Why Combustion Releases Energy

Why combustion releases energy?

[2021-01-19]

From Schmidt-Rohr (2015):

“The double bond in $O_2$ is much weaker than other double bonds or pairs of single bonds, and therefore the formation of the stronger bonds in $CO_2$ and $H_{2}O$ results in the release of energy, which is given off as heat or increases thermal motion. This explains why fire is hot regardless of fuel composition. The bond energies in the fuel play only a minor role; for example, the total bond energy of $CH_4$ is nearly the same as that of $CO_2$.”

I have been used to thinking that breaking the strong bonds in fuel releases energy; however it’s the formation of the stronger bonds in the combustion products, i.e. $CO_2$ and $H_{2}O$ that releases energy. Energy is required to break the strong bonds between $CO_2$, it follows that generating the same bonds in $CO_2$ releases energy.