To investigate the connection between kinetic energy and temperature, the most appropriate experimental setup would be:
placing one drop of food coloring in a cup with 50 mL of water at 10ºC; placing one drop of food coloring in a second cup with 50 mL of water at 40ºC.
This setup allows the student to compare the diffusion rate of the food coloring in water at different temperatures (10ºC and 40ºC). Since higher temperatures correspond to higher kinetic energy, the difference in how quickly the food coloring spreads in the water would provide insight into the relationship between temperature and kinetic energy.