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HKDSE Chemistry – Planet Earth

HKDSE Chemistry Core
Section 1: Planet Earth | 地球

Billy Sir’s Smart Notes: Master Fundamentals of Chemistry, Separation Techniques, and the Environment.
由資深導師 Billy Sir 編寫，助你極速掌握化學基礎、分離技術及地球環境化學。

1. Classification of Matter & Changes | 物質的分類與變化

Matter can be classified into elements, compounds, and mixtures. 物質可分為元素、化合物和混合物。

Type (類別) Definition (定義) Examples (例子)
Element
元素		 A pure substance that cannot be broken down into simpler substances.
不能分解為更簡單物質的純淨物。		 \( \text{O}_2 \), \( \text{Fe} \)
Compound
化合物		 A pure substance made of two or more elements chemically combined.
由兩種或以上元素經化學結合而成的純淨物。		 \( \text{H}_2\text{O} \), \( \text{NaCl} \)
Mixture
混合物		 Two or more substances physically mixed together but not chemically combined.
兩種或以上物質物理混合，無化學結合。		 Air (空氣), Sea water (海水)

🔄 Physical vs Chemical Changes | 物理變化 vs 化學變化

  • Physical Change (物理變化): No new substance is formed (e.g., melting of ice, dissolving salt in water). 沒有新物質生成（例如：冰融化、鹽溶於水）。
  • Chemical Change (化學變化): One or more new substances are formed (e.g., burning of wood, rusting of iron). 有一種或多種新物質生成（例如：木材燃燒、鐵生鏽）。

2. Lab Safety & Bunsen Burner | 實驗室安全與本生燈

Common Hazard Warning Labels (常見危險警告標籤): Flammable (易燃), Toxic (有毒), Corrosive (腐蝕性), Explosive (爆炸性), Irritant (刺激性). 在實驗室中，必須認清化學品上的警告標籤以確保安全。

🔥 Steps to Turn On a Bunsen Burner | 點燃本生燈的步驟

Always follow these steps strictly to prevent accidents! 必須嚴格遵守以下步驟以防意外！

  1. Close the air hole completely. (完全關閉氣孔。)
  2. Light a match and hold it just above the chimney. (點燃火柴，放在煙囪頂部上方。)
  3. Turn on the gas tap. A yellow luminous flame will appear. (開啟煤氣掣，會出現黃色發光火焰。)
  4. Open the air hole slowly to obtain a blue non-luminous flame (for heating). (慢慢打開氣孔，以獲得用於加熱的藍色無光火焰。)

3. The Atmosphere | 大氣層

Air is a mixture of gases. Its approximate composition by volume is: 空氣是氣體的混合物，其體積百分比大約為：

  • Nitrogen (\( \text{N}_2 \)): 78%
  • Oxygen (\( \text{O}_2 \)): 21%
  • Argon (Noble Gas) (\( \text{Ar} \)): 0.9%
  • Carbon Dioxide (\( \text{CO}_2 \)): 0.04%

🏭 Fractional Distillation of Liquefied Air | 液態空氣的分餾

Air can be separated into its components by fractional distillation because different gases have different boiling points. 空氣可透過分餾分離，因為不同的氣體具有不同的沸點。

Air is first purified, compressed, and cooled into a liquid. When warmed, gases boil off in order of their boiling points (lowest boiling point boils off first: Nitrogen -> Argon -> Oxygen). (空氣先被淨化、壓縮並冷卻成液體。加熱時，氣體按沸點順序沸騰釋出：氮氣 -> 氬氣 -> 氧氣。)

4. Sea Water & Separation Techniques | 海水與分離技術

Sea water is an aqueous solution containing dissolved salts. 海水是含有溶解鹽類的水溶液。

  • Solute (溶質): The substance that dissolves (e.g., Salt). (被溶解的物質，如鹽。)
  • Solvent (溶劑): The liquid in which the solute dissolves (e.g., Water). (溶解溶質的液體，如水。)
  • Solution (溶液): The mixture formed (e.g., Sea water). (形成的混合物，如海水。)
Method (方法) Evaporation (蒸發) Crystallization (結晶)
Process
過程		 Heat the solution until all solvent boils away.
加熱溶液直到所有溶劑沸騰揮發。		 Heat to concentrate, then cool down to let crystals form.
加熱濃縮，然後冷卻讓晶體形成。
Result
結果		 Obtain a powder (may contain impurities).
獲得粉末（可能含有雜質）。		 Obtain pure, large crystals.
獲得純淨的大晶體。

🧪 Chemical Tests | 化學測試

  • Flame Test (焰色測試): Tests for metal cations. Sodium ion (\( \text{Na}^+ \)) gives a golden yellow flame. (測試金屬陽離子。鈉離子呈金黃色火焰。)
  • Silver Nitrate Test (硝酸銀測試): Tests for chloride ions (\( \text{Cl}^- \)). Adding acidified \( \text{AgNO}_3(\text{aq}) \) to sea water forms a white precipitate of Silver Chloride (\( \text{AgCl} \)). (測試氯離子。加入酸化的硝酸銀會產生氯化銀的白色沉澱物。)
  • Water Test (水測試): Pure water turns anhydrous copper(II) sulfate from white to blue, OR turns dry cobalt(II) chloride paper from blue to pink. (純水能使無水硫酸銅(II)由白變藍，或使乾燥的氯化鈷(II)試紙由藍變粉紅。)

5. Rocks and the Calcium Carbonate Cycle | 岩石與碳酸鈣循環

Limestone, chalk, and marble are mainly composed of Calcium Carbonate (\( \text{CaCO}_3 \)). 石灰石、粉筆和大理石主要由碳酸鈣組成。

🔄 The Calcium Carbonate Cycle | 碳酸鈣循環

  1. Heating Limestone: \( \text{CaCO}_3(\text{s}) \rightarrow \text{CaO}(\text{s}) + \text{CO}_2(\text{g}) \)
    (Produces Quicklime / 生石灰)
  2. Adding Water to Quicklime: \( \text{CaO}(\text{s}) + \text{H}_2\text{O}(\text{l}) \rightarrow \text{Ca(OH)}_2(\text{s}) \)
    (Produces Slaked lime / 熟石灰)
  3. Dissolving in excess water: \( \text{Ca(OH)}_2(\text{s}) + \text{water} \rightarrow \text{Ca(OH)}_2(\text{aq}) \)
    (Produces Limewater / 石灰水)
  4. Testing for \( \text{CO}_2 \): \( \text{Ca(OH)}_2(\text{aq}) + \text{CO}_2(\text{g}) \rightarrow \text{CaCO}_3(\text{s}) + \text{H}_2\text{O}(\text{l}) \)
    (Limewater turns milky due to insoluble \( \text{CaCO}_3 \) / 石灰水變乳濁)

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