Case Study in Scientific Enquiry: Thermal Insulation | 科学探究案例分析：保温性能实战演练

📚 Case Study in Scientific Enquiry: Thermal Insulation | 科学探究案例分析：保温性能实战演练

Welcome to this Year 7 CAIE Science case study! We will follow a student investigation and practise the key skills of scientific enquiry: identifying variables, writing a hypothesis, analysing data, drawing a graph, forming conclusions and evaluating the method. The scenario focuses on thermal insulation, a topic that combines physics and experimental design. Work through each section carefully – the questions and tasks will help you build confidence for your own practical assessments.

欢迎来到这个Year 7 CAIE科学案例分析！我们将跟随一项学生探究，练习科学探究的关键技能：识别变量、写出假设、分析数据、绘制图表、得出结论和评价方法。情景围绕热保温展开，这是一个结合物理与实验设计的话题。请仔细完成每一部分——这些问题和任务将帮助你在自己的实践评估中建立信心。

1. The Scenario | 案例情景

Amira and Lucas want to find out which material is the best at keeping a cup of hot water warm. They have four materials to test: cotton wool, sheep’s wool, foam sheets and shredded newspaper. They wrap each material around an identical glass beaker containing 200 cm³ of hot water at 80 °C. They place a cardboard lid on top of each beaker to reduce heat loss from the surface. After 10 minutes, they measure the temperature of the water using a thermometer.

Amira和Lucas想弄清楚哪种材料最能保持一杯热水温暖。他们有四种材料可以测试：棉絮、羊绒毛、泡沫板和碎报纸。他们将每种材料包裹在一个相同的玻璃烧杯上，烧杯内装有200 cm³温度为80 °C的热水。他们在每个烧杯顶部盖一块硬纸板以减少表面散热。10分钟后，他们用温度计测量水的温度。

2. Identifying Variables | 识别变量

In any fair test, we must keep certain things the same (control variables), change only one thing (independent variable) and measure the outcome (dependent variable). Read the scenario again and identify these three types of variable.

在任何公平实验中，我们必须保持某些因素不变（控制变量），只改变一件事（自变量）并测量结果（因变量）。再次阅读情景，识别这三种变量。

The independent variable is the type of insulating material (cotton wool, sheep’s wool, foam, newspaper). This is what Amira and Lucas purposely change.
自变量是保温材料的类型（棉絮、羊绒毛、泡沫、报纸）。这是Amira和Lucas有意改变的因素。

The dependent variable is the temperature of the water after 10 minutes (or the temperature drop). This is what they measure and what depends on the insulating material.
因变量是10分钟后水的温度（或下降的温度）。这是他们测量的内容，取决于保温材料。

Control variables include: the volume of water (200 cm³), the starting temperature (80 °C), the size and type of beaker, the waiting time (10 minutes), the thickness of the material layer and the presence of a cardboard lid. Keeping these the same makes the test fair.
控制变量包括：水的体积（200 cm³）、起始温度（80 °C）、烧杯的大小和类型、等待时间（10分钟）、材料层的厚度以及使用硬纸板盖子。保持这些条件相同使测试公平。

3. Stating a Hypothesis | 提出假设

A hypothesis is a testable prediction. It often uses the format: ‘If …, then … because …’ Write a hypothesis for this investigation.

假设是一个可检验的预测。它通常采用这样的格式：“如果……，那么……，因为……”为这项探究写一个假设。

Example hypothesis: If foam is used as the insulator, then the water will have the highest temperature after 10 minutes (or the smallest temperature drop), because foam contains many trapped air pockets which are poor conductors of heat.

假设示例：如果使用泡沫作为保温材料，那么10分钟后水的温度会最高（或者说温度下降最小），因为泡沫含有许多被困住的空气囊，这些空气囊是热的不良导体。

You could also predict that shredded newspaper will be the least effective because it has larger air gaps where heat can escape more easily. Remember, your prediction must be based on scientific reasoning.

你也可以预测碎报纸效果最差，因为它有较大的空气间隙，热量更容易散失。记住，你的预测必须基于科学推理。

4. The Method | 实验方法

Here is a step-by-step list of the procedure Amira and Lucas followed. Put them in the correct order by numbering 1 to 7.

以下是Amira和Lucas所遵循的步骤列表。请按正确顺序将它们编号为1至7。

Pour 200 cm³ of hot water at exactly 80 °C into each of five identical beakers. | 将200 cm³恰好80 °C的热水倒入五个相同的烧杯中。
Wrap one beaker with a 2 cm thick layer of cotton wool, securing it with an elastic band. | 用一个2厘米厚的棉絮层包裹一个烧杯，用橡皮筋固定。
Repeat Step 2 for sheep’s wool, foam and shredded newspaper. Leave one beaker unwrapped as a control. | 对羊绒毛、泡沫和碎报纸重复步骤2。留下一个烧杯不包裹作为对照。
Place a cardboard lid on each beaker immediately after wrapping. | 包裹后立即在每个烧杯上盖一块硬纸板。
Start the stopwatch as soon as all beakers are ready. | 所有烧杯准备好后立即启动秒表。
After exactly 10 minutes, carefully measure the water temperature in each beaker with a thermometer. | 10分钟整后，用温度计仔细测量每个烧杯中的水温。
Record the results in a table. | 将结果记录在表格中。

5. Results and Data | 结果与数据

The table below shows the temperature readings Amira and Lucas collected. Study the data carefully.

下表显示了Amira和Lucas收集的温度读数。仔细研究数据。

Material / 材料	Starting temperature / 起始温度 (°C)	Temperature after 10 min / 10分钟后温度 (°C)	Temperature drop / 温度下降 (°C)
Cotton wool / 棉絮	80	62	18
Sheep’s wool / 羊绒毛	80	64	16
Foam / 泡沫	80	71	9
Shredded newspaper / 碎报纸	80	58	22
No insulation (control) / 无保温 (对照组)	80	45	35

Calculate the temperature drop for each material by subtracting the final temperature from the starting temperature. The control beaker lost the most heat (35 °C drop), while the foam-wrapped beaker lost the least (only 9 °C drop).

通过从起始温度中减去最终温度，计算每种材料的温度下降值。对照组烧杯热量散失最多（下降35 °C），而泡沫包裹的烧杯热量散失最少（仅下降9 °C）。

6. Drawing a Graph | 绘制图表

Now it is your turn to visualise the data. On a piece of graph paper or using a spreadsheet, draw a bar chart to show the temperature drop for each material. Label the x-axis ‘Type of insulation’ and the y-axis ‘Temperature drop (°C)’. Make sure you use an even scale on the y-axis (for example, 1 cm = 5 °C) and give your chart a clear title.

现在轮到你将数据可视化。在坐标纸或使用电子表格中，绘制一个条形图来展示每种材料的温度下降值。将x轴标记为“保温材料类型”，y轴标记为“温度下降 (°C)”。确保在y轴上使用均匀的比例（例如，1厘米 = 5 °C），并给图表一个清晰的标题。

A well-drawn bar chart should have the bars separated, consistent bar width, accurate plotting and both axes fully labelled. The foam bar will be the shortest, showing it kept the water warmest.

一幅绘制良好的条形图应具有分开的条形、一致的条形宽度、精确的绘制和完全标记的坐标轴。泡沫的条形将是最短的，表明它最能保持水温。

7. Analysing Data and Patterns | 分析数据与模式

Look at the completed graph and the table. Which material was the best insulator? Which was the worst? Can you see a pattern linking the structure of a material to its insulating ability?

观察完成的图表和表格。哪种材料是最好的绝缘体？哪种最差？你能看到材料的结构与其保温能力之间的联系吗？

Foam was the best insulator because it had the smallest temperature drop (9 °C). Shredded newspaper was the worst among the wrapped beakers (22 °C drop). The pattern suggests that materials which trap still air in small pockets are better insulators. Foam is full of tiny closed air cells, while newspaper has larger, less sealed gaps. The control beaker with no wrap lost heat fastest because there was no layer to slow down conduction and convection.

泡沫是最好的绝缘体，因为它的温度下降最小（9 °C）。在包裹的烧杯中，碎报纸效果最差（下降22 °C）。这种模式表明，能在小气穴中困住静止空气的材料是更好的绝缘体。泡沫充满了微小的封闭气室，而报纸则有更大、密封性较差的气隙。没有包裹的对照组烧杯热量散失最快，因为没有层来减缓传导和对流。

8. Drawing Conclusions | 得出结论

A good conclusion states whether the results support the hypothesis, summarises the findings and uses scientific knowledge to explain them. Write a conclusion for Amira and Lucas’s investigation.

一个好的结论会说明结果是否支持假设，总结研究发现，并运用科学知识加以解释。为Amira和Lucas的探究写一个结论。

Example: The results support the hypothesis that foam would be the best insulator. The water wrapped in foam cooled by only 9 °C compared to 35 °C for the control. Foam works well because it contains many trapped air pockets, and air is a poor thermal conductor. This reduces heat loss through conduction. The experiment also showed that all materials provided some insulation, as even the newspaper-wrapped beaker lost less heat than the unwrapped one. To be fully certain, the experiment should be repeated.

示例：结果支持了泡沫会是最佳绝缘体的假设。用泡沫包裹的水仅冷却了9 °C，而对照组为35 °C。泡沫之所以有效，是因为它含有许多被困住的空气囊，而空气是热的不良导体。这减少了因传导造成的热量损失。实验还表明，所有材料都提供了一定的保温效果，因为即使包裹报纸的烧杯也比未包裹的散热少。为了完全确认，实验应该重复进行。

9. Evaluating the Experiment | 评估实验

No experiment is perfect. Amira and Lucas must think about what went well and what could be improved. Here are some evaluation points to consider.

没有实验是完美的。Amira和Lucas必须考虑哪些地方做得好，哪些地方可以改进。以下是一些评估要点需要考虑。

What worked well: They used a control beaker to show the effect of no insulation. They covered the beakers with lids to reduce evaporation and convection. They measured the temperature at a fixed time.

做得好的方面：他们使用了对照烧杯来展示无保温的效果。他们用盖子盖住烧杯以减少蒸发和对流。他们在固定时间测量温度。

Limitations: Wrapping thickness might not have been exactly the same for all materials because the newspaper was shredded and harder to keep uniform. The room temperature may have changed during the experiment. Only one set of readings was taken, so there is no way to check reliability. The thermometer might have been read at slightly different depths or times if they were not very careful.

局限性：所有材料的包裹厚度可能不完全相同，因为报纸是碎状的，更难保持均匀。实验期间室温可能发生了变化。只采集了一组读数，因此无法检查可靠性。如果他们不够小心，温度计可能在不同深度或稍有不同的时刻读取。

10. Suggesting Improvements | 提出改进建议

Based on the evaluation, suggest three practical improvements to the investigation. Explain each one.

根据评估，为探究提出三项实际改进建议，并解释每项建议。

Repeat the experiment twice more and calculate an average temperature drop for each material. This makes the results more reliable and reduces the effect of random errors. | 将实验重复两次，并为每种材料计算平均温度下降值。这使得结果更可靠，并减少随机误差的影响。
Use materials of equal thickness by compressing them with a rigid sleeve or measuring with a ruler. This ensures a fairer test because thickness affects insulation. | 通过用硬质套管压实或用尺子测量，使用等厚度的材料。这确保测试更公平，因为厚度会影响保温效果。
Place all beakers in a water bath at a constant room temperature to minimise changes in surroundings, or measure room temperature regularly. | 将所有烧杯放置在恒定室温的水浴中，以尽量减少环境变化，或定期测量室温。

11. Real-World Applications | 实际应用

Insulation is used everywhere. Can you think of two examples where good thermal insulation is important in daily life? Explain how the trapped air principle works in each case.

保温材料到处都在使用。你能想到日常生活中两个需要良好保温的例子吗？解释每个例子中困住空气的原理是如何起作用的。

A thermos flask (vacuum flask) has a double wall with a vacuum between, but also a reflective surface; however, many cheaper flasks use foam insulation. The foam traps air and slows down heat transfer, keeping drinks hot or cold. | 保温瓶（真空瓶）有双层壁，中间是真空，还有反射表面；不过，许多较便宜的保温瓶使用泡沫保温。泡沫困住空气并减缓热传递，保持饮料热或冷。
House loft insulation is often made of fibreglass wool, which works like sheep’s wool or cotton wool. It traps air in narrow spaces, reducing heat loss through the roof, saving energy. | 房屋阁楼保温层常由玻璃纤维棉制成，其作用类似于羊绒毛或棉絮。它在狭窄空间内困住空气，减少通过屋顶的热量散失，节约能源。

12. Extension Questions | 延伸思考

Think deeper and answer these questions in full sentences.

深入思考，并用完整句子回答这些问题。

Explain why metals are not good insulators. | 解释为什么金属不是好的绝缘体。
If the students used boiled water at 100 °C instead of 80 °C, predict what would happen to the temperature drop after 10 minutes and justify your prediction. | 如果学生使用100 °C的开水而不是80 °C，预测10分钟后温度下降会发生什么变化，并证明你的预测。
Describe how you could adapt this experiment to test which colour of beaker is best at reducing heat loss by radiation. | 描述你如何调整这个实验，以测试哪种颜色的烧杯最能减少辐射热损失。

Suggested answers: Metals are good thermal conductors because they have free electrons that transfer energy quickly. At a higher starting temperature, the temperature drop would likely be larger because the rate of heat loss is greater when the temperature difference between the water and the room is bigger. To test colour and radiation, you could paint identical beakers with different colours (black, white, shiny silver) and leave them uncovered with the same starting temperature, measuring the drop over time.

参考答案：金属是热的良导体，因为它们有自由电子，能快速传递能量。在较高的起始温度下，温度下降幅度可能会更大，因为水与室内的温差越大，热量散失的速率就越快。要测试颜色和辐射，你可以将相同的烧杯涂上不同的颜色（黑色、白色、闪亮的银色），不加覆盖，以相同的起始温度，测量一段时间内的温度下降。

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Case Study in Scientific Enquiry: Thermal Insulation | 科学探究案例分析：保温性能实战演练