Final answer:
B) -100°C. The molecules in a one gram sample of water would have the lowest average kinetic energy at -100°C (173 K), as this temperature is closest to absolute zero and lower than the other options provided.
Step-by-step explanation:
The temperature at which the molecules in a one gram sample of water would have the lowest average kinetic energy is at -100°C (Option B). This is because the average kinetic energy of a substance's particles is directly proportional to the temperature on the Kelvin scale.
Since absolute zero (0 K) is the point where all molecular motion ceases, any temperature above this but still lower than others will have the lowest kinetic energy. In the options given, -100°C is equivalent to 173 K, which is lower than both 5°C (278 K) and 100 K.
Therefore, of the given options, 173 K (or -100°C) is closest to absolute zero and would exhibit the lowest average kinetic energy.
The lowest average kinetic energy of the molecules in a one gram sample of water would be at absolute zero, which is the temperature at which all molecular motion ceases.
Absolute zero is approximately -273 °C or 0 K. At this temperature, the molecules in the water would have the least amount of energy and would be virtually motionless.