Case Study Practical Exercises | 案例分析实战演练

📚 Case Study Practical Exercises | 案例分析实战演练

In CAIE Year 9 Science, case study questions test your ability to apply scientific concepts to unfamiliar situations. You need to analyse data, identify variables, evaluate experimental methods and draw evidence-based conclusions. By practising structured case studies, you build the skills required for high marks.

在CAIE九年级科学中，案例分析题考查你是否能将科学概念应用到陌生情境中。你需要分析数据、识别变量、评估实验方法并得出基于证据的结论。通过结构化的案例练习，你能培养获得高分所需的技能。

1. Importance of Case Studies in CAIE Science | 案例分析在CAIE科学中的重要性

Case studies are a key component of the CAIE Science examination. They present a scenario, often with a data table or diagram, followed by questions that require you to think like a scientist. Performing well means not just recalling facts, but interpreting evidence, spotting errors, and suggesting improvements.

案例分析是CAIE科学考试的关键组成部分。它们给出一个情境，常配有数据表或示意图，随后的问题需要你像科学家一样思考。表现出色不仅意味着回忆事实，更要会解读证据、发现错误并提出改进。

2. Overview of a Case Study Approach | 案例分析步骤概览

A successful case study answer follows a logical sequence: (1) Read the scenario carefully and underline key scientific terms. (2) Identify the independent, dependent and control variables. (3) Describe the trend or pattern in the data. (4) Use scientific knowledge to explain the results. (5) Evaluate the method, noting limitations and suggesting refinements.

一个成功的案例分析答案遵循逻辑顺序：(1) 仔细阅读情境，划出关键科学术语。(2) 找出自变量、因变量和控制变量。(3) 描述数据中的趋势或模式。(4) 用科学知识解释结果。(5) 评价实验方法，指出局限性并提出改进。

3. Case 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. She placed a lamp at different distances from a beaker containing pondweed and recorded the number of oxygen bubbles produced per minute.

一位学生探究了光照强度对水草光合作用速率的影响。她在距离烧杯不同位置放置一盏灯，烧杯中有水草，记录每分钟产生的氧气气泡数。

Distance (cm): 10, 20, 30, 40, 50. Bubbles per minute: 45, 32, 20, 10, 5.

距离（厘米）：10、20、30、40、50。每分钟气泡数：45、32、20、10、5。

Variable identification: Independent variable: distance of the lamp (light intensity). Dependent variable: number of bubbles per minute (rate of photosynthesis). Controlled variables: temperature, carbon dioxide concentration (added sodium hydrogen carbonate solution), type of pondweed, time allowed for each measurement.

变量识别： 自变量：灯的距离（光照强度）。因变量：每分钟气泡数（光合作用速率）。控制变量：温度、二氧化碳浓度（添加碳酸氢钠溶液）、水草种类、每次测量允许的时间。

Trend analysis: As the distance increases, the number of bubbles decreases. This is because light intensity decreases with distance (inverse square law), so less energy is available for photosynthesis.

趋势分析： 随着距离增加，气泡数减少。这是因为光照强度随距离增加而减弱（平方反比定律），可用于光合作用的能量减少。

Evaluation and improvements: Bubbles may vary in size, causing inaccuracy. The lamp may heat the water, changing temperature. Improvements: use a water bath to control temperature, measure gas volume using a gas syringe instead of counting bubbles, and repeat readings.

评估与改进： 气泡大小可能不一，导致不准确。灯可能加热水，改变温度。改进方法：使用水浴控制温度，用气体注射器测量气体体积而不是计数气泡，并重复读数。

4. Case 2: Temperature and Reaction Rate | 案例二：温度对反应速率的影响

A student mixed magnesium ribbon with dilute hydrochloric acid and measured the time taken to collect 10 cm³ of hydrogen gas at different temperatures. The data are shown below.

一位学生将镁条与稀盐酸混合，测量在不同温度下收集10 cm³氢气所需的时间。数据见下表。

Temperature (°C): 20, 30, 40, 50, 60. Time (s): 50, 32, 18, 10, 6.

温度（°C）：20，30，40，50，60。时间（秒）：50，32，18，10，6。

Variables: Independent: temperature; dependent: time taken (reaction rate); controls: volume and concentration of acid, length and mass of magnesium ribbon.

变量： 自变量：温度；因变量：所用时间（反应速率）；控制变量：酸的体积与浓度、镁条的长度和质量。

Pattern: As temperature rises, the reaction time decreases, so the reaction rate increases. This occurs because particles move faster and collide more frequently and with greater energy, exceeding the activation energy.

模式： 温度升高时，反应时间缩短，因此反应速率增大。这是因为粒子运动加快，碰撞更频繁且能量更高，超过活化能。

Evaluation: The temperature may not be constant throughout the reaction. Gas collection may start before timing begins. Improvements: use a water bath for precise temperature control, start timing immediately upon mixing, and use a gas syringe for accurate volume measurement.

评估： 反应过程中温度可能不恒定。气体收集可能在计时开始前已进行。改进：使用水浴精确控温，混合后立即开始计时，用气体注射器准确测量体积。

5. Case 3: Friction on Different Surfaces | 案例三：不同表面的摩擦力

An investigation measured the force needed to pull a wooden block at constant speed across three surfaces: a smooth wooden board, sandpaper and carpet. A spring balance was used to record the force.

一项调查测量了在三种表面上以恒定速度拉动木块所需的力：光滑木板、砂纸和地毯。使用弹簧秤记录力。

Published by TutorHao | Year 9 Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）