📚 Year 8 SQA Chemistry: Case Study Practical Exercises | SQA Year 8 化学：案例分析实战演练
In SQA Year 8 Chemistry, applying knowledge to real-world situations is essential for developing scientific skills. This article presents a series of case study exercises designed to challenge you to think like a chemist, interpret data, and solve problems based on the Scottish Curriculum for Excellence at Third Level.
在SQA Year 8化学中，将知识应用于实际情境对于培养科学技能至关重要。本文提供一系列案例分析练习，旨在挑战你像化学家一样思考，解读数据，并基于苏格兰卓越课程第三级目标解决问题。
1. Case Study 1: Identifying Mystery Substances | 案例一：鉴定神秘物质
You are given two unlabelled white powders. Powder A dissolves in water and produces a gas when mixed with vinegar. Powder B does not dissolve in water and floats on the surface. Use your knowledge of chemical and physical properties to identify which might be baking soda and which might be chalk (calcium carbonate).
你拿到两种未贴标签的白色粉末。粉末A溶于水，与醋混合时产生气体。粉末B不溶于水且浮在水面。运用你对化学和物理性质的知识，判断哪一种是发酵粉（小苏打），哪一种是粉笔末（碳酸钙）。
First, recall that baking soda (sodium hydrogen carbonate, NaHCO₃) reacts with acids to release carbon dioxide gas. Chalk (CaCO₃) also reacts with acids but is insoluble in water.
首先，回忆小苏打（碳酸氢钠，NaHCO₃）与酸反应会释放二氧化碳气体。粉笔末（CaCO₃）也与酸反应，但不溶于水。
Observations show Powder A dissolves, so it is likely NaHCO₃, as it is soluble. Powder B is insoluble, so it fits CaCO₃. The reaction with vinegar would produce bubbles in both cases, but solubility is the key clue here.
观察显示粉末A溶解，因此很可能是NaHCO₃，因为它是可溶的。粉末B不溶，符合CaCO₃。两者与醋反应都会产生气泡，但溶解度是此处关键线索。
This case shows how a combination of solubility and acid reaction tests can identify common household compounds safely.
这个案例表明，通过结合溶解度测试和酸反应测试，可以安全地鉴别常见家用化合物。
2. Case Study 2: Acid Rain and Limestone | 案例二：酸雨与石灰石
Historic buildings made of limestone are being eroded by acid rain, which contains sulfuric acid. Explain the chemical change using a balanced word equation, and then translate it into symbols.
用硫酸构成的酸雨正在侵蚀石灰石建造的古建筑。请用文字方程式解释这一化学变化，再将其转化为符号方程式。
+ carbon dioxide + water. This is a neutralisation reaction where the carbonate base reacts with acid.
文字方程式为：碳酸钙 + 硫酸 → 硫酸钙 + 二氧化碳 + 水。这是一个中和反应，碳酸盐碱与酸反应。
CaCO₃ + H₂SO₄ → CaSO₄ + CO₂ + H₂O
CaCO₃ + H₂SO₄ → CaSO₄ + CO₂ + H₂O
Note that calcium sulfate is slightly soluble, which leads to gradual loss of stone as it washes away. This case illustrates the environmental impact of acid rain and the importance of reducing SO₂ emissions from industry.
注意硫酸钙微溶，会随着冲刷逐渐损失石料。此案例说明了酸雨的环境影响，以及减少工业二氧化硫排放的重要性。
3. Case Study 3: Separating a Mixture | 案例三：分离混合物
A mixture contains sand, salt, and iron filings. Design a step-by-step method to separate all three components, explaining the principle behind each step.
一种混合物含有沙子、食盐和铁屑。设计一套分步骤分离所有三种组分的方法，并解释每一步的原理。
Step 1: Use a magnet to attract the iron filings. Iron is magnetic, while sand and salt are not. This physical property allows quick separation.
步骤一：用磁铁吸引铁屑。铁有磁性，而沙子和食盐没有。利用这一物理性质可快速分离。
Step 2: Add the remaining mixture to water and stir. Salt dissolves in water, but sand does not. This exploits the difference in solubility.
步骤二：将剩余混合物加入水中搅拌。食盐溶于水，沙子不溶。这利用了溶解度的差异。
Step 3: Filter the mixture. The sand will be trapped on the filter paper as residue, while the salt solution (filtrate) passes through.
步骤三：过滤混合物。沙子会作为残渣留在滤纸上，而食盐溶液（滤液）则通过。
Step 4: Evaporate the water from the salt solution by gentle heating. Water boils off, leaving solid salt crystals behind.
步骤四：通过温和加热蒸发食盐溶液中的水。水蒸发后留下固态食盐晶体。
These separation techniques (magnetism, dissolving, filtration, evaporation) are fundamental in chemistry and mirror industrial processes.
这些分离技术（磁性分离、溶解、过滤、蒸发）是化学的基础，与工业流程相似。
4. Case Study 4: Rate of Reaction Investigation | 案例四：反应速率探究
A student investigates the effect of temperature on the reaction between magnesium ribbon and dilute hydrochloric acid. The volume of hydrogen gas produced in 30 seconds was recorded at three temperatures. Analyze the data and draw a conclusion.
一名学生探究温度对镁条与稀盐酸反应的影响。记录了在三种温度下30秒内产生的氢气体积。请分析数据并得出结论。
| Temperature / °C | Volume of H₂ in 30 s / cm³ |
|---|---|
| 20 | 12 |
| 30 | 23 |
| 40 | 38 |
The volume of hydrogen produced increases as temperature rises. This is because at higher temperatures, particles move faster and collide more frequently and with greater energy, so more successful collisions occur per second.
随着温度升高，产生的氢气体积增加。这是因为温度越高，粒子运动越快，碰撞更频繁且能量更大，因此每秒发生更多的有效碰撞。
To keep this test fair, the mass of magnesium, concentration and volume of acid must be kept constant. The independent variable is temperature; the dependent variable is gas volume.
为确保实验公平，镁的质量、酸的浓度和体积必须保持不变。自变量是温度；因变量是气体体积。
If you draw a graph, you can predict the volume at 50 °C using a line of best fit, showing the practical value of data analysis.
如果绘制图表，可以使用最佳拟合线预测50 °C时的气体体积，显示了数据分析的实际价值。
5. Case Study 5: Patterns in the Periodic Table | 案例五：元素周期表中的规律
A group of elements in Group 1 (alkali metals) react with water. The table below gives observations for lithium, sodium, and potassium. Use your knowledge of periodic trends to predict the reaction of rubidium, which is below potassium.
第1族（碱金属）中的一组元素与水反应。下表给出了锂、钠、钾的反应现象。利用周期律知识预测位于钾下方的铷的反应。
| Element | Observation with Water |
|---|---|
| Lithium (Li) | Fizzes steadily, moves on surface |
| Sodium (Na) | Melts into a ball, vigorous fizzing |
| Potassium (K) | Burns with a lilac flame, very vigorous |
As you go down Group 1, reactivity increases because the outer electron is further from the nucleus and more easily lost. Rubidium (Rb) is below potassium, so it will react even more violently, probably exploding with a flame and producing hydrogen gas instantly.
沿第1族向下，反应性增强，因为外层电子离原子核更远，更容易失去。铷（Rb）位于钾之下，因此反应会更剧烈，可能伴随火焰爆炸并立即产生氢气。
The trend can be explained by atomic structure: going down the group, the number of electron shells increases, weakening the attraction between the nucleus and the outermost electron.
这一趋势可用原子结构解释：沿族向下，电子层数增加，原子核与最外层电子间的吸引力减弱。
This case study reinforces how the periodic table helps predict properties of unfamiliar elements without experimenting directly.
这个案例强化了周期表如何帮助预测不熟悉元素的性质，无需直接实验。
6. Case Study 6: Neutralisation in Everyday Life | 案例六：生活中的中和反应
Stomach acid contains hydrochloric acid (HCl). Sometimes too much acid causes indigestion. Antacid tablets contain calcium carbonate (CaCO₃) or magnesium hydroxide (Mg(OH)₂). Explain how they relieve the pain using a neutralisation reaction.
胃酸含有盐酸（HCl）。有时胃酸过多引起消化不良。抗酸片含有碳酸钙（CaCO₃）或氢氧化镁（Mg(OH)₂）。解释它们是如何通过中和反应缓解疼痛的。
l → CaCl₂ + H₂O + CO₂. The acid is neutralised, forming a salt, water, and carbon dioxide.
当抗酸剂到达胃部，碱与酸反应。以碳酸钙为例：CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂。酸被中和，生成盐、水和二氧化碳。
OH)₂ + 2HCl → MgCl₂ + 2H₂O. No gas is produced, which some people prefer to avoid burping.
氢氧化镁中和盐酸：Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O。不产生气体，有些人为了避免打嗝会偏爱此类抗酸剂。
This case shows that neutralisation is not just a lab concept but a practical solution used in medicine.
这个案例表明，中和反应不仅是实验室概念，也是医学中使用的实际解决方案。
7. Case Study 7: Electrolysis of Water | 案例七：水的电解
Water can be split into hydrogen and oxygen gases using electricity. If you pass a direct current through acidified water, you collect twice the volume of hydrogen at the cathode as oxygen at the anode. Explain this result using the formula of water.
水可以用电分解成氢气和氧气。如果让直流电通过酸化水，在阴极收集到的氢气体积是阳极氧气体积的两倍。请用水的化学式解释这一结果。
2H₂O(l) → 2H₂(g) + O₂(g)
2H₂O(l) → 2H₂(g) + O₂(g)
The balanced equation shows that two molecules of water produce two molecules of hydrogen and one molecule of oxygen. Since equal volumes of gases at the same temperature and pressure contain the same number of molecules, the volume ratio H₂:O₂ is 2:1.
平衡方程式显示，两个水分子产生两个氢分子和一个氧分子。因为在相同温度和压力下，等体积气体含有相同数目的分子，所以氢气与氧气的体积比为2:1。
To make the water conduct electricity, a small amount of sulfuric acid is added, but the acid itself is not used up. This case illustrates the concept of electrolysis and the conservation of atoms.
为使水导电，加入少量硫酸，但酸本身不消耗。这个案例阐明了电解概念和原子守恒。
8. Case Study 8: Combustion and Environmental Impact | 案例八：燃烧与环境影响
Fossil fuels contain hydrocarbons. When a fuel burns completely, it produces carbon dioxide and water. Incomplete combustion can produce carbon monoxide and soot. Analyze the environmental consequences of these products and link to climate change.
化石燃料含有碳氢化合物。燃料完全燃烧时生成二氧化碳和水。不完全燃烧可能产生一氧化碳和碳烟。分析这些产物的环境后果，并与气候变化相联系。
CO₂ is a greenhouse gas that traps heat in the atmosphere, contributing to global warming.
甲烷的完全燃烧：CH₄ + 2O₂ → CO₂ + 2H₂O。多余的二氧化碳是一种温室气体，会把热量留在大气中，导致全球变暖。
CO + 4H₂O. Carbon monoxide is a poisonous gas that binds to haemoglobin, reducing oxygen transport in the blood. Soot (carbon particles) can cause respiratory problems and darken buildings.
不完全燃烧：2CH₄ + 3O₂ → 2CO + 4H₂O。一氧化碳是有毒气体，会与血红蛋白结合，降低血液输氧能力。碳烟（碳微粒）可引起呼吸道问题并使建筑物变黑。
Engineers design engines to run as close to complete combustion as possible by controlling the air-to-fuel ratio. This case shows how chemistry helps tackle real-world pollution challenges.
工程师通过控制空燃比，设计发动机尽可能接近完全燃烧。此案例展示了化学如何帮助应对现实世界的污染挑战。
9. Case Study 9: Safety in the Lab | 案例九：实验室安全
You are about to carry out a reaction that produces chlorine gas, which is toxic and irritating. Identify the hazard symbols you must look for on chemical bottles and list the precautions you should take.
你即将进行一个产生氯气的反应，氯气有毒且具有刺激性。识别化学试剂瓶上必须注意的危险标志，并列出应采取的安全措施。
The bottle of hydrochloric acid may show a corrosive symbol (test tube pouring on hand and surface) and an exclamation mark for irritant. Chlorine gas is produced, which requires a toxic symbol (skull and crossbones) and an environmental hazard symbol if released.
盐酸瓶可能显示腐蚀性标志（试管倒液在手上和表面）和感叹号刺激性标志。产生的氯气需要有毒标志（骷髅图）以及释放时的环境危害标志。
Precautions: work in a fume cupboard to vent gases safely; wear safety goggles and gloves; tie back long hair; and never mix chemicals unless instructed. Always read the risk assessment before starting.
安全措施：在通风橱中操作，安全排放气体；佩戴护目镜和手套；束起长发；未经指导不得混合化学品。开始前务必阅读风险评估。
Understanding hazard symbols and safe practices prevents accidents and ensures a safe learning environment for everyone.
了解危险标志和安全操作可防止事故，确保每个人的安全学习环境。
10. Case Study 10: Designing a Fair Test | 案例十：设计公平实验
Your task is to investigate whether the size of copper sulfate crystals affects how quickly they dissolve in water. Write a plan that identifies the independent, dependent, and control variables, and describe how to collect reliable data.
你的任务是探究硫酸铜晶体的大小是否影响它们在水中的溶解速度。写一份计划，确定自变量、因变量和控制变量，并描述如何收集可靠数据。
Independent variable: crystal size (e.g., large crystals vs. fine powder). Dependent variable: time taken for the blue colour to disappear or for the solid to fully dissolve. Control variables: volume of water, water temperature, stirring speed, and mass of copper sulfate used.
自变量：晶体大小（例如大晶体与细粉末）。因变量：蓝色消失或固体完全溶解所需时间。控制变量：水的体积、水温、搅拌速度和所用硫酸铜的质量。
Method: measure 100 cm³ of water at room temperature (20 °C) into a beaker. Use the same mass, e.g., 5 g of copper sulfate in each trial. Start the stopwatch the moment you add the crystals and stir at a constant rate. Record the time until no solid remains. Repeat three times for each crystal size to improve reliability and calculate a mean.
方法：用量筒量取100 cm³室温（20 °C）水倒入烧杯。每次试验使用相同质量，例如5 g硫酸铜。在加入晶体的瞬间启动秒表并以恒定速率搅拌。记录直至固体消失的时间。每种晶体大小重复三次以提高可靠性并计算平均值。
This investigation connects particle theory: smaller crystals have a larger surface area exposed to water, so more particles collide with water molecules per second, increasing the rate of dissolving.
此探究联系粒子理论：较小晶体的表面积更大，与水接触面积更多，因此每秒与水分子碰撞的粒子更多，加快溶解速率。
'Fair testing' is a core skill in science, ensuring that any change in the dependent variable is truly caused by the independent variable alone.
'公平实验'是科学的核心技能，确保因变量的任何变化确实仅由自变量引起。
Published by TutorHao | Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图