ドライアイス中でのマグネシウムの燃焼

マグネシウムが固体二酸化炭素の中で燃え続け、CO₂を炭素に還元する

Classroom Demonstrations Advanced (University) 25 分 ~$15.00

目的

マグネシウムが二酸化炭素を還元できることを実証し、CO₂が常に火を消すという誤概念を払拭する。

背景

Magnesium burns so intensely (over 3000°C) that it can reduce carbon dioxide to elemental carbon. When a burning magnesium ribbon is placed in a cavity carved into dry ice (solid CO₂), it continues to burn brilliantly white, producing magnesium oxide (white powder) and elemental carbon (black specks). This reaction (2Mg + CO₂ → 2MgO + C) dramatically shows that CO₂ is not always an effective fire extinguisher and that thermodynamic favorability depends on the specific reactants involved.

安全上の警告

  • Burning magnesium is extremely bright — never look directly at it without shade protection
  • Dry ice causes frostbite on contact — never handle with bare hands
  • Perform behind a safety shield
  • Keep a fire-resistant mat underneath
  • Do not attempt to extinguish burning Mg with water — explosion risk
  • Ensure ventilation — CO₂ accumulation in enclosed spaces is dangerous

必要なPPE

goggles gloves lab_coat face_shield

材料

  • Magnesium ribbon (30 cm)
    Clean, bright surface
  • Dry ice block (1 kg)
    Solid CO₂ (−78.5°C)
  • Tongs (long-handled) (1)
    For handling dry ice

器具

Safety shield Fire-resistant mat Chisel or screwdriver (for carving cavity in dry ice) Lighter or matches Welding goggles or #14 shade glass

手順

1

Using tongs, carve a small cavity (about 3 cm deep) in the dry ice block. Place the dry ice on a fire-resistant mat.

3 分 Wear insulated gloves for dry ice
2

Set up the safety shield between the demonstration and the audience. Distribute welding goggles or instruct everyone to look away when ignited.

2 分
3

Light one end of the magnesium ribbon. Once burning, quickly place it in the dry ice cavity using tongs.

2 分 Do not look directly at the flame
4

Place another piece of dry ice on top to create a CO₂ atmosphere around the burning magnesium.

2 分
5

Observe: the magnesium continues to burn with an intense white flame inside the CO₂ environment. It does NOT go out.

3 分 Maintain safe distance
6

After the reaction, examine the residue: white MgO powder and black carbon specks. Discuss the reaction: 2Mg + CO₂ → 2MgO + C.

8 分 Wait for residue to cool completely
7

Discuss implications for fire safety: why Mg fires cannot be extinguished with CO₂, water, or standard fire extinguishers.

5 分

予想される結果

The magnesium continues to burn brilliantly inside the dry ice. After the reaction, white MgO and black carbon specks are visible in the dry ice cavity. This proves CO₂ has been reduced to elemental carbon.

後片付け

Allow all residues to cool and dry ice to sublimate. Sweep up MgO and carbon residue. No chemical waste disposal needed.

詳細

カテゴリ
Classroom Demonstrations
難易度
Advanced (University)
所要時間
25 分
推定費用
$15.00
ステップ数
7
材料
3

その他の実験

テルミット反応 30 min ナトリウムと水の反応 25 min ヨウ素時計反応 45 min ルミノールによる化学発光 30 min 密度カラム虹 30 min 振動するブリッグス-ラウシャー反応 40 min 消えるビーカー（屈折率マッチング） 15 min 瞬間凍結：過冷却水 120 min 象の歯磨き粉 20 min 非ニュートン流体：ウブレック 20 min

Frequently Asked Questions

What is the objective of ドライアイス中でのマグネシウムの燃焼?
マグネシウムが二酸化炭素を還元できることを実証し、CO₂が常に火を消すという誤概念を払拭する。
How difficult is ドライアイス中でのマグネシウムの燃焼?
This experiment is rated as Advanced (University). It takes approximately 25 minutes to complete.
What safety precautions are needed for ドライアイス中でのマグネシウムの燃焼?
Key safety precautions include: Burning magnesium is extremely bright — never look directly at it without shade protection; Dry ice causes frostbite on contact — never handle with bare hands; Perform behind a safety shield.
What materials are needed for ドライアイス中でのマグネシウムの燃焼?
The main materials required are: Magnesium ribbon, Dry ice block, Tongs (long-handled).
What results should I expect from ドライアイス中でのマグネシウムの燃焼?
The magnesium continues to burn brilliantly inside the dry ice. After the reaction, white MgO and black carbon specks are visible in the dry ice cavity. This proves CO₂ has been reduced to elemental carbon.