PeriodicExperiments: #12: Burning Magnesium in Carbon Dioxide

If you have ever stared into a fireplace or campfire chances are you have pondered a particular question. That being, what is fire? Technically, most fire is a plasma-like portion of semi-ionized gas. However, what most people really want to know is what it means for something to burn? The answer is somewhat simple. Burning, or combustion, happens when a substance has enough energy to oxidize. In other words, materials burn because they want to bond with oxygen. I explored this interesting concept in an experiment that I performed recently.

To start, I filled two identical flasks with vinegar (dilute acetic acid [C2H4O2]) and baking soda (sodium bicarbonate [NaHCO3]). The reaction that took place produced a nice amount of carbon dioxide (CO2). After corking the containers, I was ready to perform two tests. For the first part, I simply lit a large match and held it over one of the flasks. Instantly, it was snuffed out. In my second test, I ignited a strip of magnesium metal and suspended it within the other flask of gas. Unlike the wooden match, the magnesium continued to blaze brightly until it was completely consumed. To explain these differing results, I looked at the science.

In the case of the lit match, I knew that it ran out of oxygen upon entering the CO2. The question was, why didn't the same thing happen to the magnesium? The answer lies in the fact that magnesium burns with an extremely high amount of energy. In other words, the metal has a very powerful attraction to oxygen and will try incredibly hard to bond with it. It is because of this extreme desire that magnesium is able to rip oxygen atoms straight off of other molecules. Thus, I concluded that, when placed in the flask, the burning magnesium obtained all of its oxygen from the carbon dioxide. I found that to be particularly remarkable.