Final answer:
The slowest diffusion of the purple crystal in the beaker of water would occur in the beaker with the lowest temperature, as diffusion rate increases with temperature and is slower for more massive molecules.
Step-by-step explanation:
When Charlie places one purple crystal in each of four beakers of water, the rate of diffusion of the crystal in the water will depend on various factors, such as temperature and the mass of the diffusing molecules. In this scenario, if we assume that all other conditions are equal, the slowest diffusion would be in the beaker with the lowest temperature or if the molecule of the purple crystal is more massive compared to others. This is because diffusion rate is inversely proportional to molecular mass, and it increases with temperature as the average molecular speed increases with temperature. Hence, the temperature of the beakers is crucial in determining the rate of diffusion, with lower temperatures resulting in slower diffusion.