How is chemical energy released?

   Chemical energy is released when atoms react with other atoms. Generally energy is released as heat (i.e., kinetic energy of atoms) and light; for example oxidation of hydrocarbons, reaction between hydrogen and oxygen etc. One of the interesting facts is that most chemical reactions that release heat energy produce water molecules which are one of the strongly bonded molecules found in nature. When hydrocarbons burn in the air it produces water molecules (H₂O) and carbon compounds like carbon dioxide (CO₂) and carbon monoxide (CO) etc. In these other than water molecule, CO2 is another strongly bonded molecule found in nature. Now see below the relationship between bond length and bond energy of carbon-oxygen bonds and nitrogen-nitrogen bonds.

   Here we can find an important relationship between bond length and bond energy. i.e., as bond length decreases there is a steady increase in bond energy. For example the bond length of a single bond nitrogen molecule is 0.145nm, its bond energy is 159kJ/mol. The bond length of a double bond nitrogen molecule is 0.125nm; its bond energy is 473kJ/mol. The bond length of a triple bond nitrogen molecule is 0.110nm; but its bond energy is 941kJ/mol (this is the strongest molecule found in nature).
   Now the question is how exactly chemical energy is released? New studies indicate that the nucleus of an atom is enveloped by a form of matter called space matter (see structure of atom). We can see that the volume of any molecule is less than the sum of the separate volume of its containing atoms. When atoms bond in a molecular formation they will overlap each other. This overlapping between atoms causes release of overlapped volume of space matter. Because the space matter is in compressed state in atoms when it is released it will expand and explode. From this fast expansion of space matter, the product molecules get kinetic energy and act as projectiles. When these energetic molecules collide with surrounding molecules/ atoms it causes the increase in temperature and release of energy.