Year 8 OCR Science: Case Study Practical Drill | Year 8 OCR 科学：案例分析实战演练

📚 Year 8 OCR Science: Case Study Practical Drill | Year 8 OCR 科学：案例分析实战演练

In Year 8 OCR Science, case studies help students apply scientific methods to real-world problems. This practical drill takes you through a complete investigation step by step. Using a common question—”How does temperature affect the rate at which salt dissolves in water?”—you will practise planning, carrying out an experiment, recording data and drawing conclusions. This mirrors how scientists work in the lab and prepares you for key assessments.

在 Year 8 OCR 科学中，案例分析帮助学生将科学方法应用于现实问题。这份实战演练将带你逐步完成一项完整的探究。通过一个常见问题——“温度如何影响盐在水中的溶解速率？”——你将练习规划、实施实验、记录数据和得出结论。这反映了科学家在实验室中的工作方式，并帮助你为关键评估做好准备。

1. Introducing the Case Study | 案例介绍

Imagine you are helping in the kitchen. You add table salt to a pot of cold water and notice it takes a long time to dissolve. Your friend suggests using hot water next time to speed up the process. Is that true? In this case study, you will investigate the relationship between temperature and the rate of dissolving salt. This is a classic example of a scientific inquiry where you can control variables, make measurements and analyse data to find an answer.

想象一下你在厨房帮忙。你将食盐加入一锅冷水中，并注意到它需要很长时间才能溶解。你的朋友建议下次用热水来加快这个过程。这是真的吗？在本案例中，你将探究温度与盐溶解速率之间的关系。这是一个科学探究的经典例子，你可以控制变量、进行测量和分析数据来找到答案。

2. Identifying the Scientific Question | 确定科学问题

Every good investigation starts with a clear, focused question. After a brief discussion, you phrase it as: “How does the temperature of water affect the time taken for a fixed mass of salt to dissolve completely?” This question is measurable and allows for a fair test. It also includes the key factors: temperature (independent variable) and dissolving time (dependent variable).

每一项好的探究都始于一个清晰、聚焦的问题。经过简短讨论后，你将问题表述为：“水的温度如何影响固定质量的盐完全溶解所需的时间？”这个问题是可测量的，并且可以进行公平测试。它还包含了关键因素：温度（自变量）和溶解时间（因变量）。

3. Formulating a Hypothesis | 形成假设

Based on your everyday observations, you propose a hypothesis: “Increasing the temperature of the water will decrease the time taken for the salt to dissolve.” This is a prediction that can be tested. You might reason that warmer water particles have more kinetic energy, so they collide with the salt crystals more frequently and with greater force, breaking them apart faster.

基于你的日常观察，你提出一个假设：“提高水的温度会减少盐溶解所需的时间。” 这是一个可以被检验的预测。你可能会推断，较热的水颗粒具有更高的动能，因此它们会更频繁且更有力地与盐晶体碰撞，从而更快地将其分解。

4. Variables in the Investigation | 调查中的变量

To carry out a fair test, you must identify and control variables. The independent variable is the one you change deliberately: the temperature of the water. The dependent variable is what you measure: the time taken for the salt to dissolve completely. All other factors must be kept constant as control variables.

为了进行公平测试，你必须确定并控制变量。自变量是你有意改变的：水的温度。因变量是你测量的：盐完全溶解所需的时间。所有其他因素必须作为控制变量保持不变。

Key control variables include the mass of salt used (5.0 g), the volume of water (100 cm³), the type of salt (pure sodium chloride), the shape of the container and no stirring. All experiments are carried out at the same atmospheric pressure. By keeping these constant, you ensure that any change in dissolving time is due only to temperature.

关键控制变量包括使用的盐的质量（5.0克）、水的体积（100立方厘米）、盐的种类（纯氯化钠）、容器的形状以及不搅拌。所有实验均在相同大气压下进行。通过保持这些变量不变，你确保溶解时间的任何变化仅由温度引起。

5. Designing the Experiment | 设计实验

You need a simple procedure that is easy to repeat. The equipment list is shown in the table below.

你需要一个简单且易于重复的操作步骤。设备清单如下表所示。

Procedure: 1) Use the balance to weigh exactly 5.0 g of salt. 2) Measure 100 cm³ of water using the measuring cylinder and pour it into the beaker. 3) Adjust the water to the desired temperature using a water bath or adding hot/cold water and check with the thermometer. Target temperatures: 10 °C, 20 °C, 30 °C, 40 °C, 50 °C. 4) Add the salt to the water and start the stopwatch immediately. Do not stir. 5) Observe carefully and stop the timer the moment no solid salt is visible. Record the time. 6) Repeat each temperature trial three times for reliability and calculate the mean time.

步骤：1) 使用天平准确称量5.0克盐。2) 用量筒量取100立方厘米水，倒入烧杯中。3) 使用水浴或加入热水/冷水调节水温至所需温度，并用温度计检查。目标温度：10 °C、20 °C、30 °C、40 °C、50 °C。4) 将盐加入水中并立即启动秒表。不要搅拌。5) 仔细观察，在看不见固体盐的瞬间停止计时。记录时间。6) 每个温度重复实验三次以确保可靠性，并计算平均时间。

6. Recording Data | 记录数据

You design a results table to collect raw data. A well-structured table makes it easier to spot patterns.

你设计一个结果表格来收集原始数据。结构良好的表格更容易发现规律。

Example data recorded during the investigation:

调查中记录的示例数据：