When a reaction occurs where does the energy to cross the activation energy comes from?My book states that it might look like there is violation of conservation of energy but the physics of small particles is different.

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    $\begingroup$ Reactions occur in a heat bath of the solvent. The kinetic energy of the molecules vary, only is the average constant as determined by the temperature. Very occasionally, say one in a million collisions or less, by random events, is the collision of sufficient energy to overcome the activation barrier. $\endgroup$ – porphyrin May 26 '18 at 19:15

The energy to cross the activation energy doesn’t come out of nowhere. Many times it’s something like heat (which is basically how fast the particles are moving). For example, paper doesn’t combust to ash automatically[citation needed]. But heat it to 218 or so degrees centigrade, (including Fahrenheit 451) and it will auto ignite. This is due to the energy the heat provides.

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    $\begingroup$ That's just the title of the book not actual data. $\endgroup$ – Mithoron May 26 '18 at 20:52
  • $\begingroup$ @Mithoron it’s about between 218-240 centigrade, which includes 233 Celsius $\endgroup$ – JavaScriptCoder May 26 '18 at 22:39
  • $\begingroup$ @JavaScriptCoder: No offence to late Ray Bradbury, it was his idea when he named his famous book, Fahrenheit 451. However, the auto-ignition temperature of any solid material is a function of various factors including the time it expose to the high temperature. $\endgroup$ – Mathew Mahindaratne May 26 '18 at 23:23

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