Hello everybody, First, sorry for the bad english, it is not my language. I have a few theoretical problems and I would be very thankful if you helped me. 1º: I see the graphic about covalent bonds and potential energy a lot of times and they always say that potential energy decreases at the formation of the molecule >>> ex: http://chemistry.tutorvista.com/organic-chemistry/chemical-bonds.html In my textbook it says: '' the attractive forces between nuclei of the atoms and their electrons tend to approximate the two atoms and lower the potential energy of their system'' But my doubt is: If two atoms form a molecule, their kinetic energy should decrease and the potential energy rise due to the bond that ''stores'' that energy? Then they go to a state of less kinetic energy (more stable). When they say the potential energy decreases they are ignoring the fact that what's important is the absolute value and in fact it's increasing like the graphs of velocity, that even if goes to negative It's increasing but at an another direction (analogy).The minus sign only shows that is potential. I'm confusing it all or not? Please help ^^ 2º Doubt: In a exothermic reaction, the energy released from the system comes from the difference of temperature, comes from bonds forming or from both?