• Question: If you heated up a city to around 80 degrees celcius, and there were highly reactive metals like lithium (100g) sitting outside, would they explode? And if not, could it be possible at higher tempratures?

    Asked by mjones to Amy, Drew, Sara on 23 Jun 2011.
    • Photo: Amy MacQueen

      Amy MacQueen answered on 23 Jun 2011:

      Hi mjones!

      Ooooh I like this one! Well, you’d first have to hope the city didn’t have any rain that day or the lithium would have already reacted with it to form hydrogen gas and lithium hydroxide!! But pending a dry day you would next have th problem of heating the city (how are you going to do this?) …but say you COULD heat up the city are you heating the lithium (you said it was outside). If the lithium is inside the city but just outside a house or something then I would say that it won’t really do anything (it doesn’t melt until it is heated to 180oC).

      Oh also, cunning fact, lithium is used as a neutron absorber in nuclear fusion – this is how a lot of tritium is made which I work with!! 🙂

      So, although lithium is used in a lot of weaponry it is usually as its complex hydrides, such a Li[AlH4]. So I don’t think it would explode unless micxed with other stuff.

      But the other scientists can correct me if I’m wrong! 🙂

    • Photo: Drew Rae

      Drew Rae answered on 23 Jun 2011:

      Hi Mjones. Every element has an autoignition temperature at which they just catch fire when they are in a normal atmosphere. White Phosphorous for example will go up at around 34 degrees, which is why it is kept submerged.

      You’ve picked a good example in Lithium. Lithium batteries can be a real problem for autoignition. I’ve been trying to find out exactly what the autoignition point is for metalic lithium, but it doesn’t seem to be readily available. Lots of people quote the fact that it is below the temperature of a typical suppressed cargo fire in an airplane, but don’t say exactly what it is.

      So to answer your question, it’s a definite yes if the temperature is high enough, but exactly how high depends on exactly which metal.

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