The Natural Tendency toward Mixing

In the chapter-opening photograph of dye dispersing in water, is entropy 

Suppose we have 02(g) and Ar(g) separated by a barrier, as in FIGURE 13.1. If the barrier is removed, the gases mix to form a solution. The molecules experience very little in the way of intermolecular interactions and behave like ideal gas particles. As a result, their molecular motion causes them to spread through the larger volume, and a gaseous solution is formed. 

Which two thermodynamic quantities determine whether or not a process is 

Any of the various intermolecular forces discussed in Chapter 11 can operate between solute and solvent particles in a solution. These forces are summarized in FIGURE 13.2. Dispersion forces, for example, dominate when one nonpolar substance, such as C7H16, dissolves in another, such as C5H12, and ion-dipole forces dominate in solutions of ionic substances in water. 

Why does the oxygen atom in H2O point toward Na+ in the ion-dipole interaction  

Three kinds of intermolecular interactions are involved in solution formation  

---