Before my trip to Australia I got some magnesium—and by before my trip, I mean the day of. Emory, the university where I work, didn’t have any, so I went to Georgia Tech. I bought magnesium in its powder form. It’s just as fun as the strips, but messier! During my tour down under, I did demos with the powder, but when I got back I still had half a bottle left. We put it to good use in this experiment!
Magnesium, the twelfth element, is an alkaline earth metal (group II) and is represented in 2% of the earth’s crust. Though this experiment highlights magnesium powder’s flammability, it should be noted that magnesium, in bulk, is not very flammable. As we learned in our nondairy creamer experiment, powders have a propensity for combustion. Bulk magnesium is popular in industry for its strength and overall lightness (magnesium is 33% lighter than aluminum). Many car companies (such as BMW) use magnesium to make their engine blocks. Other industrial uses for magnesium are hinged on its ability to produce copious amounts of heat when burnt.
Our experiment was also based on burning magnesium. Magnesium burns at 2200ºC or roughly 4000ºF, and produces a bright white light (look at the spots of burning magnesium in the picture below):
Magnesium produces white light because when its excited electrons fall back to their ground state, they release energy encompassing all of the Balmer series (i.e. visible light). Because every wavelength of light is produced, the human eye sees this as one single net result, white light. However, when we were cleaning our tools after the experiment we noticed that they were a bit dirty. The results are quite beautiful:
In school laboratories burning magnesium is often demonstrated using magnesium strips. The reason strips are used being that magnesium will only burn in small (thin) quantities or in powder form, and that using powder—as we discovered—can be both messy and dangerous. We did our experiment in what can be described as a very thick steel bowl. We used a butane torch to heat corners of the bowl, and then blow powder onto the hot surface. We then used hot magnesium to ignite the rest. The result was a bowl full of unburnt magnesium, burning magnesium, and magnesium oxide (the result of combustion, a white powder). It should also be noted that magnesium powder will not burn with a match or lighter. At best there is occasionally a spark. So, to keep you safe and sound, we recommend that you admire these videos and keep away from the powder!
Funny/Dangerous Note: This lab isn't the safest because of the temperatures involved. We found this out first hand when we accidently blew some of burning magnesium out of the steel plate, and onto Joost's wooden workbench. Needless to say, we moved outside after that, but there were quite a few ashes flying around his garage. This brings me to a side note. If you ever start a magnesium fire, never put it out with water or a C02 extinguisher. Water will only feed the fire. This is because water will instantly vaporize when it touches the fire and will produce magnesium hydroxide:
Mg + 2 H2O → Mg(OH)2 + H2
SInce magnesium can burn in carbon dioxide, one should only use a class D fire extinguisher (see our post about fire extinguishers) or sand or baking powder. Now with that asidem here is a video of the famous fire, and then our new spot outside:
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