Final answer:
The colorless result of shaking the phycocyanin solution could be due to a physical change, such as the denaturing of pigment molecules or the introduction of air, which affects how the solution absorbs or reflects light.
Step-by-step explanation:
The student's observation that a solution containing phycocyanin becomes colorless upon vigorous shaking may relate to the principle of equilibrium demonstrated in chemical reactions, like the one between N₂O₄ gas and NO₂ gas, where changes in pressure and concentration can affect the color.
In the context of the student's experiment, it's possible that the pigment molecules were either denatured or the shaking caused the formation of bubbles (introduction of air), which disrupted the ability of the solution to absorb or reflect light in the same way, leading to a temporary or permanent change in the color of the solution.
This assumes there are no chemical reactions occurring that would account for the decolorization, such as a reaction with oxygen. Without more information on the chemical stability of phycocyanin, we can hypothesize that this is a physical change similar to the kind observed when mixing a green solution with a colorless one, where the overall color dilutes but no chemical change occurs.