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I am trying to clarify this for Class 8 Science. Their textbook says "It is the lowest temperature at which a substance catches fire". However, it does not clarify whether it is on its own or due to an external source. I read through various websites and there are both kinds of definitions put up! Some also mentioned a flash point. So wanted to know what the proper definition of ignition temperature is and how it differs from flash point. Thanks!

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From Wikipedia:

Autoignition Temperature: the lowest temperature at which a substance spontaneously ignites without a source of ignition (such as a flame or spark).

Flash Point: the lowest temperature at which the vapours of a (volatile) material will ignite, with an ignition source.

Ignition temperature means the same thing as autoignition temperature according to Merriam Webster.

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    $\begingroup$ The question talks about "ignition temperature", not "autoignition temperature". To be a reasonable answer to the question, you would have to demonstrate that "ignition temperature" is almost certainly a mis-reading of "autoignition temperature." (i.e. that "ignition temperature" isn't a thing distinct from "autoignition temperature".) $\endgroup$ – R.M. Sep 18 '17 at 14:43
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    $\begingroup$ @R.M. The resolution might be the frequent use of overly casual language. Many people might causally say "ignition temperature" when they mean autoignition temperature. $\endgroup$ – matt_black Sep 18 '17 at 19:44
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    $\begingroup$ I always heard the two used interchangeably, and figured the second one was shortened for ease of speech. $\endgroup$ – SCH Sep 18 '17 at 22:23

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