📚 Year 10 CIE Chemistry: Case Study Practical Drills | CIE 十年级化学：案例分析实战演练
Welcome to this intensive revision article that turns core CIE Year 10 chemistry topics into real-world case studies. By working through scenarios like aluminium extraction, water purification, catalytic converters, reaction rate investigations, and fuel cells, you will learn to apply concepts such as electrolysis, environmental chemistry, collision theory, and energy changes.
欢迎阅读这篇强化复习文章，它将 CIE 十年级化学的核心主题转化为真实世界的案例分析。通过铝的提取、水的净化、催化转化器、反应速率探究和燃料电池等情景，你将学会运用电解、环境化学、碰撞理论和能量变化等概念。
1. Case Background: Bauxite and the Bayer Process | 案例背景：铝土矿与拜耳法
Bauxite is the main ore of aluminium, consisting of aluminium oxide (Al₂O₃) along with iron(III) oxide, silica and other impurities.
铝土矿是铝的主要矿石，主要成分为氧化铝 (Al₂O₃)，伴生有氧化铁、二氧化硅等杂质。
The Bayer process begins by crushing the bauxite and treating it with hot, concentrated sodium hydroxide (NaOH). The amphoteric Al₂O₃ dissolves to form soluble sodium aluminate (NaAlO₂ or NaAl(OH)₄), while impurities like iron oxides remain solid and are filtered off.
拜耳法首先将铝土矿粉碎，然后用热的浓氢氧化钠 (NaOH) 处理。具有两性的氧化铝溶解生成可溶的铝酸钠 (NaAlO₂ 或 NaAl(OH)₄)，而氧化铁等杂质仍为固态，被过滤除去。
After cooling, aluminium hydroxide Al(OH)₃ precipitates, which is then heated to produce pure alumina.
冷却后，氢氧化铝 Al(OH)₃ 沉淀析出，经加热得到纯氧化铝。
Al₂O₃ (in bauxite) + 2NaOH + 3H₂O → 2NaAl(OH)₄
2Al(OH)₃ → Al₂O₃ + 3H₂O
2. Electrolysis of Alumina and the Role of Cryolite | 氧化铝的电解与冰晶石的作用
Pure alumina has a very high melting point (about 2050 ℃), making direct melting impractical. Instead, it is dissolved in molten cryolite (Na₃AlF₆), reducing the operating temperature to about 950 ℃, which saves energy and costs.
纯氧化铝的熔点极高（约 2050 ℃），直接熔化不切实际。工业上将其溶于熔融的冰晶石 (Na₃AlF₆) 中，操作温度降至约 950 ℃，既节省能源又降低成本。
The electrolysis cell uses a graphite anode and a carbon-lined cathode. At the cathode, aluminium ions are reduced:
电解在碳衬里的钢制电解槽中进行。石墨阳极浸入电解质中。阴极反应是铝离子被还原：
Cathode: Al³⁺ + 3e⁻ → Al (liquid)
At the anode, oxide ions are oxidised:
阳极处，氧化物离子被氧化：
Anode: 2O²⁻ → O₂ + 4e⁻
The overall reaction is:
总反应为：
2Al₂O₃ → 4Al + 3O₂
The oxygen produced at the anode reacts with the carbon anodes, forming CO₂ and gradually burning them away, so anodes need regular replacement.
阳极生成的氧气与石墨阳极反应生成 CO₂，使阳极逐步消耗，因此阳极需定期更换。
3. Environmental Impact and Recycling of Aluminium | 环境影响与铝的回收
Aluminium extraction is energy-intensive, consuming around 15 kWh of electricity per kilogram of aluminium. The high carbon footprint, coupled with anode consumption and greenhouse gas emissions, presents significant environmental challenges.
铝的提取能耗巨大，每千克铝约耗电 15 千瓦时。高碳足迹、阳极消耗以及温室气体排放构成了重大的环境挑战。
Recycling aluminium uses only about 5% of the energy needed for primary extraction. Scrap aluminium is melted and re-formed, which avoids the electrolysis step and greatly reduces pollution.
回收铝仅需原生提取约 5% 的能量。废铝熔融后重新成型，省去了电解步骤，大幅降低污染。
In a case study scenario, students might be asked to calculate energy savings or discuss why recycling is economically and environmentally preferable.
在案例分析中，学生可能需要计算能量节约量，或论述回收铝为何在经济和环境上更可取。
4. Hard Water: Causes and Consequences | 硬水：成因与影响
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