Hydrogen molecules phase-change rule

Like dissolves like is an extremely useful rule of thumb. Structurally similar molecules associate with a similar intermolecular interaction. Thus, a molecule in the liquid can be substituted by a structurally similar molecule, without a major change in intermolecular interactions. Ethanol dissolves in water because major interactions holding water molecules to each other and those of the ethanol are very similar, hydrogen bond interactions. On the other hand, water and carbon tetrachloride make a biphase system. The carbon tetrachloride molecules are cast aside because they cannot make enough hydrogen bonding interaction with water molecules to hold the molecules in the water phase. Thus, the carbon tetrachloride molecules hold themselves in the other phase by van der Waals interaction. 

---