GoKawiilWhen two rusty iron balls—one wrapped in aluminum foil—are struck together, sparks and light are given off in this small scale thermite reaction.
Video of Microscope Thermite Reaction can be found at https://www.youtube.com/watch?v=V5VXt0hZOc8
What it Shows
This is a much safer, microscale version of the thermite reaction—very fun and easy to perform! The classic thermite reaction is a spectacular oxidation-reduction reaction that takes place when aluminum metal is reacted with rust, Fe 2 O 3 .
2Al(s) + Fe 2 O 3 (s) → Al 2 O 3 (s) + 2Fe(s) + heat
In this version, two rusty iron balls, approximately 2 kg each and 7 cm in diameter, are struck together with a glancing blow.
The mechanical energy of the balls colliding provides enough activation energy to allow the reaction to occur, resulting in the formation of the products and large amounts of heat. There is a loud noise and flying sparks that occur due to the large amount of thermal energy released in the reaction.
How it Works
The classic thermite reaction is an energetic oxidation-reduction reaction where aluminum is oxidized and iron is reduced, according to the equation above. This highly exothermic single replacement reaction is so energetic that it is used to weld railroad tracks together. Variations of the reaction are also used in underwater welding. Once the reaction starts, it is self-sustaining and does not depend on an external supply of oxygen. A video of the large scale version can be viewed here.
The heat of reaction is ΔH° = -849 kJ/mol, resulting in a reaction temperature of approximately 2200 °C. This is hot enough to melt the iron produced, which has a melting point of 1530 °C. The bright yellow sparks result from microscopic amounts of extremely hot molten iron being thrown out into the air. The molten iron immediately oxidizes with the oxygen in the air, producing additional energy. The yellow color of the sparks is caused by the emission of light following the excitation of electrons in iron atoms. There is also a loud cracking sound when the reaction takes place that is not just the sound of the impact.
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