why do some materials (paper, wood, butane, acetylene, gasoline, magnesium) burn at different temperatures?
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“Burning” refers to a chemical reaction where you take a large amount of complex molecules, make them react with oxygen and get them to release energy as they turn into simple molecules. This means that there’s several key temperatures at play.
The first temperature of “what something burns at” is based on how much energy is released. The vast majority of chemical bonds store some amount of energy – how much depends on structures, and what elements are in the bonds.
The second temperature of “what something burns at” is more around what temperature you need to get something to for it to burn. Imagine those bonds like a rubber band, stretched out with one hand gripping on one side and another gripping the other. If you pull hard enough on the band, it’ll snap and the energy stored in it goes everywhere – but it takes effort to pull it back and make it snap. That’s what happens with burning things. The bonds do eventually release energy, but they need to have energy pumped into them. That’s why you often need a spark, or some kind of extra heat (like fire next to the material releasing energy, causing it to spread). The three specific temperatures here are the flash point (where a spark hot enough to break some bonds causes an incredibly brief fire, as each broken bond doesn’t release enough energy to break more bonds and sustain the fire), the fire point (where a spark causes a sustained fire, as each broken bond releases enough energy to break more bonds) and the autoignition point (where you don’t need a spark, because the bonds have so much energy they break on their own).
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