📚 Year 8 WJEC Science: Case Study Practice | Year 8 WJEC 科学：案例分析实战演练
In WJEC Year 8 Science, case studies allow you to explore real‑world situations through the lens of scientific principles. Rather than simply recalling facts, you will analyse evidence, apply your knowledge of biology, chemistry and physics, and evaluate conclusions. This article provides guided practice with seven detailed case studies and essential exam skills, helping you build confidence for your assessments.
在 WJEC 八年级科学课程中，案例分析让你通过科学原理的透镜探索真实世界的情境。你不仅要回忆事实，还要分析证据、运用生物、化学和物理知识并评估结论。本文通过七个详细的案例研究和必备的考试技能训练，帮助你建立自信，应对测评。
1. What Is a Case Study in Science? | 科学中的案例分析是什么？
A case study is an in‑depth investigation of a specific event, process or problem, using scientific methods and knowledge to explain observations and make decisions. In your WJEC papers, case studies often present data (tables, graphs, descriptions) that you must interpret to answer questions about causes, effects and solutions.
案例分析是对特定事件、过程或问题的深入探究，运用科学方法和知识解释观察结果并做出决策。在 WJEC 试卷中，案例研究通常会给出数据（表格、图表、描述），你需要解读它们来回答关于原因、影响和解决方案的问题。
For example, a case study might describe a sudden drop in a bird population and ask you to identify the environmental factor responsible, using your understanding of food chains and pollution. You are expected to link the evidence to scientific theories, not just state an opinion.
例如，一个案例研究可能描述某种鸟类数量突然下降，要求你运用食物链和污染的知识，找出导致变化的环境因素。你需要将证据与科学理论联系起来，而不仅仅是陈述观点。
2. How to Approach a WJEC Case Study Question | 如何解答 WJEC 案例分析题
Follow this step‑by‑step method to tackle any case study with confidence. Practise these stages now so they become automatic during the exam.
遵循以下逐步方法，自信地应对任何案例分析。现在练习这些步骤，让它们在考试中成为习惯。
Read the scenario carefully, highlighting key scientific terms and units. | 仔细阅读情境，标出关键科学术语和单位。
Identify the relevant scientific concepts – is it about forces, chemical reactions, ecosystems or human biology? | 确定相关的科学概念——是关于力、化学反应、生态系统还是人体生物学？
Extract data from tables, graphs or text; note any patterns or anomalies. | 从表格、图表或文字中提取数据；注意任何规律或异常。
Perform calculations where needed, using correct units (e.g. m/s², kJ, g/cm³). | 在需要时进行计算，使用正确单位（如 m/s²、kJ、g/cm³）。
Analyse the evidence – why did something happen? What are the consequences? | 分析证据——某事为什么会发生？后果是什么？
Evaluate the reliability of the information and suggest improvements to the investigation. | 评估信息的可靠性，并对调查提出改进建议。
Communicate your findings clearly, using appropriate scientific vocabulary. | 使用恰当的科学词汇清晰地交流你的发现。
3. Case Study 1: Investigating Water Pollution | 案例一：调查水污染
A local stream that once supported trout and mayflies has seen fish dying and a green slime covering the surface. Scientists tested water samples and found high nitrate (45 mg/L) and phosphate (8 mg/L) levels, far above the natural background. The stream runs near farmland where fertilisers are used intensively.
一条曾养育鳟鱼和蜉蝣的当地溪流，出现了鱼类死亡和水面覆盖绿色黏泥的现象。科学家检测水样，发现硝酸盐（45 mg/L）和磷酸盐（8 mg/L）浓度远高于自然背景值。溪流附近是大量使用化肥的农田。
The high nutrient levels cause eutrophication. Fertilisers rich in nitrates and phosphates are washed into the water, promoting excessive growth of algae. These algae form dense blooms that block sunlight, killing aquatic plants. When the algae die, bacteria decompose them, consuming dissolved oxygen. Oxygen levels plummet, suffocating fish and invertebrates.
高营养物浓度导致了富营养化。富含硝酸盐和磷酸盐的肥料被冲入水中，促使藻类过度生长。这些藻类形成密集的水华，遮挡阳光，杀死水生植物。藻类死亡后，细菌分解它们，消耗溶解氧。氧含量急剧下降，使鱼类和无脊椎动物窒息。
en dropped from 8 mg/L to 2 mg/L downstream. You can calculate the percentage decrease: (8 – 2) / 8 × 100% = 75% . To solve the problem, farmers could use buffer strips and reduce fertiliser application.
数据记录仪显示下游溶解氧从 8 mg/L 降至 2 mg/L。可以计算下降百分比：(8 – 2) / 8 × 100% = 75%。这解释了为什么敏感物种消失了。解决问题的方法是农民可以采用缓冲带并减少施肥量。
4. Case Study 2: Energy Efficiency in the Home | 案例二：家庭能源效率
Home energy bills can be reduced by improving insulation. A homeowner compared heat loss through a wall made of brick, brick with glass‑fibre insulation, and brick with foam insulation. The U‑value (rate of heat transfer) was measured in W/m²K under the same temperature difference of 20°C.
改善隔热可以降低家庭能源费用。一位房主比较了仅砖墙、砖墙加玻璃纤维保温层以及砖墙加泡沫保温层墙壁的热量损失。在相同温差 20°C 条件下测量了 U 值（传热速率），单位为 W/m²K。
| Insulation Type | 保温类型 | U‑value (W/m²K) | Annual Energy Cost | 年能源费用 (£) |
|---|---|---|
| Brick only | 仅砖墙 | 1.6 | 640 |
| Glass‑fibre | 玻璃纤维 | 0.5 | 200 |
| Foam | 泡沫 | 0.3 | 120 |
The data show that adding insulation significantly lowers the U‑ trapped air in the material reduces conduction. Foam insulation gives the greatest saving: £640 – £120 = £520 per year. Payback period can be calculated if installation cost is known – for example, if foam costs £ ck = 2600/520 = 5 years. This is a strong scientific argument for investing in insulation.
数据表明，增加保温层显著降低了 U 值，因为材料中滞留的空气减少了热传导。泡沫保温节省最多：640 英镑 – 120 英镑 = 520 英镑/年。若已知安装成本，可计算回收期——例如，若泡沫保温费用为 2600 英镑，回收期 = 2600/520 = 5 年。这是投资保溫的有力科学依据。
5. Case Study 3: The Human Digestive System at Work | 案例三：人体消化系统的工作
A 12‑year‑old student often feels bloated and has stomach cramps after drinking milk or eating ice cream. A doctor suspects lactose intolerance. Lactose is a disaccharide sugar found in milk, normally broken down by the enzyme lactase into glucose and galactose. If lactase is deficient, lactose remains undigested, drawing water into the intestine and fermenting, causing gas and discomfort.
一名 12 岁学生喝牛奶或吃冰淇淋后经常感到腹胀和胃痉挛。医生怀疑是乳糖不耐受。乳糖是牛奶中的一种二糖，通常被乳糖酶分解为葡萄糖和半乳糖。如果乳糖酶缺乏，乳糖就无法消化，把水分吸入肠道并发酵，引起气体和不适。
A hydrogen breath test was performed: after consuming 25 g of lactose, breath hydrogen rose from 5 ppm to 65 ppm in 90 minutes. High hydrogen indicates bacterial fermentation of undigested lactose. The enzyme activity can be modelled with the lock‑and‑key hypothesis – lactase’s active site specifically fits the lactose molecule. Without the enzyme, the reaction rate is negligible.
进行了氢气呼气测试：摄入 25 克乳糖后，90 分钟内呼气氢气从 5 ppm 升至 65 ppm。高氢气表明未消化的乳糖被细菌发酵。酶活性可用锁钥假说建模——乳糖酶的活性部位与乳糖分子特异性契合。没有酶，反应速率微乎其微。
The solution is to avoid lactose‑rich foods or take lactase supplements. This case illustrates how a biological malfunction can be explained by enzyme specificity and provides evidence for dietary management.
解决方案是避免富含乳糖的食物或摄入乳糖酶补充剂。这个案例说明，可以用酶的专一性解释生物功能失调，并为饮食管理提供证据。
6. Case Study 4: Chemical Reactions in Cooking | 案例四：烹饪中的化学反应
When baking a cake, the batter rises thanks to chemical reactions. Sodium hydrogencarbonate (baking soda) decomposes upon heating, producing carbon dioxide gas. This gas becomes trapped in the batter, forming bubbles that expand and make the cake light and fluffy. The reaction is:
烤蛋糕时，面糊因化学反应而膨胀。碳酸氢钠（小苏打）加热分解，产生二氧化碳气体。气体被困在面糊中，形成气泡，膨胀后使蛋糕松软蓬松。反应为：
2 NaHCO₃ → Na₂CO₃ + CO₂ + H₂O
If an acidic ingredient like lemon juice is added, a separate acid‑base reaction occurs more rapidly, releasing CO₂ even at room temperature. The chemical test for carbon dioxide – bubbling through limewater turns it milky – confirms the gas produced.
如果加入柠檬汁等酸性食材，会更快发生酸碱反应，甚至在室温下释放 CO₂。二氧化碳的化学检验——通入石灰水变浑浊——可确认生成的气体。
Another reaction, caramelisation, happens when sugar is heated above 160°C. Sucrose molecules break down into hundreds of flavour compounds, giving a golden‑brown colour and sweet aroma. Understanding these reactions helps control the quality of baked goods and demonstrates the practical importance of chemistry.
另一种反应——焦糖化，在糖加热到 160°C 以上时发生。蔗糖分子分解成数百种风味化合物，呈现金褐色和甜美香气。了解这些反应有助于控制烘焙食品的品质，并展示化学的实践重要性。
7. Case Study 5: Forces and Motion in Sports | 案例五：体育运动中的力与运动
During a penalty kick, a football player strikes a stationary ball of mass 0.45 kg with an average force of 90 N. The contact time between foot and ball is 0.05 seconds. You can calculate the acceleration and final speed using Newton’s second law and kinematic equations.
在罚点球时，球员以 90 N 的平均力踢一个静止的 0.45 kg 足球。脚与球的接触时间为 0.05 秒。你可以用牛顿第二定律和运动学方程计算加速度和最终速度。
acceleration a = F / m = 90 N / 0.45 kg = 200 m/s²
.05 = 10 m/s (about 36 km/h). After leaving the foot, the ball experiences opposing forces – air resistance and friction with the ground – gloves increase friction, helping to catch the ball by providing a larger stopping force.
利用公式 v = u + at，其中 u = 0 m/s、t = 0.05 s，最终速度 v = 0 + 200 × 0.05 = 10 m/s（约 36 km/h）。球离开脚后会受到空气阻力和地面摩擦力等对抗力，使其减速。守门员手套增大摩擦力，提供更大的停止力来抓住球。
This case shows how sports performance can be analysed with simple physics. By adjusting force and angle, the kick can be optimised for distance and accuracy.
这个案例展示了如何用简单的物理知识分析运动表现。通过调整力和角度，可以优化踢球的距离和准确性。
8. Case Study 6: Ecosystems and Conservation | 案例六：生态系统与保护
A woodland ecosystem consists of oak trees (producers), caterpillars (primary consumers), blue tits (secondary consumers) and sparrowhawks (tertiary consumers). Over a five‑year period, the caterpillar population declined by 40%, and blue tit numbers also fell. Investigation revealed that heavy pesticide use on nearby fields had drifted into the woodland, killing caterpillars directly.
一个林地生态系统由橡树（生产者）、毛虫（初级消费者）、蓝山雀（次级消费者）和雀鹰（三级消费者）组成。五年间，毛虫数量下降了 40%，蓝山雀数量也随之减少。调查发现，附近田地大量使用的杀虫剂飘到了林地，直接杀死了毛虫。
A pyramid of numbers shows that the caterpillar population is normally much larger than the bird populations. With fewer caterpillars, the blue tits lack sufficient food, reducing their breeding success. The sparrowhawks then experience a secondary decline. Biologists recommended creating hedgerow buffers and using biological pest control to restore the food chain.
数量金字塔显示毛虫种群通常远大于鸟类种群。毛虫减少导致蓝山雀食物不足，繁殖成功率下降。雀鹰随后也出现次级衰退。生物学家建议建立灌木缓冲带并采用生物防治，以恢复食物链。
This case highlights interdependence in an ecosystem. Removing one level affects all others, demonstrating the importance of biodiversity and careful pesticide management.
这个案例突出了生态系统的相互依存关系。移除一个营养级会影响所有其他营养级，展示了生物多样性和谨慎管理农药的重要性。
9. Case Study 7: Medical Uses of Radiation | 案例七：辐射的医疗用途
Ionising radiation is used in medicine for both diagnosis and treatment. X‑rays pass through soft tissue but are absorbed by bones, creating images to detect fractures. A CT scan combines multiple X‑ray images to build a 3D picture of internal organs, but delivers a higher radiation dose than a simple X‑ray.
电离辐射在医学上用于诊断和治疗。X 射线能穿透软组织但被骨骼吸收，生成图像以检测骨折。CT 扫描结合多幅 X 射线图像构建内脏三维图像，但其辐射剂量高于普通 X 光片。
In cancer treatment, radiotherapy uses gamma rays (produced by radioactive isotopes such as cobalt‑60) to target and destroy malignant cells. The gamma rays are carefully aimed from multiple angles to minimise damage to healthy tissue. Alpha particles are not used externally because they cannot penetrate skin, but they can be injected in targeted alpha therapy for certain cancers.
在癌症治疗中，放射疗法使用伽马射线（由钴‑60 等放射性同位素产生）瞄准并摧毁恶性细胞。伽马射线从多个角度精确照射，减少对健康组织的伤害。α 粒子不用于外部治疗，因为它们无法穿透皮肤，但可通过靶向 α 疗法注射用于某些癌症。
The benefits of radiation must be weighed against the risks of causing DNA damage and secondary cancers. A case study of a thyroid cancer patient might involve iodine‑131, which the thyroid absorbs, delivering a localised dose while sparing the rest of the body. Understanding half‑life (8 days for iodine‑131) is crucial for planning safe treatment.
辐射的益处必须与引起 DNA 损伤和继发性癌症的风险相权衡。一个甲状腺癌患者的案例研究可能涉及碘‑131，它被甲状腺吸收，局部施药而保护身体其余部分。了解半衰期（碘‑131 为 8 天）对规划安全治疗至关重要。
10. Tips for Success in Case Study Exams | 案例研究考试的成功秘诀
Mastering case study questions requires practice and a structured approach. Always link your answers to scientific principles – do not just describe the data, explain it. Use the data to support your conclusions, quoting figures where appropriate.
掌握案例分析题需要练习和结构化方法。始终将答案与科学原理联系起来——不要只描述数据，要解释它。使用数据支持你的结论，适当引用数字。
Time management is key. Spend about 5 minutes reading and annotating the case study before writing. If a question asks you to evaluate, you must give both advantages and disadvantages or strengths and limitations of the investigation. Suggest realistic improvements, such as increasing sample size, using more precise instruments, or controlling more variables.
时间管理很关键。在动笔前花约 5 分钟阅读并批注案例。如果题目要求评估，你必须给出调查的优点和缺点，或优势和局限。提出切实可行的改进建议，例如增加样本量、使用更精密的仪器或控制更多变量。
Finally, revise the key concepts across biology, chemistry and physics so you can quickly spot which area of science applies. Practise with past paper case studies and ask your teacher for feedback on your responses. Over time, you will develop the analytical skills to excel.
最后，复习生物、化学和物理中的关键概念，以便迅速找出适用的科学领域。用真题案例进行练习，并请老师对你的答案提供反馈。随着时间的推移，你将培养出卓越的分析技能。
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