📚 Year 8 Edexcel Science: Case Study Practical Drill | Year 8 Edexcel 科学：案例分析实战演练
This article guides you through a complete case study investigation, modelling the type of scientific enquiry expected in Year 8 Edexcel Science. You will step into the role of a laboratory scientist tasked with testing antacid tablets. By following the logical sequence from planning to evaluation, you will strengthen your skills in handling variables, collecting data, identifying anomalies, drawing graphs and writing evidence‑based conclusions. The case study is built around a real application of neutralisation and fair testing, giving you a concrete example of how science is used to solve everyday problems.
本文将带你完成一个完整的案例分析探究，模拟 Year 8 Edexcel 科学课程所要求的科学探究方式。你将扮演一名实验室科学家，受命测试抗酸药片。通过按照从计划到评估的逻辑顺序进行学习，你将加强处理变量、收集数据、识别异常值、绘制图表以及撰写基于证据的结论等技能。本案例围绕中和反应与公平测试的实际应用展开，为你提供科学如何解决日常问题的具体示例。
1. Case Study Brief | 案例简介
You are a scientist working in the quality control department of a pharmaceutical company. Three brands of antacid tablets – labelled A, B and C – have arrived for testing. Your manager has asked you to determine which brand is the most effective at neutralising stomach acid. Stomach acid is mainly hydrochloric acid (HCl). You will simulate stomach conditions in the laboratory by using dilute hydrochloric acid of a known concentration. The investigation will be carried out by adding powdered antacid to a fixed volume of acid until neutralisation is complete, recording the mass of tablet used each time.
你是一名在某制药公司质量控制部门工作的科学家。三种品牌标为 A、B 和 C 的抗酸药片已送来接受测试。你的经理要求你确定哪种品牌在中和胃酸方面最有效。胃酸的主要成分是盐酸 (HCl)。你将在实验室中用已知浓度的稀盐酸来模拟胃内环境。本次探究将把药片粉末加入固定体积的酸中，直到中和完全，每次记录所用片剂的质量。
To make a fair comparison, you must keep all other factors constant. The mass of antacid needed to neutralise the acid is your indicator of effectiveness – the smaller the mass required, the more effective the antacid. You will need to produce a full scientific report, including a data table, a graph, an explanation of any anomalies and a final conclusion.
为了进行公平的比较，你必须使所有其他因素保持不变。中和酸液所需抗酸剂的质量即为效果的衡量指标 – 所需的质量越小，该抗酸剂的效果越好。你需要完成一份完整的科学报告，包括数据表、图表、对任何异常值的解释以及最终结论。
2. Chemical Background | 化学背景
d in a neutralisation reaction. The word equation for the reaction is: calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide. The balanced symbol equation is shown below:
许多抗酸药片含有碳酸钙 (CaCO₃) 作为有效成分。在胃中，碳酸钙与盐酸发生中和反应。该反应的文字表达式为：碳酸钙 + 盐酸 → 氯化钙 + 水 + 二氧化碳。配平后的符号方程式如下：
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)
The fizzing you observe is the production of carbon dioxide gas. The reaction continues until all the acid has been neutralised. At that point the pH of the solution rises to about 7 (neutral). In this investigation, you will use an indicator or a pH probe to judge when the neutralisation point is reached. Understanding this chemical principle helps you appreciate why different masses of antacid may be needed for different brands – they may contain different amounts of the active ingredient or other substances.
你所观察到的嘶嘶冒泡就是二氧化碳气体产生的现象。反应一直持续到所有酸被中和为止。此时，溶液的 pH 值上升至约 7（中性）。在本次探究中，你将使用指示剂或 pH 探头来判断中和点何时到达。理解这一化学原理有助于你理解为什么不同品牌的抗酸剂可能需要不同的质量 – 它们可能含有不同量的有效成分或其他物质。
3. Designing the Experiment | 实验设计
Before starting, you need a clear plan. The aim of the investigation is: 'To compare the effectiveness of three brands of antacid tablets by measuring the minimum mass needed to neutralise a fixed volume of dilute hydrochloric acid.' The independent variable is the brand of antacid (A, B or C). The dependent variable is the mass of antacid powder required to reach neutralisation. Controlled variables include the volume and concentration of hydrochloric acid, the temperature of the acid, the method of stirring and the particle size of the crushed tablets.
开始前，你需要一份清晰的计划。本次探究的目的是："通过测量中和固定体积稀盐酸所需的最小质量，比较三种品牌抗酸药片的效果。" 自变量是抗酸剂的品牌 (A、B 或 C)。因变量是达到中和所需的抗酸剂粉末的质量。控制变量包括盐酸的体积和浓度、酸的温度、搅拌方式以及压碎药片的颗粒大小。
Controlling the particle size is especially important. If tablets are crushed to different degrees, the rate of reaction will change because surface area affects how quickly the acid and antacid come into contact. You will use a mortar and pestle to grind each tablet to a fine powder and then sieve it to ensure a consistent grain size. This improves the reliability of the data.
控制颗粒大小尤其重要。如果药片被压碎的程度不同，反应速率就会改变，因为表面积会影响酸与抗酸剂接触的快慢。你将使用研钵和研杵把每片药片研磨成细粉，然后过筛以确保颗粒大小一致。这会提高数据的可靠性。
4. Identifying Variables | 识别变量
The following table summarises the key variables you must control, keep the same, or measure during the investigation. Being able to identify these variables is a core working scientifically skill for Year 8.
下表总结了你必须改变、保持不变或测量的关键变量。能够识别这些变量是 Year 8 阶段一项核心的科学工作技能。
| Variable Type | Variable | How it is managed |
|---|---|---|
| Independent (change) | Brand of antacid | Use tablets A, B and C |
| Dependent (measure) | Mass of antacid powder needed | Measure with digital balance to 0.01 g |
| Control (keep same) | Volume of acid | 25 cm³ each trial |
| Control | Concentration of acid | 0.1 mol/dm³ HCl |
| Control | Temperature | All trials at room temperature |
| Control | Particle size | Grind and sieve to same mesh size |
| Control | Stirring method | Magnetic stirrer at same speed |
By strictly controlling these variables, you can be confident that any difference in the mass needed is due to the brand of antacid and not to another factor. This is the essence of a fair test.
通过严格地控制这些变量，你便可以确信所需质量的任何差异都是由抗酸剂的品牌引起的，而非其他因素。这就是公平测试的核心。
5. Safety Precautions | 安全注意事项
Even with dilute acid, safety must be your first priority. Hydrochloric acid is an irritant. You must wear splash‑proof goggles and a lab coat at all times. Tie back long hair and tuck in loose clothing. If any acid spills on your skin, wash the area immediately with plenty of water. The experiment also involves glassware, so handle conical flasks and measuring cylinders carefully to avoid breakage. Crushing tablets produces fine dust; wearing a dust mask can prevent inhalation.
即便是稀酸，安全也必须是第一要务。盐酸具有刺激性。你必须始终佩戴防溅护目镜和实验服。把长发束起，并将宽松的衣物塞好。如果酸液溅到皮肤上，立即用大量清水冲洗。实验还涉及玻璃器皿，因此要小心拿取锥形瓶和量筒，以免破碎。压碎药片会产生细粉；佩戴口罩可以防止吸入。
Carry out the investigation in a well‑ventilated laboratory because carbon dioxide gas is produced, although the amounts are small. Always stand up while handling chemicals and never taste any substance. After the experiment, dispose of the neutralised solutions as directed by your teacher and wash your hands thoroughly. A risk assessment shows that with these controls, the activity is low risk.
因为会产生二氧化碳气体（尽管量很少），请在通风良好的实验室中进行探究。处理化学品时始终站立，切勿品尝任何物质。实验结束后，按照老师的指导处置中和后的溶液，并彻底清洗双手。风险评估显示，实施这些控制措施后，该活动风险较低。
6. Step-by-Step Method | 分步方法
The following method was written to obtain reliable results. Each step is numbered and uses precise language so that another scientist could repeat the experiment exactly.
以下方法是为获得可靠结果而编写的。每一步均有编号并使用了精确的语言，以便其他科学家能够准确地重复该实验。
Step 1: Measure 25.0 cm³ of 0.1 mol/dm³ hydrochloric acid using a measuring cylinder. Pour the acid into a clean 100 cm³ conical flask and place the flask on a magnetic stirrer. Add 3 drops of universal indicator solution; the acid turns red, confirming its acidic nature.
步骤 1：用量筒量取 25.0 cm³ 0.1 mol/dm³ 的盐酸。将酸倒入干净的 100 cm³ 锥形瓶中，并将锥形瓶放在磁力搅拌器上。滴加 3 滴通用指示剂溶液；酸变成红色，确认其酸性。
Step 2: Take one whole tablet of brand A and grind it into a fine powder using a mortar and pestle. Pass the powder through a sieve to remove any large lumps. Weigh an empty weighing boat and record its mass. Then use a spatula to transfer a small quantity of the powder into the weighing boat and place it on the digital balance (reading to 0.01 g). Record the mass of powder you are about to add.
步骤 2：取一整片品牌 A 的药片，用研钵和研杵研磨成细粉。将粉末过筛以去除任何较大的结块。称量空的称量舟并记录其质量。然后用药匙将少量粉末转移至称量舟中，并将其放在数字天平（读数至 0.01 g）上。记录你即将加入的粉末质量。
Step 3: Slowly add the pre‑weighed powder to the acid while the magnetic stirrer is running. Watch the indicator colour change. Continue adding more small portions of powder, recording the cumulative mass each time, until the indicator turns green, indicating a neutral pH (around 7). Stop adding powder immediately when the green colour appears.
步骤 3：在磁力搅拌器运行的同时，将已称重的粉末缓慢加入酸中。观察指示剂的颜色变化。继续加入少量粉末，每次记录累计质量，直到指示剂变为绿色，表明 pH 为中性（约 7）。当绿色出现时立即停止加入粉末。
Step 4: Record the total mass of powder used from the start to the green endpoint. This is the mass needed to neutralise 25.0 cm³ of acid for that trial. Rinse the flask thoroughly and repeat steps 2–4 for brand A twice more, to obtain three trials. Then repeat the entire process for brand B and brand C.
步骤 4：记录从开始到绿色终点所消耗的粉末总质量。这就是在该次试验中中和 25.0 cm³ 酸液所需的质量。彻底冲洗锥形瓶，并对品牌 A 重复步骤 2 至 4 两次，以获得三次试验。然后对品牌 B 和品牌 C 重复整个过程。
7. Recording Data | 记录数据
When recording results, it is important to use a neat table with clear headings and units. The raw data from the investigation are shown below. Each brand was tested three times to allow you to calculate a mean and to spot any anomalous readings.
记录结果时，使用带有清晰标题和单位的整洁表格非常重要。本次探究的原始数据如下所示。每个品牌均测试了三次，以便你能够计算出平均值并发现任何异常读数。
| Brand | Trial 1 (g) | Trial 2 (g) | Trial 3 (g) |
|---|---|---|---|
| A | 0.82 | 0.84 | 0.83 |
| B | 1.21 | 1.19 | 1.23 |
广告 / Sponsored 培生爱德思考试教材 统计数学3 Edexcel International A Level Mathematics S… 数学 备考教辅 · 正版现货 · 与本文内容相关 查看详情 / View on Taobao参考价 ¥156.0
更多咨询请联系16621398022（同微信） 备考资讯每日更新，关注不错过 考纲变化 · 科目分析 · 学习方法  在微信里长按二维码识别关注 或截图后用「扫一扫 → 相册」选择本图 公众号：tutorhao |