铝热反应

从铁锈和铝中产生熔融铁的极放热氧化还原反应

Classroom Demonstrations Advanced (University) 30 分钟 ~$15.00

目标

演示铝将氧化铁还原为熔融铁的极端放热氧化还原反应。

背景

The thermite reaction (2Al + Fe₂O₃ → Al₂O₃ + 2Fe) is one of the most exothermic chemical reactions known. Aluminum reduces iron(III) oxide to produce molten iron and aluminum oxide, reaching temperatures above 2500°C. The reaction is driven by the much greater affinity of aluminum for oxygen compared to iron (the activity series in dramatic action). Thermite is used industrially for welding railroad tracks and cutting through steel.

安全警告

  • EXTREME CAUTION: Reaction produces temperatures above 2500°C
  • Perform OUTDOORS ONLY with at least 10 m clearance
  • Molten iron droplets are ejected — no one within 5 meters
  • Heavy-duty safety shield is mandatory
  • Have a Class D fire extinguisher on hand (not water or CO₂)
  • Aluminum powder is an explosion hazard — keep away from flame until ready
  • Never attempt to move or disturb the reaction once ignited
  • Wait at least 30 minutes for products to cool before approaching

所需PPE

goggles gloves lab_coat face_shield

材料

  • Iron(III) oxide (Fe₂O₃) powder (50 g)
    Fine rust powder
  • Aluminum powder (15 g)
    Fine mesh (200+)
  • Magnesium ribbon (20 cm)
    Ignition fuse
  • Sand (5 kg)
    Insulation bed

设备

Clay flower pot (with drainage hole plugged) Ring stand with iron ring Metal bucket filled with dry sand Safety shield (heavy duty) Fire extinguisher (Class D) Long-handled lighter or match holder

步骤

1

OUTDOORS ONLY: Set up the ring stand over the sand-filled bucket. Place the clay pot (with drainage hole plugged with a small wad of paper) on the iron ring.

5 分钟 10 m minimum clearance from buildings
2

Mix 50 g Fe₂O₃ with 15 g Al powder thoroughly (by weight, approximately 3:1 ratio) in the clay pot.

3 分钟 No open flames near Al powder
3

Insert the magnesium ribbon into the top of the mixture as a fuse. Ensure the shield is positioned correctly.

2 分钟
4

Ensure all observers are at least 5 meters away and behind cover. Light the magnesium ribbon with a long lighter and retreat immediately.

2 分钟 RETREAT IMMEDIATELY after igniting
5

Observe from safe distance: the reaction produces an intensely bright white-orange glow and sparks. Molten iron drips through the pot into the sand below.

3 分钟 Do not look directly at the reaction without eye protection
6

Wait at least 30 minutes for everything to cool. Dig through the sand to find the solidified iron button.

10 分钟 Products may still be very hot
7

Examine the iron button and white Al₂O₃ slag. Discuss: activity series, enthalpy of formation, why Al is used in thermite (high affinity for O₂), and industrial applications.

5 分钟

预期结果

An intensely bright, self-sustaining reaction lasting 10–20 seconds. Molten iron collects at the bottom (a solid metal button when cooled). White Al₂O₃ slag forms on top. The reaction demonstrates the extreme energy difference between Al-O and Fe-O bonds.

清理

Once fully cooled, collect the iron button and slag. Sand can be reused. Do not pour water on hot products. Dispose of residue in general waste.

详情

类别
Classroom Demonstrations
难度
Advanced (University)
时长
30 分钟
预估费用
$15.00
步骤数
7
材料
4

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Frequently Asked Questions

What is the objective of 铝热反应?
演示铝将氧化铁还原为熔融铁的极端放热氧化还原反应。
How difficult is 铝热反应?
This experiment is rated as Advanced (University). It takes approximately 30 minutes to complete.
What safety precautions are needed for 铝热反应?
Key safety precautions include: EXTREME CAUTION: Reaction produces temperatures above 2500°C; Perform OUTDOORS ONLY with at least 10 m clearance; Molten iron droplets are ejected — no one within 5 meters.
What materials are needed for 铝热反应?
The main materials required are: Iron(III) oxide (Fe₂O₃) powder, Aluminum powder, Magnesium ribbon, Sand.
What results should I expect from 铝热反应?
An intensely bright, self-sustaining reaction lasting 10–20 seconds. Molten iron collects at the bottom (a solid metal button when cooled). White Al₂O₃ slag forms on top. The reaction demonstrates the extreme energy difference between Al-O and Fe-O bonds.