Hi again, I have a couple of questions: 1) Nitrogen (N2) exists liquid and solid. The molecules bond with van der Waals forces. What's the difference between liquid and solid state? Just quantity of van der Waals forces? 2) When is nitrogen ready for freezing? When atoms have such a heat kinetic energy, that they bring near enough and the induced electric field is strong enough to induce dipoles in another molecules? Or where is the breaking point? 3) Dipole's interaction is attractive. What's the repulsive interactions, in order atoms don't collapse? 4) One more question here (LINK). I hope I'm not so much annoying with that. :shy: Thanks for every single advice or remark.