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Credits, from left: , Yan Luo, Yan Luo, Yan Luo |
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Safety:
IMPORTANT: Wear gloves and goggles at all times. The instructor should stay away from the reaction and students should be kept at least 1 m away from the demonstration. |
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Equipment:
- A 9V battery with both terminals on the same side (to complete the electric circuit)
- Recommended: objects made of iron or steel
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Materials:
A piece of fine steel wool (#0 or finer recommended) |
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Procedure:
- (Recommended) For Comparison: Touch different types of iron/steel-made objects (e.g. steel ruler, clamp, ring stand) by the terminals of a 9V battery. Show the students that both terminals of the battery are in touch with the object. (No physical change can be observed).
- Put a piece of fine steel wool (#0 or finer recommended, make into a loose sphere with ~1" radius) on an inflammable surface with no flammable objects near by (to prevent possible damage to surface).
- Touch the steel wool with a 9V battery. (The steel wool should start burning immediately).
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Notes:
What to observe: What is different when the same 9V battery is touching steel wool in Part 3 compared to other steel-made objects in Part 1? What causes the differences? Of the objects that were touched to the 9V battery, all of similar mass and made of steel, the steel wool has the largest surface area. More oxygen molecules are exposed to the steel surface in the steel wool, and therefore the energy provided by the 9V battery (which is not a lot) can only burn the steel wool but not the other objects. The chemical equation for the reaction is:  |
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Disposal:
Used batteries should be recycled or disposed properally. The steel wool may be thrown in the garbage as long as it has stopped burning. |
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