This process works because different dye particles dissolve and travel at different __________ . What word completes the gap?

The word that completes the gap is "rates."

This process works because different dye particles dissolve and travel at different rates. In chromatography, for example, various substances are separated based on how quickly they move through a medium when carried by a solvent. Substances that interact more strongly with the medium will travel more slowly, while those that do not interact as much will move faster. This difference in movement, or rate of travel, allows for the separation and identification of the different components in a mixture. The varying solubilities and affinities of the dye particles for the stationary phase and the mobile phase result in distinctive separation patterns based on their individual rates.