Interactions when goals overlap

It seems obvious that the scenarios described so far fail to explain the origin of cells and the existence of viruses. Therefore, to advance a step further toward these goals, one assumes that the aforementioned scenarios had to overlap with each other. This is feasible when the different niches that each contained one of the world scenarios had the opportunity to interact with each other. It is likely that Nature played with all the possible combinations. The difficulty here is to decide which one was first and which one followed. 

The physical forces described above aptly account for most molecular interactions in the gas phase. We now direct our discussion toward the condensed phases. Sohds and liquids form when the net attractive intermolecular forces are stronger than the thermal energy in the system and, consequently, hold the molecules together. While the force of attraction can sometimes be attributed to the electrostatic and van der Waals interactions described above, chemical forces also frequently play a role in condensed phases. Chemical forces are based on the nature of covalent electrons, the concept of the chemical bond, and the formation of new chemical species. The main difference between chemical and physical forces is that chemical forces saturate whereas physical forces do not, since chemical interactions are specific to the electronic wavefunc-tions of the chemical species involved. Indeed, a complete quantitative description of chemical interactions involves solution of the Schrodinger equation to describe the overlap of the molecular orbitals involved. We will consider chemical interactions only qualitatively. The goal of this discussion is to realize that there may be other important forces that govern the behavior of solids and liquids and to get a flavor of what these forces might be. 

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