Burning magnesium in dry ice


So, here’s a nice little demonstration you can do and it bridges the gap between an understanding of a reactivity series that contains only metals and one that contains non-metals as well. You’ll need some dry ice. You can obtain it from regular cryogenic or gas suppliers and it comes in 10 kilograms blocks like this. A regular wood saw will be able to cut through the block but you’ve got to be patient because they’re quite brittle. The last few centimetres will be hard going
but don’t rush it too quickly otherwise you may risk breaking the
block. Cut of a lid with an inch or so to play with and then chisel out a cavity into the body. Again, go easy with it
because you’ll likely fracture the block if you hit it with a chisel rather
than scraping it. Eventually you’ll end up with something
that looks a little bit like this. You can use these blocks more than once
so potentially you could actually team up with other teachers in the department
and run a series at these experiments on the same day. Let’s see what happens. Don’t be tempted to fill the cavity too high otherwise you can get sparks of magnesium that will fly out through the edge as you start to put the lid on. This experiment is being performed in fume cupboard because of restrictions where we filmed
it. At school it can be done in the open lab with a safety screen to protect
the audience who should be two to three metres away
and another screens protect yourself. The use of a blow torch was for convenience so a Bunsen will do just as well. As with any
demonstration before attempting it you should consult your employers risk assessment and consider
whether it needs any modification for special situation for the class or room. Dry ice should be handled with insulating gloves and goggles should be worn. Wearing a lab coat will reduce
the risk of burns from any burning magnesium that may be ejected. Never store dry ice in a sealed
container or use it in a confined space. It should not be transported in the passenger compartment of a car unless the windows are open. So there you have it magnesium and carbon dioxide, an unusual displacement reaction to show
how carbon fits into the reactivity series.

99 thoughts on “Burning magnesium in dry ice”

  1. Just trying to thank   Firebirdharris7 and Bill S for explaining what we are seeing here.
    Magnesium needs oxygen to burn. The dry ice (solid CO2/carbon dioxide) means that the environment the magnesium is in doesn't have diatomic oxygen (O2 which is what we breath and is just normal air oxygen) available to burn. What you are seeing is the magnesium taking the oxygen from the CO2 because magnesium is more reactive than carbon.  Bill S. observed,  black residue is carbon left after oxygen is consumed by Mg O2 reaction.   

  2. Dry ice is carbon dioxide. Carbon dioxide, by definition, contains oxygen. The magnesium isn't burning in the absence of oxygen; it's stealing the oxygen from the dry ice.

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  4. okay, two questions: Why is the dry ice not "melted" and how can the fire continue without oxygen? Doesn't the CO2 displace the oxygen in the chamber?

  5. How about doing the damn safety disclaimer first so you can explain wtf is going on here?  Yeah, I read the description but it would have been nice to have that explained while it was actually happening.

  6. Mmm… i guess that the flame excite an electron of the Mg, so we have a d-d transition that produce fluorescence when the electron returns to the fundamental state?

  7. "Don't rush it to quickly, or else you may risk breaking the block" he says as he then saws through it faster than I ever would! LOL

  8. It just goes to show that magnesium is far more reactive than carbon to the extend that it would "snatch" the oxygen from the CO2 molecule to form magnesium oxide at the high temperatures provided by the flame. All about relativity in the chemistry sense. Go vegan !

  9. Why not just use a Dremel tool with a 1 inch diameter carbide cutter bit. Or even just use your cordless drill with a cutter bit. way faster and easier to carve with.

  10. This video shows the science behind magnesium and carbon dioxide reaction.

    https://www.youtube.com/watch?v=BJCpsi5FrhE

  11. where do you get dry ice, where do you get magnesium, where do you get liquid nitrogen? guys if i ask one of these things they would hand me to police for terrorism 🙂

  12. Now what would happen if you lit magnesium ribbon under sand? Since silicon is an analogue of carbon I'd assume something fairly similar would happen

  13. Well the magnesium would snatch the oxygen from the CO2, similar to the way the thermite reaction snatches oxygen from iron oxide to give to aluminium.

  14. I was actually hoping the dry ice would start burning. I heard that hot Magnesium will form Magnesium oxide by stealing Oxygen from the CO2 bond. So the CO2 would be ignitable in that way.
    Does that not happen at all?

  15. I don't know why but hearing that saw cut thru that ice makes me cringe! I get chills running up and down my spine. I don't like it!

  16. "shouldn't be transported in a car" tell that to companies like Volkswagen where the engine block is made out of magnesium lol

  17. WRONG AGAIN. It's the oxygen being rippid away to firm magnesium oxide, leaving the carbon behind as a dark soot on it.

  18. So the point of this was…
    There's more cold in a block of dry ice than heat in a spoonful of burning magnesium?

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