A laboratory experiment has been developed to illustrate the transformation of silver nanoparticles (Ag NPs) in water containing phosphate anions. The experiment, conducted by high school students, involved hands-on learning to synthesize and characterize Ag NPs via ultraviolet-visible (UV-vis) spectroscopy. This was followed by a UV-vis probe of the interaction of Ag NPs with phosphate anions. The observations of the color and shift in the absorption spectrum of NPs were explored to help students understand the transformation of NPs in water containing anions.