Can somebody explain in details. If we look at a hydrogen molecule where both of the electrons are in the bonding orbitals, and you increase the temperature( which are photons) slowly, will the hydrogen molecule move faster? And what will happend to the electrons in the bonding orbital?

Sure the thermal motions involve photons for transitions but the energy levels for the bonding are much higher. There is no interaction. What happens to the hydrogen molecule is it rotates, and translates and vibrates in quantum jumps like changing gears in your car but these don't couple to the electronic energies. However you can get mass displacements in the nuclei caused by electronic forces ie visible photon range and these can degrade into thermal energy.

ok , this question is now consists of many questions  as such :-what happen to the molecules of hydrogen if we apply heat to it ? the immediate answer emerges is that since heat is  energy and energy can not be lost according to the first law of thermodynamics then the only way is that it is transformed to kinetic energy then molecules move faster either vibrate more or translate and move far from each other till the change their state , but what happen to the atoms the same logic the  applies  to the atoms but atoms have electrons evolving in orbits also they will vibrate and already they are rotating and the translate to make another high orbits and if the applied is continued to be more and more then the atom at the end the atom will be freed form electrons, bur some question may come out like what happen to the bonding's between these atoms the bonding must be look as electrostatic attraction forces between the same kind or another kind and as stated that the atoms when treated with high heat or energy  the translate and over come these bonding forces to understand the above said in details please refer to the following article :-Let's define temperature to be a measure the kinetic energy of the atom. A single atom has limited numbers of ways it can store energy. It can translate in X, Y or Z. It can't really rotate (well it does rotate, but it takes so little energy to make it rotate that we can ignore it). It can't vibrate. It does have electronic modes where adding energy can increase the orbits of the electrons. So let's define a ground state. This is the point at which there is no energy stored in the transnational or electronic modes. Since there is zero energy and we defined temperature to be a measure of energy, this state is at 0K or absolute zero.As we add heat to the atom, the atom begins to translate around. The more heat that is added, the faster the translation. We keep adding heat, it translates faster and faster. There is more kinetic energy, so the temperature is higher. Eventually we add so much energy that now it can go into the electronic modes. Electrons start to move to higher orbits. Eventually we could add so much that they are set free and the atom loses some, or all, of it's electrons. We can still call the energy stored in the electronic modes as a temperature, but it's not the same as what we are used to. You would now have two temperatures, one transnational and one electronic.The same principles apply to molecules, except those can rotate and vibrate as well. States of matterUltimately, it doesn't make sense to look at an atom as a solid, liquid or gas. It's just an atom. A collection of atoms becomes a solid, liquid or gas. How the atoms move about is http://physics.stackexchange.com/questions/tagged/kinetic-theory. This theory has differences for solids, liquids and gases and each differs in various ways.But let's look at how the states change. In a solid, you have a bunch of atoms that can be thought of as masses connected by springs. As heat is added to the system, the atoms begin to vibrate in the lattice of springs. As more heat is added, they vibrate enough to break the springs. This is when the solid begins to melt and turn to a liquid.Now you have a liquid where the atoms are all moving around but they aren't free to move wherever they want. More heat is added to the system and the atoms begin to translate faster and faster. Eventually they translate fast enough to overcome the forces that are holding them together in a liquid. Now they fly free and are a gas. So ultimately, heat is energy that makes atoms and molecules move in some way. They may translate, rotate, vibrate, or the electrons may begin moving around depending on how much heat is there and what configuration the molecule has.http://physics.stackexchange.com/a/71912citehttp://physics.stackexchange.com/posts/71912/edit