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Q & A: Burning Magnesium

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Q:
why does magnesium burn so hard, fast and hot ?
- mathew (age 15)
A:
Great question Mathew -

Atoms have a positive nucleus with just enough negative electrons "roaming " around it to just balance the charge. Oxygens in the air have a strong affinity for extra electrons and magnesium atoms can readily give up electrons. The reaction gives Mg2+ ions and O2- ions which are strongly attracted to each other to form MgO, thus giving off lots of energy.

(republished on 07/24/06)

Follow-Up #1: Water on a magnesium fire? Bad advice

Q:
Why can't you use water or a fire extinguisher to extinguish a magnesium fire?
- shannon (age 15)
San Antonio, TX, USA
A:
It's because magnesium eats water for breakfast and makes the fire stronger.
Seriously, there is a reaction Mg (s) + 2H2O --> Mg(OH)2 + H2 that produces hydrogen gas.  This hydrogen then burns by combining with oxygen in the air and makes the fire hotter.
See: http://www.lenntech.com/periodic/water/magnesium/magnesium-and-water.htm

LeeH

(published on 11/17/09)

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