Final answer:
The sample of water vapor at 110°C has the least average kinetic energy because kinetic energy is proportional to temperature, making it the lowest among the given temperatures.
Step-by-step explanation:
The student asks which of the three samples of water vapor – at temperatures of 110°C, 120°C, and 125°C – has the least average kinetic energy. According to kinetic molecular theory (KMT), the average kinetic energy of the particles in a substance is a direct function of temperature. Therefore, the sample with the lowest temperature will have the least average kinetic energy.
In this case, the sample of water vapor at 110°C would have the least average kinetic energy amongst the three provided temperatures. It is because kinetic energy is proportional to the absolute temperature of the particles within a substance, and a lower temperature equates to lower kinetic energy for the particles in a gas.