Exothermic chemical reactions

[Anup-Karki]

How is heat evolved during exothermic chemical reactiions?

[steveb]

basically a reaction is exothermic when the energy released from the production of new bonds exceeds the energy required to break the existing bonds. Sorry thats basic it's a while since i did a level chemistry. I'm sure someone will give a more detailed answer!
Steve

[wildwood]

According to wiki "the energy needed for the reaction to occur is less than the total energy released. As a result of this, the extra energy is released, usually in the form of heat." which is basically what steveb said.

I do wish you people wouldn't keep posting these interesting questions. I waste half my free time getting caught up in the intricacies of science ;-) I just wish I'd paid more attention in school.