Because chemical potential or molar free energy determines when a substance will move from one chemical region to another, it often is referred to as an escaping tendency.

When I₂ is concentrated in the ether layer, it has a high free energy per mole, or a high escaping tendency. If the escaping tendency of I₂ in water is lower because the concentration there is low, then iodine will diffuse from ether to water until its escaping tendencies in the two phases are the same.

This relationship between free energy and escaping tendency is especially helpful in understanding some of the properties of solutions, and these are the subject of the first part of this chapter.

lodine molecules will partition themselves between the ether and water layers until their molar free energy, or escaping tendency, is the same in each layer