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I'm so curious about fire. So I searched a lot in the internet. And now, I knew that fire is some kind of chain reaction and combustion energy make the other molecule hot and the other molecule makes other chemical reaction and so on... Then does the first given energy make this reaction start and maintain chemical reaction(fire)? if so, if a long time passes, fire goes out? and how much energy is needed to make this chain reaction start?

to sum it up,

  1. when cigarette lighter make candlelight start how much energy is needed?
  2. if a long time passes, this candlelight goes out? (Assuming that oxygen and material(will be burned) are supplied)

  3. how much energy go out with light or heat?

(I'm not good at english, so please understand me)

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The first given energy is called the activation energy. The chemical reactions of burning liberate energy in the form of heat and light (and probably some sound), and a small part of that energy activates further combustion. The amount of activation energy required to start the fire depends on what you're burning.

In your example, once the candle is alight, the bit of the candle that is currently burning provides the activation energy for the next part of the candle.

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    $\begingroup$ And a pyrophoric substance doesn’t need any activation energy above random thermal energy... $\endgroup$ – Jon Custer May 28 at 13:34
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The amount of energy needed to start a fire depends on the combustibility of the substrate. The energy supplied needs to be enough to heat a small quantity of the material to its ignition temperature. If it is something highly inflammable like methane,hydrogen or aviation spirit,a tiny, almost invisible spark is enough to do the trick.a spark of static electricity for instance. For something less combustible,like wood or coal,a lot more energy is required to heat it to ignition temperature & maintain that temperature till it is well ablaze.

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