (what must stay the same).
步骤 1 – 确定问题和变量。 明确调查的目的。找出自变量（被改变的量）、因变量（被测量的量）和控制变量（必须保持不变的量）。
Step 2 – Examine the data. Look at tables, graphs or descriptions. Note any trends, anomalies or relationships. Use numbers from the tables to support your observations.
步骤 2 – 检查数据。 查看表格、图表或描述。注意任何趋势、异常值或关系。用表格中的数字来支持你的观察。
Step 3 – Apply scientific knowledge. Explain why the patterns occur. Use concepts such as limiting factors, chemical reactions, energy transfers or predator-prey relationships.
步骤 3 – 应用科学知识。 解释这些模式为何发生。使用限制因素、化学反应、能量转移或捕食者-猎物关系等概念。
Step 4 – Draw conclusions. State what the findings mean, and relate them back to the hypothesis. Mention whether the data supports it.
步骤 4 – 得出结论。 说明研究结果意味着什么，并将其与假设联系起来。说明数据是否支持假设。
Step 5 – Evaluate the method. Discuss limitations, sources of error and ways to improve the experiment. Consider reliability (repeats) and accuracy (equipment).
步骤 5 – 评价方法。 讨论局限性、误差来源以及改进实验的方法。考虑可靠性（重复实验）和准确性（设备）。
3. Case Study 1: Photosynthesis and Light Intensity | 案例一：光合作用与光照强度
A student investigated how light intensity affects the rate of photosynthesis in pondweed. The number of oxygen bubbles produced per minute was recorded at different light intensities. The data is shown below.
一名学生研究了光照强度如何影响水草的光合作用速率。在不同光照强度下，记录了每分钟产生的氧气气泡数量。数据如下所示。
| Light intensity / lx | Bubbles per minute |
|---|---|
| 0 | 0 |
| 500 | 8 |
| 1000 | 15 |
| 1500 | 21 |
| 2000 | 25 |
| 2500 | 26 |
The results show a positive correlation: as light intensity increases, the bubble count rises. This supports the idea that light is a limiting factor for photosynthesis. The rate of increase is rapid at first, but between 1500 lx and 2500 lx the curve begins to flatten.
结果显示正相关：随着光照强度增加，气泡计数上升。这支持了光是光合作用限制因素的观点。起初增长速率很快，但在 1500 lx 至 2500 lx 之间，曲线开始变平。
The plateau suggests another factor, such as carbon dioxide concentration or temperature, has become limiting. To improve the investigation, the student should place the lamp at several fixed distances and repeat the experiment three times to calculate mean values, reducing the effect of random errors.
曲线趋于平稳表明，另一个因素（如二氧化碳浓度或温度）已成为限制因素。为改进实验，学生应将灯放在几个固定距离处，并重复实验三次以计算平均值，从而减少随机误差的影响。
4. Case Study 2: Effect of Acid Rain on Marble | 案例二：酸雨对大理石的影响
Marble is mainly calcium carbonate, CaCO₃. A class tested the effect of simulated acid rain on marble chips. They placed identical marble chips in solutions of different pH and measured the percentage mass loss after 24 hours.
大理石主要成分是碳酸钙 CaCO₃。一个班级测试了模拟酸雨对大理石碎块的影响。他们将相同的大理石块放入不同 pH 的溶液中，并在 24 小时后测量质量损失百分比。
| pH of solution | Mass loss (%) |
|---|---|
| 6.5 | 0.5 |
| 5.0 | 2.0 |
| 4.0 | 8.5 |
| 3.0 | 18.0 |
The trend is clear: the lower the pH (more acidic), the greater the mass loss. This happens because acid reacts with calcium carbonate, producing soluble calcium salt, water and carbon dioxide. The ionic equation is:
趋势很清楚：pH 越低（酸性越强），质量损失越大。这是因为酸与碳酸钙反应，生成可溶性钙盐、水和二氧化碳。离子方程式为：
CaCO₃ + 2H⁺ → Ca²⁺ + H₂O + CO₂
The independent variable was the pH; the dependent variable was mass loss. Control variables included surface area of chips, volume of solution and temperature. To make the data more reliable, the class could repeat the experiment for each pH and use a more precise balance.
自变量是 pH 值；因变量是质量损失。控制变量包括大理块的表面积、溶液体积和温度。为使数据更可靠，班级可以对每个 pH 值重复实验，并使用更精密的天平。
This case study illustrates how chemical knowledge explains environmental damage and how careful experimentation reveals quantitative relationships.
本案例说明了化学知识如何解释环境破坏，以及精心设计的实验如何揭示定量关系。
5. Case Study 3: Comparing Renewable Energy Sources | 案例三：可再生能源对比
A community is deciding which renewable energy source to install: wind, solar or hydroelectric. Your role is to analyse the data and recommend the best option, considering both environmental and economic factors.
某社区正在决定安装哪种可再生能源：风能、太阳能还是水力发电。你的任务是分析数据，并考虑环境和经济效益，推荐最佳方案。
| Energy source | Average output (kW) | Set-up cost (£/kW) | CO₂ saved (t/year) | Drawback |
|---|---|---|---|---|
| Wind | 800 | 1200 | 460 | Noise, visual impact |
| Solar | 600 | 900 | 350 | Needs large area |
| Hydro | 950 | 2000 | 550 | Flooding of valley |
Hydroelectricity gives the highest output and the greatest CO₂ saving, but it has the highest set-up cost and can displace wildlife through flooding. Solar energy has the lowest cost per kW but requires large areas and depends on sunny conditions. Wind power offers a good balance but faces public resistance due to noise.
水力发电输出最高、二氧化碳节约最多，但其安装成本最高，而且洪水可能导致野生动物迁移。太阳能每千瓦成本最低，但需要大面积且依赖晴天。风能提供了较好的平衡，但因噪音面临公众反对。
A valid recommendation would be to choose wind turbines unless the area has strong river flow, in which case hydro might be more suitable. Any choice should be justified by the data, mentioning trade-offs.
一个合理的建议是选择风力发电机，除非该地区有强劲的河流，那样水电站可能更适合。任何选择都应有数据支持，并说明权衡之处。
6. Case Study 4: Investigating a Food Chain Disruption | 案例四：探究食物链中断
ologists recorded population sizes over five years after a disease reduced the wolf population. The estimated numbers are shown below.
一个简化的森林生态系统食物链为：植物 → 鹿 → 狼。生态学家记录了狼群因疾病减少后五年内的种群数量。估计数字如下所示。
| Year | Wolves | Deer | Plant cover (%) |
|---|---|---|---|
| 1 | 50 | 200 | 70 |
| 2 | 20 | 280 | 65 |
| 3 | 15 | 400 | 45 |
| 4 | 18 | 380 | 40 |
| 5 | 25 | 320 | 55 |
When wolves decreased, the deer population surged because predation pressure was lowered. The increased grazing led to a decline in plant cover. By year 4, the deer numbers began to fall as food became scarce, allowing plant cover to recover slightly. Wolf numbers eventually started to rise again as prey became plentiful.
当狼减少时，鹿的数量因捕食压力降低而猛增。啃食增加导致植物覆盖减少。到第四年，鹿的数量因食物匮乏开始下降，植物覆盖略有恢复。随着猎物丰富，狼的数量最终开始回升。
This case illustrates predator-prey dynamics and the interdependence of organisms. Removing a top predator can unbalance the whole community. An evaluation of the data might note that other factors, such as disease or weather, could also influence the numbers.
此案例说明了捕食者-猎物动态以及生物的相互依赖。移除顶级捕食者可能会打破整个群落的平衡。数据评价可能指出，其他因素（如疾病或天气）也可能影响数量。
7. Case Study 5: Forces and Motion – Car Safety Features | 案例五：力与运动——汽车安全特性
Road safety researchers tested how speed affects stopping distance. A car was driven at different initial speeds on a dry surface. The reaction distance (distance travelled while driver reacts) and braking distance (distance travelled after braking) were recorded.
道路安全研究人员测试了速度如何影响停车距离。一辆汽车在干燥路面上以不同初速度行驶。记录了反应距离（驾驶员反应时间内行驶的距离）和制动距离（刹车后行驶的距离）。
| Initial speed (m/s) | Reaction distance (m) | Braking distance (m) | Total stopping distance (m) |
|---|---|---|---|
| 10 | 7 | 6 | 13 |
| 20 | 14 | 24 | 38 |
| 30 | 21 | 54 | 75 |
The relationship between speed and braking distance is non-linear: when speed doubles from 10 m/s to 20 m/s, braking distance quadruples from 6 m to 24 m. This is because braking distance is proportional to the square of the speed. The formula for stopping distance is:
速度与制动距离的关系是非线性的：当速度从 10 米/秒加倍到 20 米/秒时，制动距离从 6 米增加到 24 米，翻了两番。这是因为制动距离与速度的平方成正比。停车距离的公式是：
stopping distance = reaction distance
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