| | Glucose exists in two different configurations (called anomers) that only differ in the spatial arrangement of the elements in its molecules (the elemental composition is the same). The configurations are called alpha-glucose and beta-glucose, respectively. Originally, we only have a-glucose. If we dissolve it in water, part of it will change slowly into b-glucose (Fig. 1). Glucose dissolved in water rotates the plane of polarized light passing through it. The effect is different for alpha and beta glucose. So as the concentrations change, the angel of rotation changes (this effect can be measured; Fig. 2).
Interpretation A configuration of glucose has a tendency or drive to change. The strength of this tendency can be expressed in terms of the chemical potential, just as we did in the case of the tendency of a substance to disperse. alpha-glucose and beta-glucose have different chemical potentials, and these potentials also depend upon concentration. If there is a difference in chemical potential, there is a tendency to change. Once the chemical potentials have become equal, this chemical driving force stops. The experiments shows that the chemical potentials of alpha-glucose and beta-glucose become equal at different concentrations. This behavior is the same as that observed for the tendency to disperse (see Phenomenon 4). | 
Investigation 5 |
